Bug fix in deep image compare when pixels had different # of samples

The IBA::compare for deep images A and B would loop over pixels in the
union of A's and B's ROIs (so far, so good), then for each pixel would
loop from 0 to A's number of samples in that pixel. Oops! That means
that if A had fewer samples than B (or if A had no samples but B had
samples) in that pixel, it would not notice that the images were
different.

Author: lgritz

src/libOpenImageIO/imagebufalgo_compare.cpp

@@ -297,8 +297,9 @@ compare_(const ImageBuf& A, const ImageBuf& B, float failthresh,
         if (deep) {
             for (int i = 0; i < batchsize && !a.done(); ++i, ++a, ++b) {
                 bool warned = false, failed = false;  // For this pixel
+                auto nsamps = std::max(a.deep_samples(), b.deep_samples());
                 for (int c = roi.chbegin; c < roi.chend; ++c)
-                    for (int s = 0, e = a.deep_samples(); s < e; ++s) {
+                    for (int s = 0, e = nsamps; s < e; ++s) {
                         compare_value(a, c, a.deep_value(c, s),
                                       b.deep_value(c, s), result, maxval,
                                       batcherror, batch_sqrerror, failed,

testsuite/oiiotool-deep/ref/out.txt

@@ -1,3 +1,19 @@
+Computing diff of "src/deep-nosamples.exr" vs "src/deep-onesample.exr"
+  Mean error = 42
+  RMS error = 42
+  Peak SNR = 0
+  Max error  = 42 @ (0, 0, Z)
+  1 pixels (100%) over 1e-06
+  0 pixels (0%) over 100
+WARNING
+Computing diff of "src/deep-onesample.exr" vs "src/deep-nosamples.exr"
+  Mean error = 42
+  RMS error = 42
+  Peak SNR = 0
+  Max error  = 42 @ (0, 0, Z)
+  1 pixels (100%) over 1e-06
+  0 pixels (0%) over 100
+WARNING
 Comparing "flat.exr" and "ref/flat.exr"
 PASS
 Comparing "ch.exr" and "ref/ch.exr"

testsuite/oiiotool-deep/run.py

@@ -40,6 +40,26 @@
 # --resample
 command += oiiotool (exrdir+"/Balls.exr -resample 128x72 -o resampled-balls.exr")
 
+
+
+# Regression test: it used to be that comparing deep image, it would loop
+# only over A's samples, so if A had no samples in a pixel but B had
+# samples, then the comparison would fail to see a difference. Be sure to
+# test both orderings.
+# Compare with both orderings
+command += oiiotool ("--fail 100 src/deep-nosamples.exr src/deep-onesample.exr --diff")
+command += oiiotool ("--fail 100 src/deep-onesample.exr src/deep-nosamples.exr --diff")
+ # Recipe for creating the files:
+ # spec = oiio.ImageSpec (1, 1, 1, oiio.TypeDesc.TypeFloat)
+ # spec.channelnames = ("Z")
+ # spec.deep = True
+ # buf = oiio.ImageBuf (spec)
+ # buf.write ("src/deep-nosamples.exr")  # write a deep image with no samples
+ # buf.set_deep_samples (0, 0, 0, 1)
+ # buf.set_deep_value (0, 0, 0, 0, 0, 42.0)
+ # buf.write ("src/deep-onesample.exr")  # write another deep image with 1 sample
+
+
 # To add more tests, just append more lines like the above and also add
 # the new 'feature.tif' (or whatever you call it) to the outputs list,
 # below.