LibGfx: Add BMP loader

Adds an *almost fully featured BMP loader to process .bmp files.

Features:
- All header formats are supported
- Full RLE4/8/24 support
- Color scaling (e.g. distributing a 5-bit color throughout the 8-bit
color spectrum, so 5-bit white is still 0xffffff)
- Full BITMASK/ALPHABITMASK support

*Not included:
- 1D Huffman compression. Good luck actually finding a bmp in the wild
that uses this
- Use of any field in the V4/V5 header. Color spaces? Endpoints? No
thanks :)

This loader was tested with the images at
https://entropymine.com/jason/bmpsuite/bmpsuite/html/bmpsuite.html. This
loader correctly displays 81 out of the 90 total images (for reference,
firefox displays 64 correctly). Note that not rendering the images at
the bottom is counted as displaying correctly.

8 files changed, 1477 insertions, 15 deletions

diff --git a/Libraries/LibGfx/BMPLoader.cpp b/Libraries/LibGfx/BMPLoader.cpp
new file mode 100644
index 0000000000..a6c82ca15d
--- /dev/null
+++ b/Libraries/LibGfx/BMPLoader.cpp
@@ -0,0 +1,1315 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <AK/LexicalPath.h>
+#include <AK/MappedFile.h>
+#include <LibGfx/BMPLoader.h>
+
+#define BMP_DEBUG 0
+
+#define IF_BMP_DEBUG(x) \
+    if (BMP_DEBUG)      \
+    x
+
+namespace Gfx {
+
+const u8 bmp_header_size = 14;
+const u32 color_palette_limit = 1024;
+
+// Compression flags
+struct Compression {
+    enum : u32 {
+        RGB = 0,
+        RLE8,
+        RLE4,
+        BITFIELDS,
+        RLE24, // doubles as JPEG for V4+, but that is unsupported
+        PNG,
+        ALPHABITFIELDS,
+        CMYK = 11,
+        CMYKRLE8,
+        CMYKRLE4,
+    };
+};
+
+struct DIBCore {
+    // u16 for BITMAPHEADERCORE, but i32 for everything else. If the dib type is
+    // BITMAPHEADERCORE, this is range checked.
+    i32 width;
+    i32 height;
+    u16 bpp;
+};
+
+struct DIBInfo {
+    u32 compression { Compression::RGB };
+    u32 image_size { 0 };
+    i32 horizontal_resolution { 0 };
+    i32 vertical_resolution { 0 };
+    u32 number_of_palette_colors { 0 };
+    u32 number_of_important_palette_colors { number_of_palette_colors };
+
+    // Introduced in the BITMAPV2INFOHEADER and would ideally be stored in the
+    // DIBV2 struct, however with a compression value of BI_BITFIELDS or
+    // BI_ALPHABITFIELDS, these can be specified with the Info header.
+    Vector<u32> masks;
+    Vector<i8> mask_shifts;
+    Vector<u8> mask_sizes;
+};
+
+struct DIBOSV2 {
+    u16 recording;
+    u16 halftoning;
+    u16 size1;
+    u16 size2;
+};
+
+template<typename T>
+struct Endpoint {
+    T x;
+    T y;
+    T z;
+};
+
+struct DIBV4 {
+    u32 color_space { 0 };
+    Endpoint<i32> red_endpoint { 0, 0, 0 };
+    Endpoint<i32> green_endpoint { 0, 0, 0 };
+    Endpoint<i32> blue_endpoint { 0, 0, 0 };
+    Endpoint<u32> gamma_endpoint { 0, 0, 0 };
+};
+
+struct DIBV5 {
+    u32 intent { 0 };
+    u32 profile_data { 0 };
+    u32 profile_size { 0 };
+};
+
+struct DIB {
+    DIBCore core;
+    DIBInfo info;
+    DIBOSV2 osv2;
+    DIBV4 v4;
+    DIBV5 v5;
+};
+
+enum class DIBType {
+    Core = 0,
+    OSV2Short,
+    OSV2,
+    Info,
+    V2,
+    V3,
+    V4,
+    V5
+};
+
+struct BMPLoadingContext {
+    enum class State {
+        NotDecoded = 0,
+        HeaderDecoded,
+        DIBDecoded,
+        ColorTableDecoded,
+        PixelDataDecoded,
+        Error,
+    };
+    State state { State::NotDecoded };
+
+    const u8* data { nullptr };
+    size_t data_size { 0 };
+    u32 data_offset { 0 };
+
+    DIB dib;
+    DIBType dib_type;
+
+    Vector<u32> color_table;
+    RefPtr<Gfx::Bitmap> bitmap;
+
+    u8 dib_size() const
+    {
+        switch (dib_type) {
+        case DIBType::Core:
+            return 12;
+        case DIBType::OSV2Short:
+            return 16;
+        case DIBType::OSV2:
+            return 64;
+        case DIBType::Info:
+            return 40;
+        case DIBType::V2:
+            return 52;
+        case DIBType::V3:
+            return 56;
+        case DIBType::V4:
+            return 108;
+        case DIBType::V5:
+            return 124;
+        }
+
+        ASSERT_NOT_REACHED();
+    }
+};
+
+static RefPtr<Bitmap> load_bmp_impl(const u8*, size_t);
+
+RefPtr<Gfx::Bitmap> load_bmp(const StringView& path)
+{
+    MappedFile mapped_file(path);
+    if (!mapped_file.is_valid())
+        return nullptr;
+    auto bitmap = load_bmp_impl((const u8*)mapped_file.data(), mapped_file.size());
+    if (bitmap)
+        bitmap->set_mmap_name(String::format("Gfx::Bitmap [%dx%d] - Decoded BMP: %s", bitmap->width(), bitmap->height(), LexicalPath::canonicalized_path(path).characters()));
+    return bitmap;
+}
+
+const LogStream& operator<<(const LogStream& out, Endpoint<i32> ep)
+{
+    return out << "(" << ep.x << ", " << ep.y << ", " << ep.z << ")";
+}
+
+const LogStream& operator<<(const LogStream& out, Endpoint<u32> ep)
+{
+    return out << "(" << ep.x << ", " << ep.y << ", " << ep.z << ")";
+}
+
+class Streamer {
+public:
+    Streamer(const u8* data, size_t size)
+        : m_data_ptr(data)
+        , m_size_remaining(size)
+    {
+    }
+
+    u8 read_u8()
+    {
+        ASSERT(m_size_remaining >= 1);
+        m_size_remaining--;
+        return *(m_data_ptr++);
+    }
+
+    u16 read_u16()
+    {
+        return read_u8() | (read_u8() << 8);
+    }
+
+    u32 read_u24()
+    {
+        return read_u8() | (read_u8() << 8) | (read_u8() << 16);
+    }
+
+    i32 read_i32()
+    {
+        return static_cast<i32>(read_u16() | (read_u16() << 16));
+    }
+
+    u32 read_u32()
+    {
+        return read_u16() | (read_u16() << 16);
+    }
+
+    void drop_bytes(u8 num_bytes)
+    {
+        ASSERT(m_size_remaining >= num_bytes);
+        m_size_remaining -= num_bytes;
+        m_data_ptr += num_bytes;
+    }
+
+    bool at_end() const { return !m_size_remaining; }
+
+    bool has_u8() const { return m_size_remaining >= 1; }
+    bool has_u16() const { return m_size_remaining >= 2; }
+    bool has_u24() const { return m_size_remaining >= 3; }
+    bool has_u32() const { return m_size_remaining >= 4; }
+
+    size_t remaining() const { return m_size_remaining; }
+    void set_remaining(size_t remaining) { m_size_remaining = remaining; }
+
+private:
+    const u8* m_data_ptr { nullptr };
+    size_t m_size_remaining { 0 };
+};
+
+// Lookup table for distributing all possible 2-bit numbers evenly into 8-bit numbers
+u8 scaling_factors_2bit[4] = {
+    0x00,
+    0x55,
+    0xaa,
+    0xff,
+};
+
+// Lookup table for distributing all possible 3-bit numbers evenly into 8-bit numbers
+u8 scaling_factors_3bit[8] = {
+    0x00,
+    0x24,
+    0x48,
+    0x6d,
+    0x91,
+    0xb6,
+    0xdb,
+    0xff,
+};
+
+u8 scale_masked_8bit_number(u8 number, u8 bits_set)
+{
+    // If there are more than 4 bit set, an easy way to scale the number is to
+    // just copy the most significant bits into the least significant bits
+    if (bits_set >= 4)
+        return number | (number >> bits_set);
+    if (!bits_set)
+        return 0;
+    if (bits_set == 1)
+        return number ? 0xff : 0;
+    if (bits_set == 2)
+        return scaling_factors_2bit[number >> 6];
+    return scaling_factors_3bit[number >> 5];
+}
+
+u8 get_scaled_color(u32 data, u8 mask_size, i8 mask_shift)
+{
