image_operations_unittest.cc | Explore in Territory

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

#include "skia/ext/image_operations.h"

#include <stddef.h>
#include <stdint.h>

#include <algorithm>
#include <cmath>
#include <iomanip>
#include <numbers>
#include <vector>

#include "base/compiler_specific.h"
#include "base/files/file_util.h"
#include "base/strings/string_util.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkColorSpace.h"
#include "third_party/skia/include/core/SkImageInfo.h"
#include "third_party/skia/include/core/SkRect.h"
#include "ui/gfx/codec/png_codec.h"
#include "ui/gfx/geometry/size.h"

namespace {

// Computes the average pixel value for the given range, inclusive.
uint32_t AveragePixel(const SkBitmap& bmp,
                      int x_min, int x_max,
                      int y_min, int y_max) { … }

// Computes the average pixel (/color) value for the given colors.
SkColor AveragePixel(const SkColor colors[], size_t color_count) { … }

void PrintPixel(const SkBitmap& bmp,
                int x_min, int x_max,
                int y_min, int y_max) { … }

// Returns the euclidian distance between two RGBA colors interpreted
// as 4-components vectors.
//
// Notes:
// - This is a really poor definition of color distance. Yet it
//   is "good enough" for our uses here.
// - More realistic measures like the various Delta E formulas defined
//   by CIE are way more complex and themselves require the RGBA to
//   to transformed into CIELAB (typically via sRGB first).
// - The static_cast<int> below are needed to avoid interpreting "negative"
//   differences as huge positive values.
float ColorsEuclidianDistance(const SkColor a, const SkColor b) { … }

// Returns true if each channel of the given two colors are "close." This is
// used for comparing colors where rounding errors may cause off-by-one.
bool ColorsClose(uint32_t a, uint32_t b) { … }

void FillDataToBitmap(int w, int h, SkBitmap* bmp) { … }

// Draws a checkerboard pattern into the w x h bitmap passed in.
// Each rectangle is rect_w in width, rect_h in height.
// The colors alternate between color1 and color2, color1 being used
// in the rectangle at the top left corner.
void DrawCheckerToBitmap(int w, int h,
                         SkColor color1, SkColor color2,
                         int rect_w, int rect_h,
                         SkBitmap* bmp) { … }

// DEBUG_BITMAP_GENERATION (0 or 1) controls whether the routines
// to save the test bitmaps are present. By default the test just fails
// without reading/writing files but it is then convenient to have
// a simple way to make the failing tests write out the input/output images
// to check them visually.
#define DEBUG_BITMAP_GENERATION …

#if DEBUG_BITMAP_GENERATION
void SaveBitmapToPNG(const SkBitmap& bmp, const char* path) {
  std::vector<unsigned char> png;
  gfx::PNGCodec::ColorFormat color_format = gfx::PNGCodec::FORMAT_RGBA;
  if (!gfx::PNGCodec::Encode(
          reinterpret_cast<const unsigned char*>(bmp.getPixels()),
          color_format, gfx::Size(bmp.width(), bmp.height()),
          static_cast<int>(bmp.rowBytes()),
          false, std::vector<gfx::PNGCodec::Comment>(), &png)) {
    FAIL() << "Failed to encode image";
  }

  const base::FilePath fpath(path);
  if (!base::WriteFile(fpath, png)) {
    FAIL() << "Failed to write dest \"" << path << '"';
  }
}
#endif  // #if DEBUG_BITMAP_GENERATION

void CheckResampleToSame(skia::ImageOperations::ResizeMethod method) { … }

// Types defined outside of the ResizeShouldAverageColors test to allow
// use of the std::size() macro.
//
// 'max_color_distance_override' is used in a max() call together with
// the value of 'max_color_distance' defined in a TestedPixel instance.
// Hence a value of 0.0 in 'max_color_distance_override' means
// "use the pixel-specific value" and larger values can be used to allow
// worse computation errors than provided in a TestedPixel instance.
struct TestedResizeMethod { … };

struct TestedPixel { … };

// Helper function used by the test "ResizeShouldAverageColors" below.
// Note that ASSERT_EQ does a "return;" on failure, hence we can't have
// a "bool" return value to reflect success. Hence "all_pixels_pass"
void CheckResizeMethodShouldAverageGrid(
    const SkBitmap& src,
    const TestedResizeMethod& tested_method,
    int dest_w, int dest_h, SkColor average_color,
    bool* method_passed) { … }


}  // namespace

// Helper tests that saves bitmaps to PNGs in /tmp/ to visually check
// that the bitmap generation functions work as expected.
// Those tests are not enabled by default as verification is done
// manually/visually, however it is convenient to leave the functions
// in place.
#if 0 && DEBUG_BITMAP_GENERATION
TEST(ImageOperations, GenerateGradientBitmap) {
  // Make our source bitmap.
  const int src_w = 640, src_h = 480;
  SkBitmap src;
  FillDataToBitmap(src_w, src_h, &src);

  SaveBitmapToPNG(src, "/tmp/gradient_640x480.png");
}

TEST(ImageOperations, GenerateGridBitmap) {
  const int src_w = 640, src_h = 480, src_grid_pitch = 10, src_grid_width = 4;
  const SkColor grid_color = SK_ColorRED, background_color = SK_ColorBLUE;
  SkBitmap src;
  DrawGridToBitmap(src_w, src_h,
                   background_color, grid_color,
                   src_grid_pitch, src_grid_width,
                   &src);

  SaveBitmapToPNG(src, "/tmp/grid_640x408_10_4_red_blue.png");
}

TEST(ImageOperations, GenerateCheckerBitmap) {
  const int src_w = 640, src_h = 480, rect_w = 10, rect_h = 4;
  const SkColor color1 = SK_ColorRED, color2 = SK_ColorBLUE;
  SkBitmap src;
  DrawCheckerToBitmap(src_w, src_h, color1, color2, rect_w, rect_h, &src);

  SaveBitmapToPNG(src, "/tmp/checker_640x408_10_4_red_blue.png");
}
#endif  // #if ... && DEBUG_BITMAP_GENERATION

// Makes the bitmap 50% the size as the original using a box filter. This is
// an easy operation that we can check the results for manually.
TEST(ImageOperations, Halve) { … }

TEST(ImageOperations, HalveSubset) { … }

TEST(ImageOperations, InvalidParams) { … }

// Resamples an image to the same image, it should give the same result.
TEST(ImageOperations, ResampleToSameHamming1) { … }

TEST(ImageOperations, ResampleToSameLanczos3) { … }

// Check that all Good/Better/Best, Box, Lanczos2 and Lanczos3 generate purple
// when resizing a 4x8 red/blue checker pattern by 1/16x1/16.
TEST(ImageOperations, ResizeShouldAverageColors) { … }

static double sinc(double x) { … }

static double lanczos3(double offset) { … }

TEST(ImageOperations, ScaleUp) { … }
chromium/skia/ext/image_operations_unittest.cc
