Complete (but inefficient) implementation of the image retargetting method.

skia/ext/convolver_unittest.cc

Index: skia/ext/convolver_unittest.cc
diff --git a/skia/ext/convolver_unittest.cc b/skia/ext/convolver_unittest.cc
index 377ed8ed3051c20f491ad0336d8bed80a3041b17..567f5df7fc1de5e681edd4ee46ba9951ac1beef8 100644
--- a/skia/ext/convolver_unittest.cc
+++ b/skia/ext/convolver_unittest.cc
@@ -324,4 +324,164 @@ TEST(Convolver, SIMDVerification) {
   }
 }
 
+TEST(Convolver, SeparableSingleConvolution) {
+  static const int kSize = 1024;
+  static const int kChannelCount = 3;
+  static const int kStrideSlack = 22;
+  ConvolutionFilter1D filter;
+  const float box[5] = { 0.2, 0.2, 0.2, 0.2, 0.2 };
+  filter.AddFilter(0, box, 5);
+
+  // Allocate a source image and set to 0.
+  int img_width = kSize;

[Alexei Svitkine (slow), 2013/04/11 18:25:37]

Do you need all these temp variables?

e.g. can you just use kSize directly?

Also, everything that's not changing after init, please make const.

[motek., 2013/04/12 10:50:59]

Nah, I don't need them. Copied as such from a routine above. Fixed up as
suggested.

+  int img_height = kSize;
+  int src_row_stride = img_width * kChannelCount + kStrideSlack;
+  int src_byte_count = src_row_stride * img_height;
+  std::vector<unsigned char> input;
+  int signal_x = img_width / 2;
+  int signal_y = img_height / 2;
+  input.resize(src_byte_count, 0);
+  // The image has a single impulse pixel in channel 1, smack in the middle.
+  int non_zero_pixel_index =
+      signal_y * src_row_stride + signal_x * kChannelCount + 1;
+  input[non_zero_pixel_index] = 255;
+
+  // Destination will be a single channel image with stide matching width.
+  int dest_row_stride = img_width;
+  int dest_byte_count = dest_row_stride * img_height;
+  std::vector<unsigned char> output;
+  output.resize(dest_byte_count);
+
+  // Apply convolution in X.
+  SingleChannelConvolveX1D(&input[0], src_row_stride, 1, kChannelCount,
+                           filter, SkISize::Make(img_width, img_height),
+                           &output[0], dest_row_stride, 0, 1, false);
+  for (int x = signal_x - 2; x <= signal_x + 2; ++x) {

[Alexei Svitkine (slow), 2013/04/11 18:25:37]

Nit: No need for {}'s.

[motek., 2013/04/12 10:50:59]

Done.

+    EXPECT_GT(output[signal_y * dest_row_stride + x], 0);
+  }
+  EXPECT_EQ(output[signal_y * dest_row_stride + signal_x - 3], 0);
+  EXPECT_EQ(output[signal_y * dest_row_stride + signal_x + 3], 0);
+
+  // Apply convolution in Y.
+  SingleChannelConvolveY1D(&input[0], src_row_stride, 1, kChannelCount,
+                           filter, SkISize::Make(img_width, img_height),
+                           &output[0], dest_row_stride, 0, 1, false);
+  for (int y = signal_y - 2; y <= signal_y + 2; ++y) {

[Alexei Svitkine (slow), 2013/04/11 18:25:37]

Nit: No need for {}'s.

[motek., 2013/04/12 10:50:59]

Done.