+    // A negative mask_shift indicates we actually need to left shift
+    // the result in order to get out a valid 8-bit color (for example, the blue
+    // value in an RGB555 encoding is XXXBBBBB, which needs to be shifted to the
+    // left by 3, hence it would have a "mask_shift" value of -3).
+    if (mask_shift < 0)
+        return scale_masked_8bit_number(data << -mask_shift, mask_size);
+    return scale_masked_8bit_number(data >> mask_shift, mask_size);
+}
+
+// Scales an 8-bit number with "mask_size" bits set (and "8 - mask_size" bits
+//   ignored). This function scales the number appropriately over the entire
+//   256 value color spectrum.
+// Note that a much simpler scaling can be done by simple bit shifting. If you
+//   just ignore the bottom 8-mask_size bits, then you get *close*. However,
+//   consider, as an example, a 5 bit number (so the bottom 3 bits are ignored).
+//   The purest white you could get is 0xf8, which is 248 in RGB-land. We need
+//   to scale the values in order to reach the proper value of 255.
+u32 int_to_scaled_rgb(BMPLoadingContext& context, u32 data)
+{
+    u8 r = get_scaled_color(data & context.dib.info.masks[0], context.dib.info.mask_sizes[0], context.dib.info.mask_shifts[0]);
+    u8 g = get_scaled_color(data & context.dib.info.masks[1], context.dib.info.mask_sizes[1], context.dib.info.mask_shifts[1]);
+    u8 b = get_scaled_color(data & context.dib.info.masks[2], context.dib.info.mask_sizes[2], context.dib.info.mask_shifts[2]);
+    u32 color = (r << 16) | (g << 8) | b;
+
+    if (context.dib.info.masks.size() == 4) {
+        // The bitmap has an alpha mask
+        u8 a = get_scaled_color(data & context.dib.info.masks[3], context.dib.info.mask_sizes[3], context.dib.info.mask_shifts[3]);
+        color |= (a << 24);
+    } else {
+        color |= 0xff000000;
+    }
+
+    return color;
+}
+
+void populate_dib_mask_info(BMPLoadingContext& context)
+{
+    if (context.dib.info.masks.is_empty())
+        return;
+
+    // Mask shift is the number of right shifts needed to align the MSb of the
+    //   mask to the MSb of the LSB.
+    // Mask size is the number of set bits in the mask. This is required for
+    //   color scaling (for example, ensuring that a 4-bit color value spans the
+    //   entire 256 value color spectrum.
+    auto& masks = context.dib.info.masks;
+    auto& mask_shifts = context.dib.info.mask_shifts;
+    auto& mask_sizes = context.dib.info.mask_sizes;
+
+    if (!mask_shifts.is_empty() && !mask_sizes.is_empty())
+        return;
+
+    ASSERT(mask_shifts.is_empty() && mask_sizes.is_empty());
+
+    mask_shifts.ensure_capacity(masks.size());
+    mask_sizes.ensure_capacity(masks.size());
+
+    for (size_t i = 0; i < masks.size(); ++i) {
+        u32 mask = masks[i];
+        u8 shift = 0;
+        u8 size = 0;
+        bool found_set_bit = false;
+
+        while (shift <= 32) {
+            u8 bit = (mask >> shift) & 0x1;
+            if (found_set_bit)
+                size++;
+            if (!found_set_bit && bit) {
+                found_set_bit = true;
+            } else if (found_set_bit && !bit) {
+                break;
+            }
+            shift++;
+        }
+
+        if (shift > 32) {
+            mask_shifts.append(0);
+            mask_sizes.append(0);
+        } else {
+            mask_shifts.append(shift - 8);
+            mask_sizes.append(size);
+        }
+    }
+}
+
+static bool check_for_invalid_bitmask_combinations(BMPLoadingContext& context)
+{
+    auto& bpp = context.dib.core.bpp;
+    auto& compression = context.dib.info.compression;
+
+    if (compression == Compression::ALPHABITFIELDS && context.dib_type != DIBType::Info)
+        return false;
+
+    switch (context.dib_type) {
+    case DIBType::Core:
+        if (bpp == 2 || bpp == 16 || bpp == 32)
+            return false;
+        break;
+    case DIBType::Info:
+        if ((compression == Compression::BITFIELDS || compression == Compression::ALPHABITFIELDS) && bpp != 16 && bpp != 32)
+            return false;
+        break;
+    case DIBType::OSV2Short:
+    case DIBType::OSV2:
+    case DIBType::V2:
+    case DIBType::V3:
+    case DIBType::V4:
+    case DIBType::V5:
+        if (compression == Compression::BITFIELDS && bpp != 16 && bpp != 32)
+            return false;
+        break;
+    }
+
+    return true;
+}
+
+static bool set_dib_bitmasks(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!check_for_invalid_bitmask_combinations(context))
+        return false;
+
+    auto& bpp = context.dib.core.bpp;
+    if (bpp <= 8 || bpp == 24)
+        return true;
+
+    auto& compression = context.dib.info.compression;
+    auto& type = context.dib_type;
+
+    if (type > DIBType::OSV2 && bpp == 16 && compression == Compression::RGB) {
+        context.dib.info.masks.append({ 0x7c00, 0x03e0, 0x001f });
+        context.dib.info.mask_shifts.append({ 7, 2, -3 });
+        context.dib.info.mask_sizes.append({ 5, 5, 5 });
+
+        populate_dib_mask_info(context);
+    } else if (type == DIBType::Info && (compression == Compression::BITFIELDS || compression == Compression::ALPHABITFIELDS)) {
+        // Consume the extra BITFIELDS bytes
+        auto number_of_mask_fields = compression == Compression::ALPHABITFIELDS ? 4 : 3;
+        streamer.set_remaining(number_of_mask_fields * 4);
+
+        for (auto i = 0; i < number_of_mask_fields; i++)
+            context.dib.info.masks.append(streamer.read_u32());
+
+        populate_dib_mask_info(context);
+    } else if (type >= DIBType::V2 && compression == Compression::BITFIELDS) {
+        populate_dib_mask_info(context);
+    }
+
+    return true;
+}
+
+static bool decode_bmp_header(BMPLoadingContext& context)
+{
+    if (context.state == BMPLoadingContext::State::Error)
+        return false;
+
+    if (context.state >= BMPLoadingContext::State::HeaderDecoded)
+        return true;
+
+    if (!context.data || context.data_size < bmp_header_size) {
+        IF_BMP_DEBUG(dbg() << "Missing BMP header");
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    Streamer streamer(context.data, bmp_header_size);
+
+    u16 header = streamer.read_u16();
+    if (header != 0x4d42) {
+        IF_BMP_DEBUG(dbgprintf("BMP has invalid magic header number: %04x\n", header));
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    // The reported size of the file in the header is actually not important
+    // for decoding the file. Some specifications say that this value should
+    // be the size of the header instead, so we just rely on the known file
+    // size, instead of a possibly-correct-but-also-possibly-incorrect reported
+    // value of the file size.
+    streamer.drop_bytes(4);
+
+    // Ingore reserved bytes
+    streamer.drop_bytes(4);
+    context.data_offset = streamer.read_u32();
+    context.state = BMPLoadingContext::State::HeaderDecoded;
+
+    IF_BMP_DEBUG(dbg() << "BMP data size: " << context.data_size);
+    IF_BMP_DEBUG(dbg() << "BMP data offset: " << context.data_offset);
+
+    return true;
+}
+
+static bool decode_bmp_core_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    auto& core = context.dib.core;
+
+    // The width and height are u16 fields in the actual BITMAPCOREHEADER format.
+    if (context.dib_type == DIBType::Core) {
+        core.width = streamer.read_u16();
