Häufig erhielten wir die Nachfrage GM in Typo3 zu aktivieren, sodass darüber z.B. auch Thumbnails korrekt generiert werden.

Die Einrichtung von GM erfolgt nicht über die Config.php Datei,
sondern direkt über die T3lib Configuration im Pfad:

/t3lib/config_default.php

folgende Einstellungen verwenden:

$TYPO3_CONF_VARS = Array(
'GFX' => array( // Configuration of the image processing features in TYPO3. 'IM' and 'GD' are short for ImageMagick and GD library respectively.
'image_processing' => 1, // Boolean. Enables image processing features. Disabling this means NO image processing with either GD or IM!
'thumbnails' => 1, // Boolean. Enables the use of thumbnails in the backend interface. Thumbnails are generated by IM/partly GD in the file typo3/thumbs.php
'thumbnails_png' => 1, // Bits. Bit0: If set, thumbnails from non-jpegs will be 'png', otherwise 'gif' (0=gif/1=png). Bit1: Even JPG's will be converted to png or gif (2=gif/3=png)
'noIconProc' => 1, // Boolean. If true, icons are never processed with overlays for hidden, starttime, endtime etc. They must be available pre-processed. If this is disabled, do so only if you have full image processing capabilities on the server for TYPO3.
'gif_compress' => 1, // Boolean. Enables the use of the t3lib_div::gif_compress() workaround function for compressing giffiles made with GD or IM, which probably use only RLE or no compression at all.
'imagefile_ext' => 'gif,jpg,jpeg,tif,bmp,pcx,tga,png,pdf,ai', // Commalist of file extensions perceived as images by TYPO3. List should be set to 'gif,png,jpeg,jpg' if IM is not available. Lowercase and no spaces between!

'gdlib' => 1, // Boolean. Enables the use of GD.
'gdlib_png' => 0, // Boolean. Enables the use of GD, with PNG only. This means that all items normally generated as gif-files will be png-files instead!
'gdlib_2' => 1, // String/Boolean. Set this if you are using the new GDlib 2.0.1+. If you don't set this flag and still use GDlib2, you might encounter strange behaviours like black images etc. This feature might take effect only if ImageMagick is installed and working as well! You can also use the value "no_imagecopyresized_fix" - in that case it will NOT try to fix a known issue where "imagecopyresized" does not work correctly.

'im' => 0, // Boolean. Enables the use of IM.
'im_path' => '/usr/bin/', // Path to the IM tools 'convert', 'combine', 'identify'. Version 4.2.9 of ImageMagick is highly recommended due to features and speed!
'im_path_lzw' => '/usr/bin/', // Path to the IM tool 'convert' with LZW enabled! See 'gif_compress'. If your version 4.2.9 of ImageMagick is compiled with LZW you may leave this field blank AND disable the flag 'gif_compress'! Tip: You can call LZW 'convert' with a prefix like 'myver_convert' by setting this path with it, eg. '/usr/bin/myver_' instead of just '/usr/bin/'.

'im_version_5' => '', // String. Set this if you're using ImageMagick/GraphicsMagick but not IM 4.x. Setting this value will automatically configure some settings for use with the specified program version. Allowed values are: "im4", "im5", "im6" and "gm" (uses GraphicsMagick instead of ImageMagick).
'im_negate_mask' => 0, // Boolean. Indicates if the mask images should be inverted first. This depends of the ImageMagick version. Below ver. 5.1 this should be false. Above ImageMagick version 5.2+ it should be true. Just set the flag if the masks works opposite the intension!
'im_imvMaskState' => 0, // Boolean. If set, the 'im_negate_mask' state is inverted. This is very useful with newer versions of IM5 (at least 5.4.3+) where the 'im_version_5' setting will set 'im_negate_mask' which will eventually be wrong... Halleluja for ImageMagick - have I ever regreted using that package...
'im_no_effects' => 0, // Boolean. This is necessary if using ImageMagick 5+. Approved version for using effects is version 4.2.9. Effects in Imagemagick 5+ tends to render very slowly! Therefore this must be disabled in order not to perform sharpen, blurring and such. (However lately IM5 is allowed for effects again, but syntax has changed!)
'im_v5effects' => 0, // Integer -1,0,1. 0=disabled. -1=Do not sharpen images by default. 1=All; blur and sharpening is allowed in ImageMagick again and the 'im_no_effects' flag is cancelled. Blurring and sharpening has new syntaxes though. See class.t3lib_stdgraphic.php for details.
'im_mask_temp_ext_gif' => 0, // Boolean. This should be set if ImageMagick is version 5+. This is used in class.tslib_content.php for masking images and the extension png is normally used because it's faster than gif for temporary files. But png seems not to work with some IM 5+ versions, so...
'im_mask_temp_ext_noloss' => 'miff', // String. Loss-less ImageMagick extension to use for mask processing in temporary filenames. Normally 'miff' (ImageMagick's OWN format) will do fine. However at least IM 5.4.9 has proved not to be able to write to its own file format which forced me to add this option. You can try and set this to tif/png/jpg if some masking doesn't work the way it should.
'im_noScaleUp' => 0, // Boolean. If set, images are not being scaled up if told so (in t3lib/stdgraphics.php)
'im_combine_filename' => 'combine', // String. Latest ImageMagick versions has changed the name of combine to composite. Configure here if needed.
'im_noFramePrepended' => 0, // Boolean. If set, the [x] frame indicator is NOT prepended to filenames in stdgraphic. Some IM5+ version didn't work at all with the typical [0]-prefix, which allow multipage pdf's and animated gif's to be scaled only for the first frame/page and that seriously cuts down rendering time. Set this flag only if your ImageMagick version cannot find the files. Notice that changing this flag causes temporary filenames to change, thus the server will begin scaling images again which were previously cached.
'jpg_quality' => 70, // Integer. Default JPEG generation quality
'enable_typo3temp_db_tracking' => 0, // Boolean. If set, then all files in typo3temp will be logged in a database table. In addition to being a log of the files with original filenames, it also serves to secure that the same image is not rendered simultaneously by two different processes.
'TTFLocaleConv' => '', // String. Enter locale conversion string used to recode input to TrueType functions. Eg. 'cp1250..UTF-8'. Works ONLY if 'recode' is enabled in PHP. Deprecated from ver. 3.6.0 of TYPO3. Set up [BE][forceCharset] as strings are automatically converted from databsae charset to UTF-8.
'TTFdpi' => '72', // Integer. Enter how many dpi the FreeType module uses. Freetype1 should be set to 72. Freetype2 should be set to 96 (otherwise fonts are rendered way bigger than FreeType1). This works as a global scaling factor for Freetype.
'png_truecolor' => 0, // Boolean. If set PNGs will get created as truecolor PNGs. If you use GDlib2 you can create truecolor images if they look not well currently. Note that this results in an increased image size. JPEGs get always created in truecolor now (GDlib2 required)
),