Cannot create thumbnail in ImageMagick: "convert: no decode delegate for this image format" - imagemagick

Question

I've been at this all day. I'm trying to upload images to a Mediawiki and this is the error I get when ImageMagick tries to create the thumbnail:
Error creating thumbnail: convert: no decode delegate for this image format `/tmp/magick-11924QG1rRXzT948I' # error/constitute.c/ReadImage/552.
convert: no images defined `/tmp/s3thumb-cripEh' # error/convert.c/ConvertImageCommand/3127.
I setup a debug file for mediawiki and this is what I get in the log:
BitmapHandler::doTransform: creating 112x120 thumbnail at /tmp/s3thumb-cripEh using scaler im
BitmapHandler::doTransform: called wfMkdirParents(/tmp)
BitmapHandler::getMagickVersion: Running convert -version
wfShellExec: /bin/bash '/var/www/mediawiki-1.21.2/includes/limit.sh' ''\''/usr/local/bin/convert'\'' -version' 'MW_CPU_LIMIT=180; MW_CGROUP='\'''\''; MW_MEM_LIMIT=202400; MW_FILE_SIZE_LIMIT=102400; MW_WALL_CLOCK_LIMIT=180'
BitmapHandler::transformImageMagick: running ImageMagick: '/usr/local/bin/convert' -quality 80 -background white -define jpeg:size=112x120 '' -thumbnail '112x120!' -depth 8 -sharpen '0x0.4' -rotate -0 '/tmp/s3thumb-cripEh' 2>&1
wfShellExec: /bin/bash '/var/www/mediawiki-1.21.2/includes/limit.sh' 'OMP_NUM_THREADS='\''1'\'' '\''/usr/local/bin/convert'\'' -quality 80 -background white -define jpeg:size=112x120 '\'''\'' -thumbnail '\''112x120!'\'' -depth 8 -sharpen '\''0x0.4'\'' -rotate -0 '\''/tmp/s3thumb-cripEh'\'' 2>&1' 'MW_CPU_LIMIT=180; MW_CGROUP='\'''\''; MW_MEM_LIMIT=202400; MW_FILE_SIZE_LIMIT=102400; MW_WALL_CLOCK_LIMIT=180'
[thumbnail] thumbnail failed on ip-10-168-26-167: error 1 "convert: no decode delegate for this image format `/tmp/magick-11924QG1rRXzT948I' # error/constitute.c/ReadImage/552.
convert: no images defined `/tmp/s3thumb-cripEh' # error/convert.c/ConvertImageCommand/3127." from "'/usr/local/bin/convert' -quality 80 -background white -define jpeg:size=112x120 '' -thumbnail '112x120!' -depth 8 -sharpen '0x0.4' -rotate -0 '/tmp/s3thumb-cripEh' 2>&1"
LocalS3File::transform thumb:
LocalS3File::transform thumbTempPath: /tmp/s3thumb-cripEh, dest: wiki-images/thumb/1/19/5ovrDaU.jpg/112px-5ovrDaU.jpg
info:1
LocalS3File::transform return thumb: MediaTransformError Object
(
[htmlMsg] => Error creating thumbnail: convert: no decode delegate for this image format `/tmp/magick-11924QG1rRXzT948I' # error/constitute.c/ReadImage/552.<br />
convert: no images defined `/tmp/s3thumb-cripEh' # error/convert.c/ConvertImageCommand/3127.<br />
[textMsg] => Error creating thumbnail: convert: no decode delegate for this image format `/tmp/magick-11924QG1rRXzT948I' # error/constitute.c/ReadImage/552.<br />
convert: no images defined `/tmp/s3thumb-cripEh' # error/convert.c/ConvertImageCommand/3127.<br />
[width] => 112
[height] => 120
[url] =>
[path] =>
[file] =>
[page] =>
[responsiveUrls] => Array
(
)
[storagePath:protected] =>
)
Tried from the command line, copy pasted the command from the log (but used a test file):
convert -quality 80 -background white -define jpeg:size=112x120 '' -thumbnail '112x120!' -depth 8 -sharpen '0x0.4' -rotate -0 'logo.jpg'
but the process hangs. If I run:
sudo convert logo.png -quality 80 -background white -define jpeg:size=112x120 -thumbnail '112x120!' -depth 8 -sharpen '0x0.4' -rotate -0 logo.jpg
It works.
If I check DELEGATES, I have:
DELEGATES jng jp2 jpeg png ps tiff xml zlib
I tried increasing the default memory on media wiki to
$wgMaxShellMemory = 202400;
I feel like I've tried anything. Any ideas?
EDIT:
This is what I've discovered so far:
I'm pretty sure the shell wasn't executing the ImageMagick command because of the escaped backslashes in :
wfShellExec: /bin/bash '/var/www/mediawiki-1.21.2/includes/limit.sh' ''\''/usr/local/bin/convert'\'' -version' 'MW_CPU_LIMIT=180; MW_CGROUP='\'''\''; MW_MEM_LIMIT=202400; MW_FILE_SIZE_LIMIT=102400; MW_WALL_CLOCK_LIMIT=180'
Those ''\'' are causing the command to not run, and hence the "no decode" error. It can't decode, because the file is not there. I've traced wfShellEec to GlobalFunctions.php. The wfShellExec function is at around line 2778 on my file.
In the if ( php_uname( 's' ) == 'Linux' ) block there is:
escapeshellarg( $cmd )
I removed the escapeshellarg() function and just left the $cmd on its own.
Tried uploading again, the error is gone, the files are created, but now the thumbnail files are 0 bytes.
Any ideas?

Answer 1

In the following, the empty string parameter '' represents what is supposed to be the input image:
convert -quality 80 -background white -define jpeg:size=112x120 '' -thumbnail '112x120!' -depth 8 -sharpen '0x0.4' -rotate -0 'logo.jpg'
When you ran sudo convert logo.png ... from the command line it worked because you had an input image (logo.png), but inside MW the source image parameter was missing. So the problem here is not with convert, ImageMagick naturally cannot convert an image that doesn't exist. The problem is that MW fails to supply the source image file name.
If your case is like mine, the empty '' image source parameter could trace back to permissions in the images directory. Make sure this directory and all its subdirectories are rwx by the server process. Once I opened up everything in this dir to the server, the errors went away and the images and thumbnails appeared perfectly.