+        core.height = streamer.read_u16();
+    } else {
+        core.width = streamer.read_i32();
+        core.height = streamer.read_i32();
+    }
+
+    if (core.width < 0) {
+        IF_BMP_DEBUG(dbg() << "BMP has a negative width: " << core.width);
+        return false;
+    }
+
+    auto color_planes = streamer.read_u16();
+    if (color_planes != 1) {
+        IF_BMP_DEBUG(dbg() << "BMP has an invalid number of color planes: " << color_planes);
+        return false;
+    }
+
+    core.bpp = streamer.read_u16();
+
+    switch (core.bpp) {
+    case 1:
+    case 2:
+    case 4:
+    case 8:
+    case 16:
+    case 24:
+    case 32:
+        break;
+    default:
+        IF_BMP_DEBUG(dbg() << "BMP has an invalid bpp: " << core.bpp);
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    IF_BMP_DEBUG(dbg() << "BMP width: " << core.width);
+    IF_BMP_DEBUG(dbg() << "BMP height: " << core.height);
+    IF_BMP_DEBUG(dbg() << "BMP bits_per_pixel: " << core.bpp);
+
+    return true;
+}
+
+static bool decode_bmp_osv2_dib(BMPLoadingContext& context, Streamer& streamer, bool short_variant = false)
+{
+    auto& core = context.dib.core;
+
+    core.width = streamer.read_u32();
+    core.height = streamer.read_u32();
+
+    if (core.width < 0) {
+        IF_BMP_DEBUG(dbg() << "BMP has a negative width: " << core.width);
+        return false;
+    }
+
+    auto color_planes = streamer.read_u16();
+    if (color_planes != 1) {
+        IF_BMP_DEBUG(dbg() << "BMP has an invalid number of color planes: " << color_planes);
+        return false;
+    }
+
+    core.bpp = streamer.read_u16();
+
+    IF_BMP_DEBUG(dbg() << "BMP width: " << core.width);
+    IF_BMP_DEBUG(dbg() << "BMP height: " << core.height);
+    IF_BMP_DEBUG(dbg() << "BMP bpp: " << core.bpp);
+
+    if (short_variant)
+        return true;
+
+    auto& info = context.dib.info;
+    auto& osv2 = context.dib.osv2;
+
+    info.compression = streamer.read_u32();
+    info.image_size = streamer.read_u32();
+    info.horizontal_resolution = streamer.read_u32();
+    info.vertical_resolution = streamer.read_u32();
+    info.number_of_palette_colors = streamer.read_u32();
+    info.number_of_important_palette_colors = streamer.read_u32();
+
+    if (info.number_of_palette_colors > color_palette_limit || info.number_of_important_palette_colors > color_palette_limit) {
+        IF_BMP_DEBUG(dbg() << "BMP header indicates too many palette colors: " << info.number_of_palette_colors);
+        return false;
+    }
+
+    // Units (2) + reserved (2)
+    streamer.drop_bytes(4);
+
+    osv2.recording = streamer.read_u16();
+    osv2.halftoning = streamer.read_u16();
+    osv2.size1 = streamer.read_u32();
+    osv2.size2 = streamer.read_u32();
+
+    // ColorEncoding (4) + Identifier (4)
+    streamer.drop_bytes(8);
+
+    IF_BMP_DEBUG(dbg() << "BMP compression: " << info.compression);
+    IF_BMP_DEBUG(dbg() << "BMP image size: " << info.image_size);
+    IF_BMP_DEBUG(dbg() << "BMP horizontal res: " << info.horizontal_resolution);
+    IF_BMP_DEBUG(dbg() << "BMP vertical res: " << info.vertical_resolution);
+    IF_BMP_DEBUG(dbg() << "BMP colors: " << info.number_of_palette_colors);
+    IF_BMP_DEBUG(dbg() << "BMP important colors: " << info.number_of_important_palette_colors);
+
+    return true;
+}
+
+ALWAYS_INLINE bool is_supported_compression_format(BMPLoadingContext& context, u8 compression)
+{
+    return compression == Compression::RGB || compression == Compression::BITFIELDS
+        || compression == Compression::ALPHABITFIELDS || compression == Compression::RLE8
+        || compression == Compression::RLE4 || (compression == Compression::RLE24 && context.dib_type <= DIBType::OSV2);
+}
+
+static bool decode_bmp_info_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!decode_bmp_core_dib(context, streamer))
+        return false;
+
+    auto& info = context.dib.info;
+
+    auto compression = streamer.read_u32();
+    info.compression = compression;
+    if (!is_supported_compression_format(context, compression)) {
+        IF_BMP_DEBUG(dbg() << "BMP has unsupported compression value: " << compression);
+        return false;
+    }
+
+    info.image_size = streamer.read_u32();
+    info.horizontal_resolution = streamer.read_i32();
+    info.vertical_resolution = streamer.read_i32();
+    info.number_of_palette_colors = streamer.read_u32();
+    info.number_of_important_palette_colors = streamer.read_u32();
+
+    if (info.number_of_palette_colors > color_palette_limit || info.number_of_important_palette_colors > color_palette_limit) {
+        IF_BMP_DEBUG(dbg() << "BMP header indicates too many palette colors: " << info.number_of_palette_colors);
+        return false;
+    }
+
+    if (info.number_of_important_palette_colors == 0)
+        info.number_of_important_palette_colors = info.number_of_palette_colors;
+
+    IF_BMP_DEBUG(dbg() << "BMP compression: " << info.compression);
+    IF_BMP_DEBUG(dbg() << "BMP image size: " << info.image_size);
+    IF_BMP_DEBUG(dbg() << "BMP horizontal resolution: " << info.horizontal_resolution);
+    IF_BMP_DEBUG(dbg() << "BMP vertical resolution: " << info.vertical_resolution);
+    IF_BMP_DEBUG(dbg() << "BMP palette colors: " << info.number_of_palette_colors);
+    IF_BMP_DEBUG(dbg() << "BMP important palette colors: " << info.number_of_important_palette_colors);
+
+    return true;
+}
+
+static bool decode_bmp_v2_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!decode_bmp_info_dib(context, streamer))
+        return false;
+
+    context.dib.info.masks.append(streamer.read_u32());
+    context.dib.info.masks.append(streamer.read_u32());
+    context.dib.info.masks.append(streamer.read_u32());
+
+    IF_BMP_DEBUG(dbgprintf("BMP red mask: %08x\n", context.dib.info.masks[0]));
+    IF_BMP_DEBUG(dbgprintf("BMP green mask: %08x\n", context.dib.info.masks[1]));
+    IF_BMP_DEBUG(dbgprintf("BMP blue mask: %08x\n", context.dib.info.masks[2]));
+
+    return true;
+}
+
+static bool decode_bmp_v3_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!decode_bmp_v2_dib(context, streamer))
+        return false;
+
+    // There is zero documentation about when alpha masks actually get applied.
+    // Well, there's some, but it's not even close to comprehensive. So, this is
+    // in no way based off of any spec, it's simply based off of the BMP test
+    // suite results.
+    if (context.dib.info.compression == Compression::ALPHABITFIELDS) {
+        context.dib.info.masks.append(streamer.read_u32());
+        IF_BMP_DEBUG(dbgprintf("BMP alpha mask: %08x\n", context.dib.info.masks[3]));
+    } else if (context.dib_size() >= 56 && context.dib.core.bpp >= 16) {
+        auto mask = streamer.read_u32();
+        if ((context.dib.core.bpp == 32 && mask != 0) || context.dib.core.bpp == 16) {
+            context.dib.info.masks.append(mask);
+            IF_BMP_DEBUG(dbgprintf("BMP alpha mask: %08x\n", mask));
+        }
+    } else {
+        streamer.drop_bytes(4);
+    }
+
+    return true;
+}
+
+static bool decode_bmp_v4_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!decode_bmp_v3_dib(context, streamer))
+        return false;
+
+    auto& v4 = context.dib.v4;
+    v4.color_space = streamer.read_u32();
+    v4.red_endpoint = { streamer.read_i32(), streamer.read_i32(), streamer.read_i32() };
