LibGfx: Add scaling methods to Bitmap

2 files changed, 111 insertions, 0 deletions

diff --git a/Userland/Libraries/LibGfx/Bitmap.cpp b/Userland/Libraries/LibGfx/Bitmap.cpp
index 201e334a0b..b3be385944 100644
--- a/Userland/Libraries/LibGfx/Bitmap.cpp
+++ b/Userland/Libraries/LibGfx/Bitmap.cpp
@@ -389,6 +389,115 @@ RefPtr<Gfx::Bitmap> Bitmap::flipped(Gfx::Orientation orientation) const
     return new_bitmap;
 }
 
+RefPtr<Gfx::Bitmap> Bitmap::scaled(int sx, int sy) const
+{
+    VERIFY(sx >= 0 && sy >= 0);
+    if (sx == 1 && sy == 1)
+        return this;
+
+    auto new_bitmap = Gfx::Bitmap::create(format(), { width() * sx, height() * sy }, scale());
+    if (!new_bitmap)
+        return nullptr;
+
+    auto old_width = physical_width();
+    auto old_height = physical_height();
+
+    for (int y = 0; y < old_height; y++) {
+        for (int x = 0; x < old_width; x++) {
+            auto color = get_pixel(x, y);
+
+            auto base_x = x * sx;
+            auto base_y = y * sy;
+            for (int new_y = base_y; new_y < base_y + sy; new_y++) {
+                for (int new_x = base_x; new_x < base_x + sx; new_x++) {
+                    new_bitmap->set_pixel(new_x, new_y, color);
+                }
+            }
+        }
+    }
+
+    return new_bitmap;
+}
+
+// http://fourier.eng.hmc.edu/e161/lectures/resize/node3.html
+RefPtr<Gfx::Bitmap> Bitmap::scaled(float sx, float sy) const
+{
+    VERIFY(sx >= 0.0f && sy >= 0.0f);
+    if (floorf(sx) == sx && floorf(sy) == sy)
+        return scaled(static_cast<int>(sx), static_cast<int>(sy));
+
+    auto new_bitmap = Gfx::Bitmap::create(format(), { width() * sx, height() * sy }, scale());
+    if (!new_bitmap)
+        return nullptr;
+
+    auto old_width = physical_width();
+    auto old_height = physical_height();
+    auto new_width = new_bitmap->physical_width();
+    auto new_height = new_bitmap->physical_height();
+
+    // The interpolation goes out of bounds on the bottom- and right-most edges.
+    // We handle those in two specialized loops not only to make them faster, but
+    // also to avoid four branch checks for every pixel.
+
+    for (int y = 0; y < new_height - 1; y++) {
+        for (int x = 0; x < new_width - 1; x++) {
+            auto p = static_cast<float>(x) * static_cast<float>(old_width - 1) / static_cast<float>(new_width - 1);
+            auto q = static_cast<float>(y) * static_cast<float>(old_height - 1) / static_cast<float>(new_height - 1);
+
+            int i = floor(p);
+            int j = floor(q);
+            float u = p - static_cast<float>(i);
+            float v = q - static_cast<float>(j);
+
+            auto a = get_pixel(i, j);
+            auto b = get_pixel(i + 1, j);
+            auto c = get_pixel(i, j + 1);
+            auto d = get_pixel(i + 1, j + 1);
+
+            auto e = a.interpolate(b, u);
+            auto f = c.interpolate(d, u);
+            auto color = e.interpolate(f, v);
+            new_bitmap->set_pixel(x, y, color);
+        }
+    }
+
+    // Bottom strip (excluding last pixel)
+    auto old_bottom_y = old_height - 1;
+    auto new_bottom_y = new_height - 1;
+    for (int x = 0; x < new_width - 1; x++) {
+        auto p = static_cast<float>(x) * static_cast<float>(old_width - 1) / static_cast<float>(new_width - 1);
+
+        int i = floor(p);
+        float u = p - static_cast<float>(i);
+
+        auto a = get_pixel(i, old_bottom_y);
+        auto b = get_pixel(i + 1, old_bottom_y);
+        auto color = a.interpolate(b, u);
+        new_bitmap->set_pixel(x, new_bottom_y, color);
+    }
+
+    // Right strip (excluding last pixel)
+    auto old_right_x = old_width - 1;
+    auto new_right_x = new_width - 1;
+    for (int y = 0; y < new_height - 1; y++) {
+        auto q = static_cast<float>(y) * static_cast<float>(old_height - 1) / static_cast<float>(new_height - 1);
+
+        int j = floor(q);
+        float v = q - static_cast<float>(j);
+
+        auto c = get_pixel(old_right_x, j);
+        auto d = get_pixel(old_right_x, j + 1);
+
+        auto color = c.interpolate(d, v);
+        new_bitmap->set_pixel(new_right_x, y, color);
+    }
+
+    // Bottom-right pixel
+    new_bitmap->set_pixel(new_width - 1, new_height - 1, get_pixel(physical_width() - 1, physical_height() - 1));
+
+    return new_bitmap;
+}
+
 #ifdef __serenity__
 RefPtr<Bitmap> Bitmap::to_bitmap_backed_by_anon_fd() const
 {
diff --git a/Userland/Libraries/LibGfx/Bitmap.h b/Userland/Libraries/LibGfx/Bitmap.h
index 572a526cc2..be920a64ee 100644
--- a/Userland/Libraries/LibGfx/Bitmap.h
+++ b/Userland/Libraries/LibGfx/Bitmap.h
@@ -115,6 +115,8 @@ public:
 
     RefPtr<Gfx::Bitmap> rotated(Gfx::RotationDirection) const;
     RefPtr<Gfx::Bitmap> flipped(Gfx::Orientation) const;
+    RefPtr<Gfx::Bitmap> scaled(int sx, int sy) const;
+    RefPtr<Gfx::Bitmap> scaled(float sx, float sy) const;
     RefPtr<Bitmap> to_bitmap_backed_by_anon_fd() const;
     ByteBuffer serialize_to_byte_buffer() const;