// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "lib/jxl/enc_comparator.h"
#include <jxl/memory_manager.h>
#include <algorithm>
#include <cstddef>
#include "lib/jxl/base/compiler_specific.h"
#include "lib/jxl/base/status.h"
#include "lib/jxl/enc_gamma_correct.h"
#include "lib/jxl/enc_image_bundle.h"
namespace jxl {
namespace {
// color is linear, but blending happens in gamma-compressed space using
// (gamma-compressed) grayscale background color, alpha image represents
// weights of the sRGB colors in the [0 .. (1 << bit_depth) - 1] interval,
// output image is in linear space.
void AlphaBlend(
const Image3F& in,
const size_t c,
float background_linear,
const ImageF& alpha, Image3F* out) {
const float background = LinearToSrgb8Direct(background_linear);
for (size_t y = 0; y < out->ysize(); ++y) {
const float* JXL_RESTRICT row_a = alpha.ConstRow(y);
const float* JXL_RESTRICT row_i = in.ConstPlaneRow(c, y);
float* JXL_RESTRICT row_o = out->PlaneRow(c, y);
for (size_t x = 0; x < out->xsize(); ++x) {
const float a = row_a[x];
if (a <= 0.f) {
row_o[x] = background_linear;
}
else if (a >= 1.f) {
row_o[x] = row_i[x];
}
else {
const float w_fg = a;
const float w_bg = 1.0f - w_fg;
const float fg = w_fg * LinearToSrgb8Direct(row_i[x]);
const float bg = w_bg * background;
row_o[x] = Srgb8ToLinearDirect(fg + bg);
}
}
}
}
void AlphaBlend(
float background_linear, ImageBundle* io_linear_srgb) {
// No alpha => all opaque.
if (!io_linear_srgb->HasAlpha())
return;
for (size_t c = 0; c < 3; ++c) {
AlphaBlend(*io_linear_srgb->color(), c, background_linear,
*io_linear_srgb->alpha(), io_linear_srgb->color());
}
}
Status ComputeScoreImpl(
const ImageBundle& rgb0,
const ImageBundle& rgb1,
Comparator* comparator, ImageF* distmap,
float& score) {
JXL_RETURN_IF_ERROR(comparator->SetReferenceImage(rgb0));
JXL_RETURN_IF_ERROR(comparator->CompareWith(rgb1, distmap, &score));
return true;
}
}
// namespace
Status ComputeScore(
const ImageBundle& rgb0,
const ImageBundle& rgb1,
Comparator* comparator,
const JxlCmsInterface& cms,
float* score, ImageF* diffmap, ThreadPool* pool,
bool ignore_alpha) {
JxlMemoryManager* memory_manager = rgb0.memory_manager();
// Convert to linear sRGB (unless already in that space)
ImageMetadata metadata0 = *rgb0.metadata();
ImageBundle store0(memory_manager, &metadata0);
const ImageBundle* linear_srgb0;
JXL_RETURN_IF_ERROR(
TransformIfNeeded(rgb0, ColorEncoding::LinearSRGB(rgb0.IsGray()), cms,
pool, &store0, &linear_srgb0));
ImageMetadata metadata1 = *rgb1.metadata();
ImageBundle store1(memory_manager, &metadata1);
const ImageBundle* linear_srgb1;
JXL_RETURN_IF_ERROR(
TransformIfNeeded(rgb1, ColorEncoding::LinearSRGB(rgb1.IsGray()), cms,
pool, &store1, &linear_srgb1));
// No alpha: skip blending, only need a single call to Butteraugli.
if (ignore_alpha || (!rgb0.HasAlpha() && !rgb1.HasAlpha())) {
JXL_RETURN_IF_ERROR(ComputeScoreImpl(*linear_srgb0, *linear_srgb1,
comparator, diffmap, *score));
return true;
}
// Blend on black and white backgrounds
const float black = 0.0f;
JXL_ASSIGN_OR_RETURN(ImageBundle blended_black0, linear_srgb0->Copy());
JXL_ASSIGN_OR_RETURN(ImageBundle blended_black1, linear_srgb1->Copy());
AlphaBlend(black, &blended_black0);
AlphaBlend(black, &blended_black1);
const float white = 1.0f;
JXL_ASSIGN_OR_RETURN(ImageBundle blended_white0, linear_srgb0->Copy());
JXL_ASSIGN_OR_RETURN(ImageBundle blended_white1, linear_srgb1->Copy());
AlphaBlend(white, &blended_white0);
AlphaBlend(white, &blended_white1);
ImageF diffmap_black;
ImageF diffmap_white;
float dist_black;
JXL_RETURN_IF_ERROR(ComputeScoreImpl(blended_black0, blended_black1,
comparator, &diffmap_black, dist_black));
float dist_white;
JXL_RETURN_IF_ERROR(ComputeScoreImpl(blended_white0, blended_white1,
comparator, &diffmap_white, dist_white));
// diffmap and return values are the max of diffmap_black/white.
if (diffmap != nullptr) {
const size_t xsize = rgb0.xsize();
const size_t ysize = rgb0.ysize();
JXL_ASSIGN_OR_RETURN(*diffmap,
ImageF::Create(memory_manager, xsize, ysize));
for (size_t y = 0; y < ysize; ++y) {
const float* JXL_RESTRICT row_black = diffmap_black.ConstRow(y);
const float* JXL_RESTRICT row_white = diffmap_white.ConstRow(y);
float* JXL_RESTRICT row_out = diffmap->Row(y);
for (size_t x = 0; x < xsize; ++x) {
row_out[x] = std::max(row_black[x], row_white[x]);
}
}
}
*score = std::max(dist_black, dist_white);
return true;
}
}
// namespace jxl
