silent error with wide images

[dgutson]

git-diff-image silently fails with wide images.
By doing this change:

diff --git a/diff-image b/diff-image
index 1da14a4..0dbcfdb 100755
--- a/diff-image
+++ b/diff-image
@@ -195,7 +195,7 @@ density_flag=
 do_compare()
 {
     compare $density_flag $color_flag $fuzz_flag $backgroundcolor_flag "$f1" "$f2" png:- | \
-        montage $density_flag -geometry +4+4 $backgroundcolor_flag "$f1" - "$f2" png:- >"$destfile" 2>/dev/null || true
+        montage $density_flag -geometry +4+4 $backgroundcolor_flag "$f1" - "$f2" png:- >"$destfile"
 }

 if which xdg-open > /dev/null

compare throws this error:

montage-im6.q16: width or height exceeds limit `png:-' @ error/cache.c/OpenPixelCache/3909.

Please allow larger images, and consider some sort of error reporting.

[dgutson]

The workaround I found was to modify
sudo nano /etc/ImageMagick-6/policy.xml
duplicating the width:
<policy domain="resource" name="width" value="32KP"/>
(it was 16KP originally).

Maybe there is a flag to override this policy.

[ewanmellor]

I don't remember why I'm squelching errors from montage there. It's been there since day 1. I presume it's noisy in some other situation; I wouldn't have done that otherwise. If we can get montage to be quiet normally then that would be best.

If there's a flag to override the policy setting I'd happily take that patch, but I can't find it in their documentation.

Marking this as "help wanted" for now.