Add MS-SSIM VRS file compare

Summary:
In order to control compression quality, we need to be able to compare VRS files using an algorithm that can compare image differences and provide a score. The FileImageCompare facility will compare VRS files, using a filtered reader so we don't necessarily have to read every single frame (which can be slow).

meta:
Ocean provides an MS-SSIM implementation, which is an industry standard which we can simply depend on.

Reviewed By: kiminoue7

Differential Revision: D51345482

fbshipit-source-id: 3cc6d9c70b62cc9239ca01e2ea05bb74567620ed

vrs/test/helpers/VRSTestsHelpers.h

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#pragma once
+
 #include <functional>
 #include <string>
 

vrs/utils/PixelFrame.cpp

@@ -658,6 +658,10 @@ bool PixelFrame::normalizeToPixelFormat(
   return false;
 }
 
+bool PixelFrame::ssimCompare(const PixelFrame& other, double& meanSSIM, double& meanContrast) {
+  XR_LOGE_ONCE("PixelFrame::ssimCompare has no open source implementation");
+}
+
 #endif // !IS_VRS_OSS_CODE()
 
 } // namespace vrs::utils

vrs/utils/PixelFrame.h

@@ -274,6 +274,13 @@ class PixelFrame {
   /// @return True if the conversion was performed, false if source wasn't an RGBA frame.
   bool convertRgbaToRgb(shared_ptr<PixelFrame>& outRgbFrame) const;
 
+  /// Compare this image with another image, and return an MS-SSIM score.
+  /// @param other: the other image to compare with.
+  /// @param msssim: on exit, the MS-SSIM score.
+  /// @return True if the images have identical dimensions and pixel formats, the pixel format is
+  /// supported (grey8 or rgb8), and the comparison succeeded.
+  bool msssimCompare(const PixelFrame& other, double& msssim);
+
  private:
   /// Conversion from an external buffer
   /// @param convertedFrame: frame to convert to. May not be allocated yet.