fix(IBA): IBA::compare_Yee() accessed the wrong channel (#4976)

The GaussianPyramid::value() method used by IBA::compare_Yee() was
incorrectly accessing channel 1 instead of channel 0. This fix corrects the
channel access to properly retrieve the luminance value from the
single-channel pyramid levels.

One oddity this led to is that `idiff -p` would appear to PASS for
some clearly different images if they had different data windows.

Update reference outputs to reflect the corrected perceptual diff results
(Max error changes from 1 to 10 for the test images).

Fixes #4948

Signed-off-by: pmady <[email protected]>

Author: pmady

src/libOpenImageIO/imagebufalgo_yee.cpp

@@ -52,7 +52,7 @@ class GaussianPyramid {
         if (lev >= PYRAMID_MAX_LEVELS)
             return 0.0f;
         else
-            return level[lev].getchannel(x, y, 0, 1);
+            return level[lev].getchannel(x, y, 0, 0);
     }
 
 #if 0 /* unused */
@@ -65,7 +65,7 @@ class GaussianPyramid {
     float operator()(int x, int y, int lev) const
     {
         OIIO_DASSERT(lev < PYRAMID_MAX_LEVELS);
-        return level[lev].getchannel(x, y, 0, 1);
+        return level[lev].getchannel(x, y, 0, 0);
     }
 #endif
 

testsuite/diff/ref/out-fmt6.txt

@@ -16,7 +16,7 @@ Computing diff of "img1.exr" vs "img2.exr"
   121 pixels (2.95%) over 1e-06
 FAILURE
 Computing perceptual diff of "img1.exr" vs "img2.exr"
-  Max error  = 1.0 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10.0 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   121 pixels (2.95%) failed the perceptual test
 FAILURE
 Computing perceptual diff of "img1.exr" vs "img1.exr"
@@ -26,7 +26,7 @@ Comparing "img1.exr" and "img2.exr"
   Mean error = 0
   RMS error = 0
   Peak SNR = 0
-  Max error  = 1 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   0 pixels (0%) over 0.008
   121 pixels (2.95%) over 0.004
   121 pixels (2.9541%) failed the perceptual test
@@ -38,7 +38,7 @@ Comparing "img1.exr" and "img2.exr"
   Mean error = 0
   RMS error = 0
   Peak SNR = 0
-  Max error  = 1 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   0 pixels (0%) over 0.008
   121 pixels (2.95%) over 1.0
   121 pixels (2.9541%) failed the perceptual test

testsuite/diff/ref/out.txt

@@ -16,7 +16,7 @@ Computing diff of "img1.exr" vs "img2.exr"
   121 pixels (2.95%) over 1e-06
 FAILURE
 Computing perceptual diff of "img1.exr" vs "img2.exr"
-  Max error  = 1 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   121 pixels (2.95%) failed the perceptual test
 FAILURE
 Computing perceptual diff of "img1.exr" vs "img1.exr"
@@ -26,7 +26,7 @@ Comparing "img1.exr" and "img2.exr"
   Mean error = 0
   RMS error = 0
   Peak SNR = 0
-  Max error  = 1 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   0 pixels (0%) over 0.008
   121 pixels (2.95%) over 0.004
   121 pixels (2.9541%) failed the perceptual test
@@ -38,7 +38,7 @@ Comparing "img1.exr" and "img2.exr"
   Mean error = 0
   RMS error = 0
   Peak SNR = 0
-  Max error  = 1 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
+  Max error  = 10 @ (5, 17, R)  values are 0.1, 0.1, 0.1 vs 0.1, 0.6, 0.1
   0 pixels (0%) over 0.008
   121 pixels (2.95%) over 1
   121 pixels (2.9541%) failed the perceptual test