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LibGfx: Extract free add_argb32() function in webp decoder

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Nico Weber 2023-04-06 21:02:24 -04:00 • committed by Linus Groh
parent 50c9b51eca
commit 6f4fdd85b7
1 changed files with 15 additions and 16 deletions
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31
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -728,6 +728,17 @@ static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8L_image(WebPLoadingCo
namespace {
static ARGB32 add_argb32(ARGB32 a, ARGB32 b)
{
auto a_color = Color::from_argb(a);
auto b_color = Color::from_argb(b);
return Color(a_color.red() + b_color.red(),
a_color.green() + b_color.green(),
a_color.blue() + b_color.blue(),
a_color.alpha() + b_color.alpha())
.value();
}
class Transform {
public:
virtual ~Transform();
@ -818,7 +829,6 @@ private:
}
static ErrorOr<ARGB32> predict(u8 predictor, ARGB32 TL, ARGB32 T, ARGB32 TR, ARGB32 L);
static ARGB32 inverse_transform(ARGB32 pixel, ARGB32 prediction);
int m_size_bits;
NonnullRefPtr<Bitmap> m_predictor_bitmap;
@ -842,15 +852,15 @@ ErrorOr<void> PredictorTransform::transform(Bitmap& bitmap)
// "There are special handling rules for some border pixels.
// If there is a prediction transform, regardless of the mode [0..13] for these pixels,
// the predicted value for the left-topmost pixel of the image is 0xff000000,
bitmap.scanline(0)[0] = inverse_transform(bitmap.scanline(0)[0], 0xff000000);
bitmap.scanline(0)[0] = add_argb32(bitmap.scanline(0)[0], 0xff000000);
// L-pixel for all pixels on the top row,
for (int x = 1; x < bitmap.width(); ++x)
bitmap.scanline(0)[x] = inverse_transform(bitmap.scanline(0)[x], bitmap.scanline(0)[x - 1]);
bitmap.scanline(0)[x] = add_argb32(bitmap.scanline(0)[x], bitmap.scanline(0)[x - 1]);
// and T-pixel for all pixels on the leftmost column."
for (int y = 1; y < bitmap.height(); ++y)
bitmap.scanline(y)[0] = inverse_transform(bitmap.scanline(y)[0], bitmap.scanline(y - 1)[0]);
bitmap.scanline(y)[0] = add_argb32(bitmap.scanline(y)[0], bitmap.scanline(y - 1)[0]);
ARGB32* bitmap_previous_scanline = bitmap.scanline(0);
for (int y = 1; y < bitmap.height(); ++y) {
@ -873,7 +883,7 @@ ErrorOr<void> PredictorTransform::transform(Bitmap& bitmap)
u8 predictor = Color::from_argb(predictor_scanline[predictor_x]).green();
ARGB32 predicted = TRY(predict(predictor, TL, T, TR, L));
bitmap_scanline[x] = inverse_transform(bitmap_scanline[x], predicted);
bitmap_scanline[x] = add_argb32(bitmap_scanline[x], predicted);
TL = T;
T = TR;
@ -956,17 +966,6 @@ ErrorOr<ARGB32> PredictorTransform::predict(u8 predictor, ARGB32 TL, ARGB32 T, A
return Error::from_string_literal("WebPImageDecoderPlugin: invalid predictor");
}
ARGB32 PredictorTransform::inverse_transform(ARGB32 pixel, ARGB32 prediction)
{
auto pixel_color = Color::from_argb(pixel);
auto prediction_color = Color::from_argb(prediction);
return Color(pixel_color.red() + prediction_color.red(),
pixel_color.green() + prediction_color.green(),
pixel_color.blue() + prediction_color.blue(),
pixel_color.alpha() + prediction_color.alpha())
.value();
}
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#42_color_transform
class ColorTransform : public Transform {
public: