By Andrew McCombe
May 17, 2013
This morning I had an issue with a PHP imagick ImagickException when converting a PDF/postscript file to a thumbnail. I have PHP Imagick, Imagemagick and Ghostscript installed and everything verifies as OK in phpinfo output. The error is:
ImagickException: no decode delegate for this image format `/' @ error/constitute.c/ReadImage/532
$im = new Imagick("$pdf_filename"); $im->thumbnailImage(150, 220); $im->writeimage($thumbnail);
This is a known bug (see http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=11989) and is fixed in the latest releases. Unfortunately the fixes haven't made it into our server's packages yet (Ubuntu precise64 / PHP Imagick 3.1.0RC2). The fix is to read the file from a file pointer rather than direct.
$pdf_filename = '01.pdf'; $thumbnail = '01.jpg'; $f = fopen($pdf_filename, 'r'); fseek($f, 0); $im = new Imagick(); $im->readimagefile($f); fclose($f); $im = $im->flattenImages(); $im->setcolorspace(imagick::COLORSPACE_RGB); $im->setimageformat('pdf'); $im->thumbnailImage(150, 220); $im->writeimage($thumbnail);
Initially it worked but thumbnails were being generated with black backgounds. Adding the call to “$im->setColorSpace(imagick::COLORSPACE_RGB)” resolved that.
Many thanks to Åsmund Herikstad for posting the solution that led me to the issue at http://www.herikstad.net/2010/05/postscript-delegate-failed-for.html