fix(oiiotool): Ignore empty subimage(s) when calculating non-zero region (#4909)

Fixes #4799

When trimming an image that contains an empty subimage, the resulting
ROI unexpectedly included the top-left pixel even if zero in all
subimages.

To avoid this, empty ROIs are ignored when computing the overall
non-zero region.
If all subimages are empty, the first subimage ROI is used and doctored
to be 1 pixel.

Two tests have been added to the oiiotool testsuite:
 - 1 to check the trimming of an empty image
 - 1 to check the trimming of a non-empty image with an empty subimage

Signed-off-by: Carine Touraille <[email protected]>

Author: kookiCT

src/oiiotool/oiiotool.cpp

@@ -4077,14 +4077,17 @@ nonzero_region_all_subimages(ImageRecRef A)
     ROI nonzero_region;
     for (int s = 0; s < A->subimages(); ++s) {
         ROI roi = ImageBufAlgo::nonzero_region((*A)(s));
-        if (roi.npixels() == 0) {
-            // Special case -- all zero; but doctor to make it 1 zero pixel
-            roi      = (*A)(s).roi();
-            roi.xend = roi.xbegin + 1;
-            roi.yend = roi.ybegin + 1;
-            roi.zend = roi.zbegin + 1;
+        if (roi.npixels() != 0) {
+            nonzero_region = roi_union(nonzero_region, roi);
         }
-        nonzero_region = roi_union(nonzero_region, roi);
+    }
+    if (!nonzero_region.defined()) {
+        // Special case -- all zero
+        // fallback to 1st subimage ROI, but doctor to make it 1 zero pixel
+        nonzero_region      = (*A)(0).roi();
+        nonzero_region.xend = nonzero_region.xbegin + 1;
+        nonzero_region.yend = nonzero_region.ybegin + 1;
+        nonzero_region.zend = nonzero_region.zbegin + 1;
     }
     return nonzero_region;
 }

testsuite/oiiotool/ref/out.txt

@@ -68,8 +68,12 @@ Comparing "autotrim.tif" and "ref/autotrim.tif"
 PASS
 Comparing "trim.tif" and "ref/trim.tif"
 PASS
+Comparing "trimempty.tif" and "ref/trimempty.tif"
+PASS
 Comparing "trimsubimages.tif" and "ref/trimsubimages.tif"
 PASS
+Comparing "trimemptysubimages.tif" and "ref/trimemptysubimages.tif"
+PASS
 Comparing "add.exr" and "ref/add.exr"
 PASS
 Comparing "cadd1.exr" and "ref/cadd1.exr"

testsuite/oiiotool/ref/trimempty.tif

@@ -105,11 +105,21 @@
 command += oiiotool ("--create 320x240 3 -fill:color=.1,.5,.1 120x80+50+70 "
                      + " -rotate 30 -trim -origin +0+0 -fullpixels -d uint8 -o trim.tif")
 
+# test --trim on empty image
+command += oiiotool ("--create 320x240 3 "
+                     + " -trim -origin +0+0 -fullpixels -d uint8 -o trimempty.tif")
+
 # test --trim, tricky case of multiple subimages
 command += oiiotool (  "-a --create 320x240 3 -fill:color=.1,.5,.1 120x80+50+70 -rotate 30 "
                      + "--create 320x240 3 -fill:color=.5,.5,.1 100x10+70+70 -rotate 140 "
                      + "--siappend -trim -origin +0+0 -fullpixels -d uint8 -o trimsubimages.tif")
 
+# test --trim, tricky case of multiple subimages including one empty one
+command += oiiotool (  "-a --create 320x240 3 -fill:color=.1,.5,.1 120x80+50+70 -rotate 30 "
+                     + "--create 320x240 3 -fill:color=.5,.5,.1 100x10+70+70 -rotate 140 "
+                     + "--create 320x240 3 "
+                     + "--siappendall -trim -origin +0+0 -fullpixels -d uint8 -o trimemptysubimages.tif")
+
 # test hole filling
 command += oiiotool ("ref/hole.tif --fillholes -o tahoe-filled.tif")
 # test hole filling for a cropped image
@@ -262,7 +272,8 @@
 outputs = [
             "filled.tif",
             "autotrim.tif",
-            "trim.tif", "trimsubimages.tif",
+            "trim.tif", "trimempty.tif",
+            "trimsubimages.tif", "trimemptysubimages.tif",
             "add.exr", "cadd1.exr", "cadd2.exr",
             "sub.exr", "subc.exr",
             "mul.exr", "cmul1.exr", "cmul2.exr",