+    v4.green_endpoint = { streamer.read_i32(), streamer.read_i32(), streamer.read_i32() };
+    v4.blue_endpoint = { streamer.read_i32(), streamer.read_i32(), streamer.read_i32() };
+    v4.gamma_endpoint = { streamer.read_u32(), streamer.read_u32(), streamer.read_u32() };
+
+    IF_BMP_DEBUG(dbg() << "BMP color space: " << v4.color_space);
+    IF_BMP_DEBUG(dbg() << "BMP red endpoint: " << v4.red_endpoint);
+    IF_BMP_DEBUG(dbg() << "BMP green endpoint: " << v4.green_endpoint);
+    IF_BMP_DEBUG(dbg() << "BMP blue endpoint: " << v4.blue_endpoint);
+    IF_BMP_DEBUG(dbg() << "BMP gamma endpoint: " << v4.gamma_endpoint);
+
+    return true;
+}
+
+static bool decode_bmp_v5_dib(BMPLoadingContext& context, Streamer& streamer)
+{
+    if (!decode_bmp_v4_dib(context, streamer))
+        return false;
+
+    auto& v5 = context.dib.v5;
+    v5.intent = streamer.read_u32();
+    v5.profile_data = streamer.read_u32();
+    v5.profile_size = streamer.read_u32();
+
+    IF_BMP_DEBUG(dbg() << "BMP intent: " << v5.intent);
+    IF_BMP_DEBUG(dbg() << "BMP profile data: " << v5.profile_data);
+    IF_BMP_DEBUG(dbg() << "BMP profile size: " << v5.profile_size);
+
+    return true;
+}
+
+static bool decode_bmp_dib(BMPLoadingContext& context)
+{
+    if (context.state == BMPLoadingContext::State::Error)
+        return false;
+
+    if (context.state >= BMPLoadingContext::State::DIBDecoded)
+        return true;
+
+    if (context.state < BMPLoadingContext::State::HeaderDecoded && !decode_bmp_header(context))
+        return false;
+
+    if (context.data_size < bmp_header_size + 4)
+        return false;
+
+    Streamer streamer(context.data + bmp_header_size, 4);
+    u32 dib_size = streamer.read_u32();
+
+    if (context.data_size < bmp_header_size + dib_size)
+        return false;
+
+    streamer.set_remaining(dib_size - 4);
+
+    IF_BMP_DEBUG(dbg() << "BMP dib size: " << dib_size);
+
+    bool error = false;
+
+    if (dib_size == 12) {
+        context.dib_type = DIBType::Core;
+        if (!decode_bmp_core_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 64) {
+        context.dib_type = DIBType::OSV2;
+        if (!decode_bmp_osv2_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 16) {
+        context.dib_type = DIBType::OSV2Short;
+        if (!decode_bmp_osv2_dib(context, streamer, true))
+            error = true;
+    } else if (dib_size == 40) {
+        context.dib_type = DIBType::Info;
+        if (!decode_bmp_info_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 52) {
+        context.dib_type = DIBType::V2;
+        if (!decode_bmp_v2_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 56) {
+        context.dib_type = DIBType::V3;
+        if (!decode_bmp_v3_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 108) {
+        context.dib_type = DIBType::V4;
+        if (!decode_bmp_v4_dib(context, streamer))
+            error = true;
+    } else if (dib_size == 124) {
+        context.dib_type = DIBType::V5;
+        if (!decode_bmp_v5_dib(context, streamer))
+            error = true;
+    } else {
+        IF_BMP_DEBUG(dbg() << "Unsupported BMP DIB size: " << dib_size);
+        error = true;
+    }
+
+    if (!error && !set_dib_bitmasks(context, streamer))
+        error = true;
+
+    if (error) {
+        IF_BMP_DEBUG(dbg() << "BMP has an invalid DIB");
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    context.state = BMPLoadingContext::State::DIBDecoded;
+
+    return true;
+}
+
+static bool decode_bmp_color_table(BMPLoadingContext& context)
+{
+    if (context.state == BMPLoadingContext::State::Error)
+        return false;
+
+    if (context.state < BMPLoadingContext::State::DIBDecoded && !decode_bmp_dib(context))
+        return false;
+
+    if (context.state >= BMPLoadingContext::State::ColorTableDecoded)
+        return true;
+
+    if (context.dib.core.bpp > 8) {
+        context.state = BMPLoadingContext::State::ColorTableDecoded;
+        return true;
+    }
+
+    auto bytes_per_color = context.dib_type == DIBType::Core ? 3 : 4;
+    u32 max_colors = 1 << context.dib.core.bpp;
+    auto size_of_color_table = context.data_offset - bmp_header_size - context.dib_size();
+
+    if (context.dib_type <= DIBType::OSV2) {
+        // Partial color tables are not supported, so the space of the color
+        // table must be at least enough for the maximum amount of colors
+        if (size_of_color_table < 3 * max_colors) {
+            // This is against the spec, but most viewers process it anyways
+            IF_BMP_DEBUG(dbg() << "BMP with CORE header does not have enough colors. Has: " << size_of_color_table << ", expected: " << (3 * max_colors));
+        }
+    }
+
+    Streamer streamer(context.data + bmp_header_size + context.dib_size(), size_of_color_table);
+    for (u32 i = 0; !streamer.at_end() && i < max_colors; ++i) {
+        if (bytes_per_color == 4) {
+            context.color_table.append(streamer.read_u32());
+        } else {
+            context.color_table.append(streamer.read_u24());
+        }
+    }
+
+    context.state = BMPLoadingContext::State::ColorTableDecoded;
+    return true;
+}
+
+struct RLEState {
+    enum : u8 {
+        PixelCount = 0,
+        PixelValue,
+        Meta, // Represents just consuming a null byte, which indicates something special
+    };
+};
+
+static bool uncompress_bmp_rle_data(BMPLoadingContext& context, ByteBuffer& buffer)
+{
+    // RLE-compressed images cannot be stored top-down
+    if (context.dib.core.height < 0) {
+        IF_BMP_DEBUG(dbg() << "BMP is top-down and RLE compressed");
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    Streamer streamer(context.data + context.data_offset, context.data_size);
+
+    auto compression = context.dib.info.compression;
+
+    u32 total_rows = static_cast<u32>(context.dib.core.height);
+    u32 total_columns = round_up_to_power_of_two(static_cast<u32>(context.dib.core.width), 4);
+    u32 column = 0;
+    u32 row = 0;
+    auto currently_consuming = RLEState::PixelCount;
+    i16 pixel_count = 0;
+
+    if (compression == Compression::RLE24) {
+        buffer = ByteBuffer::create_zeroed(total_rows * round_up_to_power_of_two(total_columns, 4) * 4);
+    } else {
+        buffer = ByteBuffer::create_zeroed(total_rows * round_up_to_power_of_two(total_columns, 4));
+    }
+
+    // Avoid as many if statements as possible by pulling out
+    // compression-dependent actions into separate lambdas
+    Function<u32()> get_buffer_index;
+    Function<bool(u32, bool)> set_byte;
+    Function<Optional<u32>()> read_byte;
+
+    if (compression == Compression::RLE8) {
+        get_buffer_index = [&]() -> u32 { return row * total_columns + column; };
+    } else if (compression == Compression::RLE4) {
+        get_buffer_index = [&]() -> u32 { return (row * total_columns + column) / 2; };
+    } else {
+        get_buffer_index = [&]() -> u32 { return (row * total_columns + column) * 3; };
+    }
+
+    if (compression == Compression::RLE8) {
+        set_byte = [&](u32 color, bool) -> bool {
+            if (column >= total_columns) {
+                column = 0;
+                row++;
+            }
+            auto index = get_buffer_index();
+            if (index >= buffer.size()) {