+    EXPECT_GT(output[y * dest_row_stride + signal_x], 0);
+  }
+
+  EXPECT_EQ(output[(signal_y - 3) * dest_row_stride + signal_x], 0);
+  EXPECT_EQ(output[(signal_y + 3) * dest_row_stride + signal_x], 0);
+
+  EXPECT_EQ(output[signal_y * dest_row_stride + signal_x - 1], 0);
+  EXPECT_EQ(output[signal_y * dest_row_stride + signal_x + 1], 0);
+
+  // The main point of calling this is to invoke the routine on input without
+  // padding.
+  std::vector<unsigned char> output2;
+  output2.resize(dest_byte_count);
+  SingleChannelConvolveX1D(&output[0], dest_row_stride, 0, 1,
+                           filter, SkISize::Make(img_width, img_height),
+                           &output2[0], dest_row_stride, 0, 1, false);
+  // This should be a result of 2D convolution.
+  for (int x = signal_x - 2; x <= signal_x + 2; ++x) {
+    for (int y = signal_y - 2; y <= signal_y + 2; ++y) {
+      EXPECT_GT(output2[y * dest_row_stride + x], 0);
+    }
+  }
+  EXPECT_EQ(output2[0], 0);
+  EXPECT_EQ(output2[dest_row_stride - 1], 0);
+  EXPECT_EQ(output2[dest_byte_count - 1], 0);
+}
+
+TEST(Convolver, SeparableSingleConvolutionEdges) {
+  // The purpose of this test is to check if the implementation treats correctly
+  // edges of the image.
+  static const int kImgWidth = 600;
+  static const int kImgHeight = 800;
+  static const int kChannelCount = 3;
+  static const int kStrideSlack = 22;
+  static const int kChannel = 1;
+  ConvolutionFilter1D filter;
+  const float box[5] = { 0.2, 0.2, 0.2, 0.2, 0.2 };
+  filter.AddFilter(0, box, 5);
+
+  // Allocate a source image and set to 0.
+  int src_row_stride = kImgWidth * kChannelCount + kStrideSlack;
+  int src_byte_count = src_row_stride * kImgHeight;
+  std::vector<unsigned char> input(src_byte_count);
+
+  // Draw a frame around the image.
+  for (int i = 0; i < src_byte_count; ++i) {
+    int row = i / src_row_stride;
+    int col = i % src_row_stride / kChannelCount;
+    int channel = i % src_row_stride % kChannelCount;
+    if (channel != kChannel || col > kImgWidth) {
+      input[i] = 255;
+    } else if (row == 0 || col == 0 ||
+               col == kImgWidth - 1 || row == kImgHeight - 1) {
+      input[i] = 100;
+    } else if (row == 1 || col == 1 ||
+               col == kImgWidth - 2 || row == kImgHeight - 2) {
+      input[i] = 200;
+    } else {
+      input[i] = 0;
+    }
+  }
+
+  // Destination will be a single channel image with stide matching width.
+  int dest_row_stride = kImgWidth;
+  int dest_byte_count = dest_row_stride * kImgHeight;
+  std::vector<unsigned char> output;
+  output.resize(dest_byte_count);
+
+  // Apply convolution in X.
+  SingleChannelConvolveX1D(&input[0], src_row_stride, 1, kChannelCount,
+                           filter, SkISize::Make(kImgWidth, kImgHeight),
+                           &output[0], dest_row_stride, 0, 1, false);
+
+  // Sadly, comparison is not as simple as retaining all values.
+  int invalid_values = 0;
+  const unsigned char first_value = output[0];
+  EXPECT_TRUE(std::abs(100 - first_value) <= 1);
+  for (int i = 0; i < dest_row_stride; ++i) {
+    if (output[i] != first_value)
+      ++invalid_values;
+  }
+  EXPECT_EQ(0, invalid_values);
+
+  int test_row = 22;
+  EXPECT_TRUE(std::abs(output[test_row * dest_row_stride] - 100) <= 1);
+  EXPECT_TRUE(std::abs(output[test_row * dest_row_stride + 1] - 80) <= 1);
+  EXPECT_TRUE(std::abs(output[test_row * dest_row_stride + 2] - 60) <= 1);
+  EXPECT_TRUE(std::abs(output[test_row * dest_row_stride + 3] - 40) <= 1);
+  EXPECT_TRUE(

[Alexei Svitkine (slow), 2013/04/11 18:25:37]

Can you use EXPECT_NEAR() for these?

[motek., 2013/04/12 10:50:59]

Done.

+      std::abs(output[(test_row + 1) * dest_row_stride - 1] - 100) <= 1);
+  EXPECT_TRUE(
+      std::abs(output[(test_row + 1) * dest_row_stride - 2] - 80) <= 1);
+  EXPECT_TRUE(
+      std::abs(output[(test_row + 1) * dest_row_stride - 3] - 60) <= 1);
+  EXPECT_TRUE(
+      std::abs(output[(test_row + 1) * dest_row_stride - 4] - 40) <= 1);
+
+  SingleChannelConvolveY1D(&input[0], src_row_stride, 1, kChannelCount,
+                           filter, SkISize::Make(kImgWidth, kImgHeight),
+                           &output[0], dest_row_stride, 0, 1, false);
+
+  int test_column = 42;
+  EXPECT_TRUE(std::abs(output[test_column] - 100) <= 1);
+  EXPECT_TRUE(std::abs(output[test_column + dest_row_stride] - 80) <= 1);
+  EXPECT_TRUE(std::abs(output[test_column + dest_row_stride * 2] - 60) <= 1);
+  EXPECT_TRUE(std::abs(output[test_column + dest_row_stride * 3] - 40) <= 1);
+
+  EXPECT_TRUE(std::abs(
+      output[test_column + dest_row_stride * (kImgHeight - 1)] - 100) <= 1);
+  EXPECT_TRUE(std::abs(
+      output[test_column + dest_row_stride * (kImgHeight - 2)] - 80) <= 1);
+  EXPECT_TRUE(std::abs(
+      output[test_column + dest_row_stride * (kImgHeight - 3)] - 60) <= 1);
+  EXPECT_TRUE(std::abs(
+      output[test_column + dest_row_stride * (kImgHeight - 4)] - 40) <= 1);
+}
+
 }  // namespace skia