Add image_diff from the chromium repo.

sky/tools/imagediff/image_diff.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file input format is based loosely on
+// Tools/DumpRenderTree/ImageDiff.m
+
+// The exact format of this tool's output to stdout is important, to match
+// what the run-webkit-tests script expects.
+
+#include <algorithm>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/command_line.h"
+#include "base/containers/hash_tables.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/process/memory.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "sky/tools/imagediff/image_diff_png.h"
+
+#if defined(OS_WIN)
+#include "windows.h"
+#endif
+
+// Causes the app to remain open, waiting for pairs of filenames on stdin.
+// The caller is then responsible for terminating this app.
+static const char kOptionPollStdin[] = "use-stdin";
+// Causes the app to additionally calculate a diff of the color histograms
+// (which is resistant to shifts in layout).
+static const char kOptionCompareHistograms[] = "histogram";
+// Causes the app to output an image that visualizes the difference.
+static const char kOptionGenerateDiff[] = "diff";
+
+// Return codes used by this utility.
+static const int kStatusSame = 0;
+static const int kStatusDifferent = 1;
+static const int kStatusError = 2;
+
+// Color codes.
+static const uint32 RGBA_RED = 0x000000ff;
+static const uint32 RGBA_ALPHA = 0xff000000;
+
+class Image {
+ public:
+  Image() : w_(0), h_(0) {
+  }
+
+  Image(const Image& image)
+      : w_(image.w_),
+        h_(image.h_),
+        data_(image.data_) {
+  }
+
+  bool has_image() const {
+    return w_ > 0 && h_ > 0;
+  }
+
+  int w() const {
+    return w_;
+  }
+
+  int h() const {
+    return h_;
+  }
+
+  const unsigned char* data() const {
+    return &data_.front();
+  }
+
+  // Creates the image from stdin with the given data length. On success, it
+  // will return true. On failure, no other methods should be accessed.
+  bool CreateFromStdin(size_t byte_length) {
+    if (byte_length == 0)
+      return false;
+
+    scoped_ptr<unsigned char[]> source(new unsigned char[byte_length]);
+    if (fread(source.get(), 1, byte_length, stdin) != byte_length)
+      return false;
+
+    if (!image_diff_png::DecodePNG(source.get(), byte_length,
+                                   &data_, &w_, &h_)) {
+      Clear();
+      return false;
+    }
+    return true;
+  }
+
+  // Creates the image from the given filename on disk, and returns true on
+  // success.
+  bool CreateFromFilename(const base::FilePath& path) {
+    FILE* f = base::OpenFile(path, "rb");
+    if (!f)
+      return false;
+
+    std::vector<unsigned char> compressed;
+    const int buf_size = 1024;
+    unsigned char buf[buf_size];
+    size_t num_read = 0;
+    while ((num_read = fread(buf, 1, buf_size, f)) > 0) {
+      compressed.insert(compressed.end(), buf, buf + num_read);
+    }
+
+    base::CloseFile(f);
+
+    if (!image_diff_png::DecodePNG(&compressed[0], compressed.size(),
+                                   &data_, &w_, &h_)) {
+      Clear();
+      return false;
+    }
+    return true;
+  }
+
+  void Clear() {
+    w_ = h_ = 0;
+    data_.clear();
+  }
+
+  // Returns the RGBA value of the pixel at the given location
+  uint32 pixel_at(int x, int y) const {
+    DCHECK(x >= 0 && x < w_);
+    DCHECK(y >= 0 && y < h_);
+    return *reinterpret_cast<const uint32*>(&(data_[(y * w_ + x) * 4]));
+  }
+
+  void set_pixel_at(int x, int y, uint32 color) const {
+    DCHECK(x >= 0 && x < w_);
+    DCHECK(y >= 0 && y < h_);
+    void* addr = &const_cast<unsigned char*>(&data_.front())[(y * w_ + x) * 4];
+    *reinterpret_cast<uint32*>(addr) = color;
+  }
+
+ private:
+  // pixel dimensions of the image
+  int w_, h_;
+
+  std::vector<unsigned char> data_;
+};
+
+float PercentageDifferent(const Image& baseline, const Image& actual) {
+  int w = std::min(baseline.w(), actual.w());
+  int h = std::min(baseline.h(), actual.h());
+
+  // Compute pixels different in the overlap.
