This verifies that your ImageMagick installation is able to read the default
formats jpg, gif, png, tif, pdf and ai. The tool 'identify' is
used to read the pixeldimensions of non-web formats and 'convert' is used to
read the image and convert it to jpg.
Test-Image by Rotkaeppchen68 (in de.wikipedia) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons
In case the images appear remarkably darker than the reference images,
try to set [TYPO3_CONF_VARS][GFX][colorspace] = sRGB.