+                IF_BMP_DEBUG(dbg() << "BMP has badly-formatted RLE data");
+                return false;
+            }
+            buffer[index] = color;
+            column++;
+            return true;
+        };
+    } else if (compression == Compression::RLE24) {
+        set_byte = [&](u32 color, bool) -> bool {
+            if (column >= total_columns) {
+                column = 0;
+                row++;
+            }
+            auto index = get_buffer_index();
+            if (index >= buffer.size()) {
+                IF_BMP_DEBUG(dbg() << "BMP has badly-formatted RLE data");
+                return false;
+            }
+            ((u32&)buffer[index]) = color;
+            column++;
+            return true;
+        };
+    } else {
+        set_byte = [&](u32 byte, bool rle4_set_second_nibble) -> bool {
+            if (column >= total_columns) {
+                column = 0;
+                row++;
+            }
+
+            u32 index = get_buffer_index();
+            if (index >= buffer.size() || (rle4_set_second_nibble && index + 1 >= buffer.size())) {
+                IF_BMP_DEBUG(dbg() << "BMP has badly-formatted RLE data");
+                return false;
+            }
+
+            if (column % 2) {
+                buffer[index] |= byte >> 4;
+                if (rle4_set_second_nibble) {
+                    buffer[index + 1] |= byte << 4;
+                    column++;
+                }
+            } else {
+                if (rle4_set_second_nibble) {
+                    buffer[index] = byte;
+                    column++;
+                } else {
+                    buffer[index] |= byte & 0xf0;
+                }
+            }
+
+            column++;
+            return true;
+        };
+    }
+
+    if (compression == Compression::RLE24) {
+        read_byte = [&]() -> Optional<u32> {
+            if (!streamer.has_u24()) {
+                IF_BMP_DEBUG(dbg() << "BMP has badly-formatted RLE data");
+                return {};
+            }
+            return streamer.read_u24();
+        };
+    } else {
+        read_byte = [&]() -> Optional<u32> {
+            if (!streamer.has_u8()) {
+                IF_BMP_DEBUG(dbg() << "BMP has badly-formatted RLE data");
+                return {};
+            }
+            return streamer.read_u8();
+        };
+    }
+
+    while (true) {
+        u32 byte;
+
+        switch (currently_consuming) {
+        case RLEState::PixelCount:
+            if (!streamer.has_u8())
+                return false;
+            byte = streamer.read_u8();
+            if (!byte) {
+                currently_consuming = RLEState::Meta;
+            } else {
+                pixel_count = byte;
+                currently_consuming = RLEState::PixelValue;
+            }
+            break;
+        case RLEState::PixelValue: {
+            auto result = read_byte();
+            if (!result.has_value())
+                return false;
+            byte = result.value();
+            for (u8 i = 0; i < pixel_count; ++i) {
+                if (compression != Compression::RLE4) {
+                    if (!set_byte(byte, true))
+                        return false;
+                } else {
+                    if (!set_byte(byte, i != pixel_count - 1))
+                        return false;
+                    i++;
+                }
+            }
+
+            currently_consuming = RLEState::PixelCount;
+            break;
+        }
+        case RLEState::Meta:
+            if (!streamer.has_u8())
+                return false;
+            byte = streamer.read_u8();
+            if (!byte) {
+                column = 0;
+                row++;
+                currently_consuming = RLEState::PixelCount;
+                continue;
+            }
+            if (byte == 1)
+                return true;
+            if (byte == 2) {
+                u8 offset_x = streamer.read_u8();
+                u8 offset_y = streamer.read_u8();
+                column += offset_x;
+                if (column >= total_columns) {
+                    column -= total_columns;
+                    row++;
+                }
+                row += offset_y;
+                currently_consuming = RLEState::PixelCount;
+                continue;
+            }
+
+            // Consume literal bytes
+            pixel_count = byte;
+            i16 i = byte;
+
+            while (i >= 1) {
+                auto result = read_byte();
+                if (!result.has_value())
+                    return false;
+                byte = result.value();
+                if (!set_byte(byte, i != 1))
+                    return false;
+                i--;
+                if (compression == Compression::RLE4)
+                    i--;
+            }
+
+            // Optionally consume a padding byte
+            if (compression != Compression::RLE4) {
+                if (pixel_count % 2) {
+                    byte = streamer.read_u8();
+                }
+            } else {
+                if (((pixel_count + 1) / 2) % 2) {
+                    byte = streamer.read_u8();
+                }
+            }
+            currently_consuming = RLEState::PixelCount;
+            break;
+        }
+    }
+
+    ASSERT_NOT_REACHED();
+}
+
+static bool decode_bmp_pixel_data(BMPLoadingContext& context)
+{
+    if (context.state == BMPLoadingContext::State::Error)
+        return false;
+
+    if (context.state <= BMPLoadingContext::State::ColorTableDecoded && !decode_bmp_color_table(context))
+        return false;
+
+    const u16 bits_per_pixel = context.dib.core.bpp;
+
+    BitmapFormat format = [&]() -> BitmapFormat {
+        switch (bits_per_pixel) {
+        case 1:
+            return BitmapFormat::Indexed1;
+        case 2:
+            return BitmapFormat::Indexed2;
+        case 4:
+            return BitmapFormat::Indexed4;
+        case 8:
+            return BitmapFormat::Indexed8;
+        case 16:
+            if (context.dib.info.masks.size() == 4)
+                return BitmapFormat::RGBA32;
+            return BitmapFormat::RGB32;
+        case 24:
+            return BitmapFormat::RGB32;
+        case 32:
+            return BitmapFormat::RGBA32;
+        default:
+            return BitmapFormat::Invalid;
+        }
+    }();
+
+    if (format == BitmapFormat::Invalid) {
+        IF_BMP_DEBUG(dbg() << "BMP has invalid bpp of " << bits_per_pixel);
+        context.state = BMPLoadingContext::State::Error;
+        return false;
+    }
+
+    const u32 width = abs(context.dib.core.width);
+    const u32 height = abs(context.dib.core.height);
+    context.bitmap = Bitmap::create_purgeable(format, { static_cast<int>(width), static_cast<int>(height) });
+    if (!context.bitmap) {
+        IF_BMP_DEBUG(dbg() << "BMP appears to have overly large dimensions");
+        return false;
+    }
+
+    auto buffer = ByteBuffer::wrap(context.data + context.data_offset, context.data_size);
+
+    if (context.dib.info.compression == Compression::RLE4 || context.dib.info.compression == Compression::RLE8
+        || context.dib.info.compression == Compression::RLE24) {
+        if (!uncompress_bmp_rle_data(context, buffer))
+            return false;
+    }
+
+    Streamer streamer(buffer.data(), buffer.size());
+
+    auto process_row = [&](u32 row) -> bool {
