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/*
* Copyright (c) 2021, Pierre Hoffmeister
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/String.h>
#include <LibCrypto/Checksum/CRC32.h>
#include <LibGfx/Bitmap.h>
#include <LibGfx/PNGWriter.h>
namespace Gfx {
class PNGChunk {
public:
explicit PNGChunk(String);
Vector<u8> const& data() const { return m_data; };
String const& type() const { return m_type; };
void add_u8(u8);
void add_u16_big(u16);
void add_u32_big(u32);
void add_u16_little(u16);
void add_u32_little(u32);
private:
Vector<u8> m_data;
String m_type;
};
class NonCompressibleBlock {
public:
void finalize(PNGChunk&);
void add_byte_to_block(u8 data, PNGChunk&);
u32 adler_s1() const { return m_adler_s1; }
u32 adler_s2() const { return m_adler_s2; }
private:
void add_block_to_chunk(PNGChunk&, bool);
void update_adler(u8);
bool full() { return m_non_compressible_data.size() == 65535; }
Vector<u8> m_non_compressible_data;
u32 m_adler_s1 { 1 };
u32 m_adler_s2 { 0 };
};
PNGChunk::PNGChunk(String type)
: m_type(move(type))
{
}
void PNGChunk::add_u8(u8 data)
{
m_data.append(data);
}
void PNGChunk::add_u16_little(u16 data)
{
m_data.append(data & 0xff);
m_data.append((data >> 8) & 0xff);
}
void PNGChunk::add_u32_little(u32 data)
{
m_data.append(data & 0xff);
m_data.append((data >> 8) & 0xff);
m_data.append((data >> 16) & 0xff);
m_data.append((data >> 24) & 0xff);
}
void PNGChunk::add_u32_big(u32 data)
{
m_data.append((data >> 24) & 0xff);
m_data.append((data >> 16) & 0xff);
m_data.append((data >> 8) & 0xff);
m_data.append(data & 0xff);
}
void PNGChunk::add_u16_big(u16 data)
{
m_data.append((data >> 8) & 0xff);
m_data.append(data & 0xff);
}
void NonCompressibleBlock::add_byte_to_block(u8 data, PNGChunk& chunk)
{
m_non_compressible_data.append(data);
update_adler(data);
if (full()) {
add_block_to_chunk(chunk, false);
m_non_compressible_data.clear();
}
}
void NonCompressibleBlock::add_block_to_chunk(PNGChunk& png_chunk, bool last)
{
if (last) {
png_chunk.add_u8(1);
} else {
png_chunk.add_u8(0);
}
auto len = m_non_compressible_data.size();
auto nlen = ~len;
png_chunk.add_u16_little(len);
png_chunk.add_u16_little(nlen);
for (auto non_compressed_byte : m_non_compressible_data) {
png_chunk.add_u8(non_compressed_byte);
}
}
void NonCompressibleBlock::finalize(PNGChunk& chunk)
{
add_block_to_chunk(chunk, true);
}
void NonCompressibleBlock::update_adler(u8 data)
{
m_adler_s1 = (m_adler_s1 + data) % 65521;
m_adler_s2 = (m_adler_s2 + m_adler_s1) % 65521;
}
void PNGWriter::add_chunk(PNGChunk const& png_chunk)
{
Vector<u8> combined;
for (auto character : png_chunk.type()) {
combined.append(character);
}
combined.append(png_chunk.data());
auto crc = BigEndian(Crypto::Checksum::CRC32({ (const u8*)combined.data(), combined.size() }).digest());
auto data_len = BigEndian(png_chunk.data().size());
ByteBuffer buf;
buf.append(&data_len, sizeof(u32));
buf.append(combined.data(), combined.size());
buf.append(&crc, sizeof(u32));
m_data.append(buf.data(), buf.size());
}
void PNGWriter::add_png_header()
{
const u8 png_header[8] = { 0x89, 'P', 'N', 'G', 13, 10, 26, 10 };
m_data.append(png_header, sizeof(png_header));
}
void PNGWriter::add_IHDR_chunk(u32 width, u32 height, u8 bit_depth, u8 color_type, u8 compression_method, u8 filter_method, u8 interlace_method)
{
PNGChunk png_chunk { "IHDR" };
png_chunk.add_u32_big(width);
png_chunk.add_u32_big(height);
png_chunk.add_u8(bit_depth);
png_chunk.add_u8(color_type);
png_chunk.add_u8(compression_method);
png_chunk.add_u8(filter_method);
png_chunk.add_u8(interlace_method);
add_chunk(png_chunk);
}
void PNGWriter::add_IEND_chunk()
{
PNGChunk png_chunk { "IEND" };
add_chunk(png_chunk);
}
void PNGWriter::add_IDAT_chunk(Gfx::Bitmap const& bitmap)
{
PNGChunk png_chunk { "IDAT" };
u16 CMF_FLG = 0x81d;
png_chunk.add_u16_big(CMF_FLG);
NonCompressibleBlock non_compressible_block;
for (int y = 0; y < bitmap.height(); ++y) {
non_compressible_block.add_byte_to_block(0, png_chunk);
for (int x = 0; x < bitmap.width(); ++x) {
auto pixel = bitmap.get_pixel(x, y);
non_compressible_block.add_byte_to_block(pixel.red(), png_chunk);
non_compressible_block.add_byte_to_block(pixel.green(), png_chunk);
non_compressible_block.add_byte_to_block(pixel.blue(), png_chunk);
non_compressible_block.add_byte_to_block(pixel.alpha(), png_chunk);
}
}
non_compressible_block.finalize(png_chunk);
png_chunk.add_u16_big(non_compressible_block.adler_s2());
png_chunk.add_u16_big(non_compressible_block.adler_s1());
add_chunk(png_chunk);
}
ByteBuffer PNGWriter::encode(Gfx::Bitmap const& bitmap)
{
PNGWriter writer;
writer.add_png_header();
writer.add_IHDR_chunk(bitmap.width(), bitmap.height(), 8, 6, 0, 0, 0);
writer.add_IDAT_chunk(bitmap);
writer.add_IEND_chunk();
return ByteBuffer::copy(writer.m_data);
}
}
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