+  int pixels_different = 0;
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      if (baseline.pixel_at(x, y) != actual.pixel_at(x, y))
+        pixels_different++;
+    }
+  }
+
+  // Count pixels that are a difference in size as also being different.
+  int max_w = std::max(baseline.w(), actual.w());
+  int max_h = std::max(baseline.h(), actual.h());
+  // These pixels are off the right side, not including the lower right corner.
+  pixels_different += (max_w - w) * h;
+  // These pixels are along the bottom, including the lower right corner.
+  pixels_different += (max_h - h) * max_w;
+
+  // Like the WebKit ImageDiff tool, we define percentage different in terms
+  // of the size of the 'actual' bitmap.
+  float total_pixels = static_cast<float>(actual.w()) *
+                       static_cast<float>(actual.h());
+  if (total_pixels == 0) {
+    // When the bitmap is empty, they are 100% different.
+    return 100.0f;
+  }
+  return 100.0f * pixels_different / total_pixels;
+}
+
+typedef base::hash_map<uint32, int32> RgbaToCountMap;
+
+float HistogramPercentageDifferent(const Image& baseline, const Image& actual) {
+  // TODO(johnme): Consider using a joint histogram instead, as described in
+  // "Comparing Images Using Joint Histograms" by Pass & Zabih
+  // http://www.cs.cornell.edu/~rdz/papers/pz-jms99.pdf
+
+  int w = std::min(baseline.w(), actual.w());
+  int h = std::min(baseline.h(), actual.h());
+
+  // Count occurences of each RGBA pixel value of baseline in the overlap.
+  RgbaToCountMap baseline_histogram;
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      // hash_map operator[] inserts a 0 (default constructor) if key not found.
+      baseline_histogram[baseline.pixel_at(x, y)]++;
+    }
+  }
+
+  // Compute pixels different in the histogram of the overlap.
+  int pixels_different = 0;
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      uint32 actual_rgba = actual.pixel_at(x, y);
+      RgbaToCountMap::iterator it = baseline_histogram.find(actual_rgba);
+      if (it != baseline_histogram.end() && it->second > 0)
+        it->second--;
+      else
+        pixels_different++;
+    }
+  }
+
+  // Count pixels that are a difference in size as also being different.
+  int max_w = std::max(baseline.w(), actual.w());
+  int max_h = std::max(baseline.h(), actual.h());
+  // These pixels are off the right side, not including the lower right corner.
+  pixels_different += (max_w - w) * h;
+  // These pixels are along the bottom, including the lower right corner.
+  pixels_different += (max_h - h) * max_w;
+
+  // Like the WebKit ImageDiff tool, we define percentage different in terms
+  // of the size of the 'actual' bitmap.
+  float total_pixels = static_cast<float>(actual.w()) *
+                       static_cast<float>(actual.h());
+  if (total_pixels == 0) {
+    // When the bitmap is empty, they are 100% different.