+        u32 space_remaining_before_consuming_row = streamer.remaining();
+
+        for (u32 column = 0; column < width;) {
+            switch (bits_per_pixel) {
+            case 1: {
+                if (!streamer.has_u8())
+                    return false;
+                u8 byte = streamer.read_u8();
+                u8 mask = 8;
+                while (column < width && mask > 0) {
+                    mask -= 1;
+                    context.bitmap->scanline_u8(row)[column++] = (byte >> mask) & 0x1;
+                }
+                break;
+            }
+            case 2: {
+                if (!streamer.has_u8())
+                    return false;
+                u8 byte = streamer.read_u8();
+                u8 mask = 8;
+                while (column < width && mask > 0) {
+                    mask -= 2;
+                    context.bitmap->scanline_u8(row)[column++] = (byte >> mask) & 0x3;
+                }
+                break;
+            }
+            case 4: {
+                if (!streamer.has_u8())
+                    return false;
+                u8 byte = streamer.read_u8();
+                context.bitmap->scanline_u8(row)[column++] = (byte >> 4) & 0xf;
+                if (column < width)
+                    context.bitmap->scanline_u8(row)[column++] = byte & 0xf;
+                break;
+            }
+            case 8:
+                if (!streamer.has_u8())
+                    return false;
+                context.bitmap->scanline_u8(row)[column++] = streamer.read_u8();
+                break;
+            case 16: {
+                if (!streamer.has_u16())
+                    return false;
+                context.bitmap->scanline(row)[column++] = int_to_scaled_rgb(context, streamer.read_u16());
+                break;
+            }
+            case 24: {
+                if (!streamer.has_u24())
+                    return false;
+                context.bitmap->scanline(row)[column++] = streamer.read_u24();
+                break;
+            }
+            case 32:
+                if (!streamer.has_u32())
+                    return false;
+                if (context.dib.info.masks.is_empty()) {
+                    context.bitmap->scanline(row)[column++] = streamer.read_u32() | 0xff000000;
+                } else {
+                    context.bitmap->scanline(row)[column++] = int_to_scaled_rgb(context, streamer.read_u32());
+                }
+                break;
+            }
+        }
+
+        auto consumed = space_remaining_before_consuming_row - streamer.remaining();
+
+        // Calculate padding
+        u8 bytes_to_drop = [consumed]() -> u8 {
+            switch (consumed % 4) {
+            case 0:
+                return 0;
+            case 1:
+                return 3;
+            case 2:
+                return 2;
+            case 3:
+                return 1;
+            }
+            ASSERT_NOT_REACHED();
+        }();
+        if (streamer.remaining() < bytes_to_drop)
+            return false;
+        streamer.drop_bytes(bytes_to_drop);
+
+        return true;
+    };
+
+    if (context.dib.core.height < 0) {
+        // BMP is stored top-down
+        for (u32 row = 0; row < height; ++row) {
+            if (!process_row(row))
+                return false;
+        }
+    } else {
+        for (i32 row = height - 1; row >= 0; --row) {
+            if (!process_row(row))
+                return false;
+        }
+    }
+
+    for (size_t i = 0; i < context.color_table.size(); ++i)
+        context.bitmap->set_palette_color(i, Color::from_rgb(context.color_table[i]));
+
+    context.state = BMPLoadingContext::State::PixelDataDecoded;
+
+    return true;
+}
+
+static RefPtr<Bitmap> load_bmp_impl(const u8* data, size_t data_size)
+{
+    BMPLoadingContext context;
+    context.data = data;
+    context.data_size = data_size;
+
+    // Forces a decode of the header, dib, and color table as well
+    if (!decode_bmp_pixel_data(context)) {
+        context.state = BMPLoadingContext::State::Error;
+        return nullptr;
+    }
+
+    return context.bitmap;
+}
+
+BMPImageDecoderPlugin::BMPImageDecoderPlugin(const u8* data, size_t data_size)
+{
+    m_context = make<BMPLoadingContext>();
+    m_context->data = data;
+    m_context->data_size = data_size;
+}
+
+BMPImageDecoderPlugin::~BMPImageDecoderPlugin()
+{
+}
+
+IntSize BMPImageDecoderPlugin::size()
+{
+    if (m_context->state == BMPLoadingContext::State::Error)
+        return {};
+
+    if (m_context->state < BMPLoadingContext::State::DIBDecoded && !decode_bmp_dib(*m_context))
+        return {};
+
+    return { m_context->dib.core.width, abs(m_context->dib.core.height) };
+}
+
+RefPtr<Gfx::Bitmap> BMPImageDecoderPlugin::bitmap()
+{
+    if (m_context->state == BMPLoadingContext::State::Error)
+        return nullptr;
+
+    if (m_context->state < BMPLoadingContext::State::PixelDataDecoded && !decode_bmp_pixel_data(*m_context))
+        return nullptr;
+
+    ASSERT(m_context->bitmap);
+    return m_context->bitmap;
+}
+
+void BMPImageDecoderPlugin::set_volatile()
+{
+    if (m_context->bitmap)
+        m_context->bitmap->set_volatile();
+}
+
+bool BMPImageDecoderPlugin::set_nonvolatile()
+{
+    if (!m_context->bitmap)
+        return false;
+    return m_context->bitmap->set_nonvolatile();
+}
+
+bool BMPImageDecoderPlugin::sniff()
+{
+    return decode_bmp_header(*m_context);
+}
+
+bool BMPImageDecoderPlugin::is_animated()
+{
+    return false;
+}
+
+size_t BMPImageDecoderPlugin::loop_count()
+{
+    return 0;
+}
+
+size_t BMPImageDecoderPlugin::frame_count()
+{
+    return 1;
+}
+
+ImageFrameDescriptor BMPImageDecoderPlugin::frame(size_t i)
+{
+    if (i > 0)
+        return { bitmap(), 0 };
+    return {};
+}
+
+}
diff --git a/Libraries/LibGfx/BMPLoader.h b/Libraries/LibGfx/BMPLoader.h
new file mode 100644
index 0000000000..6493b196ea
--- /dev/null
+++ b/Libraries/LibGfx/BMPLoader.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibGfx/Bitmap.h>
+#include <LibGfx/ImageDecoder.h>
+
+namespace Gfx {
+
+RefPtr<Gfx::Bitmap> load_bmp(const StringView& path);
+
+struct BMPLoadingContext;
+
+class BMPImageDecoderPlugin final : public ImageDecoderPlugin {
+public:
+    virtual ~BMPImageDecoderPlugin() override;
+    BMPImageDecoderPlugin(const u8*, size_t);
+
+    virtual IntSize size() override;
+    virtual RefPtr<Gfx::Bitmap> bitmap() override;
+    virtual void set_volatile() override;
+    [[nodiscard]] virtual bool set_nonvolatile() override;
+    virtual bool sniff() override;
+    virtual bool is_animated() override;
+    virtual size_t loop_count() override;
+    virtual size_t frame_count() override;
+    virtual ImageFrameDescriptor frame(size_t i) override;
+
+private:
+    OwnPtr<BMPLoadingContext> m_context;
+};
+
+}
diff --git a/Libraries/LibGfx/Bitmap.cpp b/Libraries/LibGfx/Bitmap.cpp
index c9236e2c96..72f1467ae7 100644
--- a/Libraries/LibGfx/Bitmap.cpp
+++ b/Libraries/LibGfx/Bitmap.cpp
@@ -29,14 +29,13 @@
 #include <AK/SharedBuffer.h>
 #include <AK/String.h>
 #include <LibGfx/Bitmap.h>
+#include <LibGfx/BMPLoader.h>
 #include <LibGfx/GIFLoader.h>
 #include <LibGfx/PNGLoader.h>
 #include <LibGfx/ShareableBitmap.h>
-#include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <sys/mman.h>
-#include <unistd.h>
 
