commit 65f492ab8038f6ec25547faad1c659bc62f8480b
author Nick Deakin <deakin@google.com> Tue Nov 29 22:47:40 2022 -0500
committer Nick Deakin <deakin@google.com> Tue Nov 29 23:00:45 2022 -0500
tree d11ff672bde622a42cc4590a662c1822aaa74e71
parent 1be799e7263029c60e36f4e58d7ecd4f79921e9e

Add RecoveryMapMath tests; also some fixes.

Add thorough tests for recovery map math. Also, the following fixes for
issues discovered along the way:
  * Added proper scaling of luminances during map generation
  * Corrected some luminance and color conversions using incorrect
    luminance/luma cooeficients
  * Corrected PQ inverse OETF
  * Corrected clipping of gain when encoding recovery
  * Corrected sampleMap to use a better, working sampling algorithm
    instead of the previous bad and incorrect one
  * Clarified expected ranges in and out of some transformation
    functions
  * Clarified references for a bunch of transformations

Bug: 252835416
Test: builds, new tests pass
Change-Id: I3c2192e840b784774c60cf212aaf188501915340

libs/jpegrecoverymap/recoverymap.cpp

diff --git a/libs/jpegrecoverymap/recoverymap.cpp b/libs/jpegrecoverymap/recoverymap.cpp
index 4a209ec..f7f3622 100644
--- a/libs/jpegrecoverymap/recoverymap.cpp
+++ b/libs/jpegrecoverymap/recoverymap.cpp
@@ -390,12 +390,15 @@
   map_data.reset(reinterpret_cast<uint8_t*>(dest->data));
 
   ColorTransformFn hdrInvOetf = nullptr;
+  float hdr_white_nits = 0.0f;
   switch (metadata->transferFunction) {
     case JPEGR_TF_HLG:
       hdrInvOetf = hlgInvOetf;
+      hdr_white_nits = kHlgMaxNits;
       break;
     case JPEGR_TF_PQ:
       hdrInvOetf = pqInvOetf;
+      hdr_white_nits = kPqMaxNits;
       break;
   }
 
@@ -426,7 +429,7 @@
       Color hdr_rgb_gamma = bt2100YuvToRgb(hdr_yuv_gamma);
       Color hdr_rgb = hdrInvOetf(hdr_rgb_gamma);
       hdr_rgb = hdrGamutConversionFn(hdr_rgb);
-      float hdr_y_nits = luminanceFn(hdr_rgb);
+      float hdr_y_nits = luminanceFn(hdr_rgb) * hdr_white_nits;
 
       hdr_y_nits_avg += hdr_y_nits;
       if (hdr_y_nits > hdr_y_nits_max) {
@@ -448,13 +451,13 @@
                                          kMapDimensionScaleFactor, x, y);
       Color sdr_rgb_gamma = srgbYuvToRgb(sdr_yuv_gamma);
       Color sdr_rgb = srgbInvOetf(sdr_rgb_gamma);
-      float sdr_y_nits = luminanceFn(sdr_rgb);
+      float sdr_y_nits = luminanceFn(sdr_rgb) * kSdrWhiteNits;
 
       Color hdr_yuv_gamma = sampleP010(uncompressed_p010_image, kMapDimensionScaleFactor, x, y);
       Color hdr_rgb_gamma = bt2100YuvToRgb(hdr_yuv_gamma);
       Color hdr_rgb = hdrInvOetf(hdr_rgb_gamma);
       hdr_rgb = hdrGamutConversionFn(hdr_rgb);
-      float hdr_y_nits = luminanceFn(hdr_rgb);
+      float hdr_y_nits = luminanceFn(hdr_rgb) * hdr_white_nits;
 
       size_t pixel_idx =  x + y * map_width;
       reinterpret_cast<uint8_t*>(dest->data)[pixel_idx] =