64 lines
1.9 KiB
C++
64 lines
1.9 KiB
C++
// Copyright (c) the JPEG XL Project Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "lib/extras/alpha_blend.h"
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#include "lib/extras/packed_image.h"
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namespace jxl {
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namespace extras {
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namespace {
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void AlphaBlend(PackedFrame* frame, const float background[3]) {
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if (!frame) return;
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const PackedImage& im = frame->color;
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JxlPixelFormat format = im.format;
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if (format.num_channels != 2 && format.num_channels != 4) {
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return;
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}
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--format.num_channels;
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JXL_ASSIGN_OR_DIE(PackedImage blended,
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PackedImage::Create(im.xsize, im.ysize, format));
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// TODO(szabadka) SIMDify this and make it work for float16.
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for (size_t y = 0; y < im.ysize; ++y) {
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for (size_t x = 0; x < im.xsize; ++x) {
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if (format.num_channels == 2) {
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float g = im.GetPixelValue(y, x, 0);
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float a = im.GetPixelValue(y, x, 1);
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float out = g * a + background[0] * (1 - a);
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blended.SetPixelValue(y, x, 0, out);
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} else {
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float r = im.GetPixelValue(y, x, 0);
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float g = im.GetPixelValue(y, x, 1);
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float b = im.GetPixelValue(y, x, 2);
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float a = im.GetPixelValue(y, x, 3);
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float out_r = r * a + background[0] * (1 - a);
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float out_g = g * a + background[1] * (1 - a);
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float out_b = b * a + background[2] * (1 - a);
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blended.SetPixelValue(y, x, 0, out_r);
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blended.SetPixelValue(y, x, 1, out_g);
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blended.SetPixelValue(y, x, 2, out_b);
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}
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}
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}
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frame->color = blended.Copy();
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}
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} // namespace
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void AlphaBlend(PackedPixelFile* ppf, const float background[3]) {
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if (!ppf || ppf->info.alpha_bits == 0) {
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return;
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}
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ppf->info.alpha_bits = 0;
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AlphaBlend(ppf->preview_frame.get(), background);
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for (auto& frame : ppf->frames) {
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AlphaBlend(&frame, background);
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}
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}
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} // namespace extras
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} // namespace jxl
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