Limit type and size of image previews

MindTouch uses ImageMagick to create thumbnails from uploaded images. To be thumbnailed, an attachment must be smaller than the size defined by

files/imagemagick-max-size 

By default this is: "268435456" (2.5MB)

The attachment must also have a file extension listed in

files/imagemagick-extensions 

By default this is: "bmp, jpg, jpeg, png, gif, tiff"

You made edit these values by going to Control Panel -> Configuration. 

Note: The configuration screen is introduced in MindTouch 1.8.2 (Hayes+). For previous versions, you'll need to make a direct database update into the config table and restart the application.