 namespace Gfx {
 
@@ -69,8 +68,7 @@ Bitmap::Bitmap(BitmapFormat format, const IntSize& size, Purgeable purgeable)
 {
     ASSERT(!m_size.is_empty());
     ASSERT(!size_would_overflow(format, size));
-    if (format == BitmapFormat::Indexed8)
-        m_palette = new RGBA32[256];
+    allocate_palette_from_format(format);
     int map_flags = purgeable == Purgeable::Yes ? (MAP_PURGEABLE | MAP_PRIVATE) : (MAP_ANONYMOUS | MAP_PRIVATE);
     m_data = (RGBA32*)mmap_with_name(nullptr, size_in_bytes(), PROT_READ | PROT_WRITE, map_flags, 0, 0, String::format("GraphicsBitmap [%dx%d]", width(), height()).characters());
     ASSERT(m_data && m_data != (void*)-1);
@@ -102,8 +100,7 @@ Bitmap::Bitmap(BitmapFormat format, const IntSize& size, size_t pitch, RGBA32* d
     , m_format(format)
 {
     ASSERT(!size_would_overflow(format, size));
-    if (format == BitmapFormat::Indexed8)
-        m_palette = new RGBA32[256];
+    allocate_palette_from_format(format);
 }
 
 RefPtr<Bitmap> Bitmap::create_with_shared_buffer(BitmapFormat format, NonnullRefPtr<SharedBuffer>&& shared_buffer, const IntSize& size)
@@ -120,7 +117,7 @@ Bitmap::Bitmap(BitmapFormat format, NonnullRefPtr<SharedBuffer>&& shared_buffer,
     , m_format(format)
     , m_shared_buffer(move(shared_buffer))
 {
-    ASSERT(format != BitmapFormat::Indexed8);
+    ASSERT(!is_indexed(format));
     ASSERT(!size_would_overflow(format, size));
 }
 
@@ -200,7 +197,7 @@ void Bitmap::set_mmap_name(const StringView& name)
 
 void Bitmap::fill(Color color)
 {
-    ASSERT(m_format == BitmapFormat::RGB32 || m_format == BitmapFormat::RGBA32);
+    ASSERT(!is_indexed(m_format));
     for (int y = 0; y < height(); ++y) {
         auto* scanline = this->scanline(y);
         fast_u32_fill(scanline, color.value(), width());
@@ -249,4 +246,17 @@ ShareableBitmap Bitmap::to_shareable_bitmap(pid_t peer_pid) const
     return ShareableBitmap(*bitmap);
 }
 
+void Bitmap::allocate_palette_from_format(BitmapFormat format)
+{
+    if (format == BitmapFormat::Indexed1) {
+        m_palette = new RGBA32[2];
+    } else if (format == BitmapFormat::Indexed2) {
+        m_palette = new RGBA32[4];
+    } else if (format == BitmapFormat::Indexed4) {
+        m_palette = new RGBA32[16];
+    } else if (format == BitmapFormat::Indexed8) {
+        m_palette = new RGBA32[256];
+    }
+}
+
 }
diff --git a/Libraries/LibGfx/Bitmap.h b/Libraries/LibGfx/Bitmap.h
index 4e313a402a..85304f39bb 100644
--- a/Libraries/LibGfx/Bitmap.h
+++ b/Libraries/LibGfx/Bitmap.h
@@ -35,15 +35,19 @@
 
 #define ENUMERATE_IMAGE_FORMATS           \
     __ENUMERATE_IMAGE_FORMAT(png, ".png") \
-    __ENUMERATE_IMAGE_FORMAT(gif, ".gif")
+    __ENUMERATE_IMAGE_FORMAT(gif, ".gif") \
+    __ENUMERATE_IMAGE_FORMAT(bmp, ".bmp")
 
 namespace Gfx {
 
 enum class BitmapFormat {
     Invalid,
+    Indexed1,
+    Indexed2,
+    Indexed4,
+    Indexed8,
     RGB32,
     RGBA32,
-    Indexed8
 };
 
 enum RotationDirection {
@@ -77,6 +81,8 @@ public:
 
     ~Bitmap();
 
+    u8* scanline_u8(int y);
+    const u8* scanline_u8(int y) const;
     RGBA32* scanline(int y);
     const RGBA32* scanline(int y) const;
 
@@ -93,9 +99,21 @@ public:
     SharedBuffer* shared_buffer() { return m_shared_buffer.ptr(); }
     const SharedBuffer* shared_buffer() const { return m_shared_buffer.ptr(); }
 
+    ALWAYS_INLINE static bool is_indexed(BitmapFormat format)
+    {
+        return format == BitmapFormat::Indexed8 || format == BitmapFormat::Indexed4
+            || format == BitmapFormat::Indexed2 || format == BitmapFormat::Indexed1;
+    }
+
     static unsigned bpp_for_format(BitmapFormat format)
     {
         switch (format) {
+        case BitmapFormat::Indexed1:
+            return 1;
+        case BitmapFormat::Indexed2:
+            return 2;
+        case BitmapFormat::Indexed4:
+            return 4;
         case BitmapFormat::Indexed8:
             return 8;
         case BitmapFormat::RGB32:
@@ -167,6 +185,8 @@ private:
     Bitmap(BitmapFormat, const IntSize&, size_t pitch, RGBA32*);
     Bitmap(BitmapFormat, NonnullRefPtr<SharedBuffer>&&, const IntSize&);
 
+    void allocate_palette_from_format(BitmapFormat);
+
     IntSize m_size;
     RGBA32* m_data { nullptr };
     RGBA32* m_palette { nullptr };
@@ -178,14 +198,24 @@ private:
     RefPtr<SharedBuffer> m_shared_buffer;
 };
 