+    return 100.0f;
+  }
+  return 100.0f * pixels_different / total_pixels;
+}
+
+void PrintHelp() {
+  fprintf(stderr,
+    "Usage:\n"
+    "  image_diff [--histogram] <compare file> <reference file>\n"
+    "    Compares two files on disk, returning 0 when they are the same;\n"
+    "    passing \"--histogram\" additionally calculates a diff of the\n"
+    "    RGBA value histograms (which is resistant to shifts in layout)\n"
+    "  image_diff --use-stdin\n"
+    "    Stays open reading pairs of filenames from stdin, comparing them,\n"
+    "    and sending 0 to stdout when they are the same\n"
+    "  image_diff --diff <compare file> <reference file> <output file>\n"
+    "    Compares two files on disk, outputs an image that visualizes the\n"
+    "    difference to <output file>\n");
+  /* For unfinished webkit-like-mode (see below)
+    "\n"
+    "  image_diff -s\n"
+    "    Reads stream input from stdin, should be EXACTLY of the format\n"
+    "    \"Content-length: <byte length> <data>Content-length: ...\n"
+    "    it will take as many file pairs as given, and will compare them as\n"
+    "    (cmp_file, reference_file) pairs\n");
+  */
+}
+
+int CompareImages(const base::FilePath& file1,
+                  const base::FilePath& file2,
+                  bool compare_histograms) {
+  Image actual_image;
+  Image baseline_image;
+
+  if (!actual_image.CreateFromFilename(file1)) {
+    fprintf(stderr, "image_diff: Unable to open file \"%" PRFilePath "\"\n",
+            file1.value().c_str());
+    return kStatusError;
+  }
+  if (!baseline_image.CreateFromFilename(file2)) {
+    fprintf(stderr, "image_diff: Unable to open file \"%" PRFilePath "\"\n",
+            file2.value().c_str());
+    return kStatusError;
+  }
+
+  if (compare_histograms) {
+    float percent = HistogramPercentageDifferent(actual_image, baseline_image);
+    const char* passed = percent > 0.0 ? "failed" : "passed";
+    printf("histogram diff: %01.2f%% %s\n", percent, passed);
+  }
+
+  const char* diff_name = compare_histograms ? "exact diff" : "diff";
+  float percent = PercentageDifferent(actual_image, baseline_image);
+  const char* passed = percent > 0.0 ? "failed" : "passed";
+  printf("%s: %01.2f%% %s\n", diff_name, percent, passed);
+  if (percent > 0.0) {
+    // failure: The WebKit version also writes the difference image to
+    // stdout, which seems excessive for our needs.
+    return kStatusDifferent;
+  }
+  // success
+  return kStatusSame;
+
+/* Untested mode that acts like WebKit's image comparator. I wrote this but
+   decided it's too complicated. We may use it in the future if it looks useful
+
+  char buffer[2048];
+  while (fgets(buffer, sizeof(buffer), stdin)) {
+
+    if (strncmp("Content-length: ", buffer, 16) == 0) {
+      char* context;
+      strtok_s(buffer, " ", &context);
+      int image_size = strtol(strtok_s(NULL, " ", &context), NULL, 10);
+
+      bool success = false;
+      if (image_size > 0 && actual_image.has_image() == 0) {
+        if (!actual_image.CreateFromStdin(image_size)) {
+          fputs("Error, input image can't be decoded.\n", stderr);
+          return 1;
+        }
+      } else if (image_size > 0 && baseline_image.has_image() == 0) {
+        if (!baseline_image.CreateFromStdin(image_size)) {
+          fputs("Error, baseline image can't be decoded.\n", stderr);
+          return 1;
+        }
+      } else {
+        fputs("Error, image size must be specified.\n", stderr);
+        return 1;
+      }
+    }
+
+    if (actual_image.has_image() && baseline_image.has_image()) {
+      float percent = PercentageDifferent(actual_image, baseline_image);
+      if (percent > 0.0) {
+        // failure: The WebKit version also writes the difference image to
+        // stdout, which seems excessive for our needs.
+        printf("diff: %01.2f%% failed\n", percent);
+      } else {
+        // success
+        printf("diff: %01.2f%% passed\n", percent);
+      }
+      actual_image.Clear();
+      baseline_image.Clear();
+    }
+
+    fflush(stdout);
+  }
+*/
+}
+
+bool CreateImageDiff(const Image& image1, const Image& image2, Image* out) {
+  int w = std::min(image1.w(), image2.w());
+  int h = std::min(image1.h(), image2.h());
+  *out = Image(image1);
+  bool same = (image1.w() == image2.w()) && (image1.h() == image2.h());
+
+  // TODO(estade): do something with the extra pixels if the image sizes
+  // are different.
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      uint32 base_pixel = image1.pixel_at(x, y);
+      if (base_pixel != image2.pixel_at(x, y)) {
+        // Set differing pixels red.
+        out->set_pixel_at(x, y, RGBA_RED | RGBA_ALPHA);
+        same = false;
+      } else {
+        // Set same pixels as faded.
+        uint32 alpha = base_pixel & RGBA_ALPHA;
+        uint32 new_pixel = base_pixel - ((alpha / 2) & RGBA_ALPHA);
+        out->set_pixel_at(x, y, new_pixel);
+      }
+    }
+  }
+
+  return same;
+}
+
+int DiffImages(const base::FilePath& file1, const base::FilePath& file2,
+               const base::FilePath& out_file) {
+  Image actual_image;
+  Image baseline_image;
+
+  if (!actual_image.CreateFromFilename(file1)) {
+    fprintf(stderr, "image_diff: Unable to open file \"%" PRFilePath "\"\n",
+            file1.value().c_str());
+    return kStatusError;
+  }
+  if (!baseline_image.CreateFromFilename(file2)) {
+    fprintf(stderr, "image_diff: Unable to open file \"%" PRFilePath "\"\n",
+            file2.value().c_str());
+    return kStatusError;
+  }
+
+  Image diff_image;
+  bool same = CreateImageDiff(baseline_image, actual_image, &diff_image);
+  if (same)
+    return kStatusSame;
+
+  std::vector<unsigned char> png_encoding;
+  image_diff_png::EncodeRGBAPNG(
+      diff_image.data(), diff_image.w(), diff_image.h(),
+      diff_image.w() * 4, &png_encoding);
+  if (base::WriteFile(out_file,
+          reinterpret_cast<char*>(&png_encoding.front()),
+          base::checked_cast<int>(png_encoding.size())) < 0)
+    return kStatusError;
+
+  return kStatusDifferent;
+}
+
+// It isn't strictly correct to only support ASCII paths, but this
+// program reads paths on stdin and the program that spawns it outputs
+// paths as non-wide strings anyway.
+base::FilePath FilePathFromASCII(const std::string& str) {
+#if defined(OS_WIN)
+  return base::FilePath(base::ASCIIToUTF16(str));
+#else
+  return base::FilePath(str);
+#endif
+}
+
+int main(int argc, const char* argv[]) {
+  base::EnableTerminationOnHeapCorruption();
+  CommandLine::Init(argc, argv);
+  const CommandLine& parsed_command_line = *CommandLine::ForCurrentProcess();
+  bool histograms = parsed_command_line.HasSwitch(kOptionCompareHistograms);
+  if (parsed_command_line.HasSwitch(kOptionPollStdin)) {
+    // Watch stdin for filenames.
+    std::string stdin_buffer;
+    base::FilePath filename1;
+    while (std::getline(std::cin, stdin_buffer)) {
+      if (stdin_buffer.empty())
+        continue;
+
+      if (!filename1.empty()) {
+        // CompareImages writes results to stdout unless an error occurred.
+        base::FilePath filename2 = FilePathFromASCII(stdin_buffer);
+        if (CompareImages(filename1, filename2, histograms) == kStatusError)
+          printf("error\n");
+        fflush(stdout);
+        filename1 = base::FilePath();
+      } else {
+        // Save the first filename in another buffer and wait for the second
+        // filename to arrive via stdin.
+        filename1 = FilePathFromASCII(stdin_buffer);
+      }
+    }
+    return 0;
+  }
+
+  const CommandLine::StringVector& args = parsed_command_line.GetArgs();
+  if (parsed_command_line.HasSwitch(kOptionGenerateDiff)) {
+    if (args.size() == 3) {
+      return DiffImages(base::FilePath(args[0]),
+                        base::FilePath(args[1]),
+                        base::FilePath(args[2]));
+    }
+  } else if (args.size() == 2) {
+    return CompareImages(
+        base::FilePath(args[0]), base::FilePath(args[1]), histograms);
+  }
+
+  PrintHelp();
+  return kStatusError;
+}