+inline u8* Bitmap::scanline_u8(int y)
+{
+    return (u8*)m_data + (y * m_pitch);
+}
+
+inline const u8* Bitmap::scanline_u8(int y) const
+{
+    return (const u8*)m_data + (y * m_pitch);
+}
+
 inline RGBA32* Bitmap::scanline(int y)
 {
-    return reinterpret_cast<RGBA32*>((((u8*)m_data) + (y * m_pitch)));
+    return reinterpret_cast<RGBA32*>(scanline_u8(y));
 }
 
 inline const RGBA32* Bitmap::scanline(int y) const
 {
-    return reinterpret_cast<const RGBA32*>((((const u8*)m_data) + (y * m_pitch)));
+    return reinterpret_cast<const RGBA32*>(scanline_u8(y));
 }
 
 inline const u8* Bitmap::bits(int y) const
@@ -211,9 +241,27 @@ inline Color Bitmap::get_pixel<BitmapFormat::RGBA32>(int x, int y) const
 }
 
 template<>
+inline Color Bitmap::get_pixel<BitmapFormat::Indexed1>(int x, int y) const
+{
+    return Color::from_rgb(m_palette[bits(y)[x]]);
+}
+
+template<>
+inline Color Bitmap::get_pixel<BitmapFormat::Indexed2>(int x, int y) const
+{
+    return Color::from_rgb(m_palette[bits(y)[x]]);
+}
+
+template<>
+inline Color Bitmap::get_pixel<BitmapFormat::Indexed4>(int x, int y) const
+{
+    return Color::from_rgb(m_palette[bits(y)[x]]);
+}
+
+template<>
 inline Color Bitmap::get_pixel<BitmapFormat::Indexed8>(int x, int y) const
 {
-    return Color::from_rgba(m_palette[bits(y)[x]]);
+    return Color::from_rgb(m_palette[bits(y)[x]]);
 }
 
 inline Color Bitmap::get_pixel(int x, int y) const
@@ -223,11 +271,16 @@ inline Color Bitmap::get_pixel(int x, int y) const
         return get_pixel<BitmapFormat::RGB32>(x, y);
     case BitmapFormat::RGBA32:
         return get_pixel<BitmapFormat::RGBA32>(x, y);
+    case BitmapFormat::Indexed1:
+        return get_pixel<BitmapFormat::Indexed1>(x, y);
+    case BitmapFormat::Indexed2:
+        return get_pixel<BitmapFormat::Indexed2>(x, y);
+    case BitmapFormat::Indexed4:
+        return get_pixel<BitmapFormat::Indexed4>(x, y);
     case BitmapFormat::Indexed8:
         return get_pixel<BitmapFormat::Indexed8>(x, y);
     default:
         ASSERT_NOT_REACHED();
-        return {};
     }
 }
 
@@ -252,6 +305,9 @@ inline void Bitmap::set_pixel(int x, int y, Color color)
     case BitmapFormat::RGBA32:
         set_pixel<BitmapFormat::RGBA32>(x, y, color);
         break;
+    case BitmapFormat::Indexed1:
+    case BitmapFormat::Indexed2:
+    case BitmapFormat::Indexed4:
     case BitmapFormat::Indexed8:
         ASSERT_NOT_REACHED();
     default:
diff --git a/Libraries/LibGfx/CMakeLists.txt b/Libraries/LibGfx/CMakeLists.txt
index 3ab00d506c..d81bfffb81 100644
--- a/Libraries/LibGfx/CMakeLists.txt
+++ b/Libraries/LibGfx/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(SOURCES
     AffineTransform.cpp
     Bitmap.cpp
+    BMPLoader.cpp
     CharacterBitmap.cpp
     Color.cpp
     DisjointRectSet.cpp
diff --git a/Libraries/LibGfx/ImageDecoder.cpp b/Libraries/LibGfx/ImageDecoder.cpp
index 558656cabb..31c6408152 100644
--- a/Libraries/LibGfx/ImageDecoder.cpp
+++ b/Libraries/LibGfx/ImageDecoder.cpp
@@ -25,6 +25,7 @@
  */
 
 #include <LibGfx/ImageDecoder.h>
+#include <LibGfx/BMPLoader.h>
 #include <LibGfx/GIFLoader.h>
 #include <LibGfx/PNGLoader.h>
 
@@ -40,6 +41,10 @@ ImageDecoder::ImageDecoder(const u8* data, size_t size)
     if (m_plugin->sniff())
         return;
 
+    m_plugin = make<BMPImageDecoderPlugin>(data, size);
+    if (m_plugin->sniff())
+        return;
+
     m_plugin = nullptr;
 }
 
diff --git a/Libraries/LibGfx/Painter.cpp b/Libraries/LibGfx/Painter.cpp
index 8288d7377e..3d1fa05ab5 100644
--- a/Libraries/LibGfx/Painter.cpp
+++ b/Libraries/LibGfx/Painter.cpp
@@ -53,6 +53,12 @@ ALWAYS_INLINE Color get_pixel(const Gfx::Bitmap& bitmap, int x, int y)
 {
     if constexpr (format == BitmapFormat::Indexed8)
         return bitmap.palette_color(bitmap.bits(y)[x]);
+    if constexpr (format == BitmapFormat::Indexed4)
+        return bitmap.palette_color(bitmap.bits(y)[x]);
+    if constexpr (format == BitmapFormat::Indexed2)
+        return bitmap.palette_color(bitmap.bits(y)[x]);
+    if constexpr (format == BitmapFormat::Indexed1)
+        return bitmap.palette_color(bitmap.bits(y)[x]);
     if constexpr (format == BitmapFormat::RGB32)
         return Color::from_rgb(bitmap.scanline(y)[x]);
     if constexpr (format == BitmapFormat::RGBA32)
@@ -668,7 +674,7 @@ void Painter::blit(const IntPoint& position, const Gfx::Bitmap& source, const In
         return;
     }
 
-    if (source.format() == BitmapFormat::Indexed8) {
+    if (Bitmap::is_indexed(source.format())) {
         const u8* src = source.bits(src_rect.top() + first_row) + src_rect.left() + first_column;
         const size_t src_skip = source.pitch();
         for (int row = first_row; row <= last_row; ++row) {
@@ -761,6 +767,15 @@ void Painter::draw_scaled_bitmap(const IntRect& a_dst_rect, const Gfx::Bitmap& s
         case BitmapFormat::Indexed8:
             do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, hscale, vscale, get_pixel<BitmapFormat::Indexed8>);
             break;
+        case BitmapFormat::Indexed4:
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, hscale, vscale, get_pixel<BitmapFormat::Indexed4>);
+            break;
+        case BitmapFormat::Indexed2:
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, hscale, vscale, get_pixel<BitmapFormat::Indexed2>);
+            break;
+        case BitmapFormat::Indexed1:
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, hscale, vscale, get_pixel<BitmapFormat::Indexed1>);
+            break;
         default:
             do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, hscale, vscale, get_pixel<BitmapFormat::Invalid>);
             break;
diff --git a/Libraries/LibWeb/Loader/Resource.cpp b/Libraries/LibWeb/Loader/Resource.cpp
index f4fe30ce4a..48eb443991 100644
--- a/Libraries/LibWeb/Loader/Resource.cpp
+++ b/Libraries/LibWeb/Loader/Resource.cpp
@@ -83,6 +83,8 @@ static String guess_mime_type_based_on_filename(const URL& url)
         return "image/png";
     if (url.path().ends_with(".gif"))
         return "image/gif";
+    if (url.path().ends_with(".bmp"))
+        return "image/bmp";
     if (url.path().ends_with(".md"))
         return "text/markdown";
     if (url.path().ends_with(".html") || url.path().ends_with(".htm"))