https://github.com/Shinmera/trivial-thumbnail.git
git clone 'https://github.com/Shinmera/trivial-thumbnail.git'
(ql:quickload :trivial-thumbnail)
A tiny library to create thumbnails with ImageMagick. The binaries convert and mogrify need to be available on your system for this to work.
The main function to use is create.
(thumbnail:create #p"~/input.png" #p"~/input-thumb.png")
=> #p"~/input-thumb.png"
Of course it allows for different kinds of thumbnail generation with the crop argument:
(thumbnail:create #p"~/input.png" #p"~/input-thumb.png" :crop :WIDTH)
(thumbnail:create #p"~/input.png" #p"~/input-thumb.png" :crop :HEIGHT)
(thumbnail:create #p"~/input.png" #p"~/input-thumb.png" :crop T)
Using :WIDTH means that the image is first scaled down preserving the aspect ratio to fit into the given height and then crops the remaining width to fit the given width. :HEIGHT works similarly. T just crops the image without any scaling.
This library uses ImageMagick mostly because it can handle gif animations properly, which a lot of other tools cannot. Processing animation is calculation-intensive though, so if you want to disable that (resulting in a static gif), you can pass :preserve-gif NIL.
Trivial-Thumbnail attempts to locate the necessary binaries automatically, searching the usual paths such as /usr/bin, /usr/local/bin and C:/windows/system32/, C:/Program Files/ImageMagick*/. If it fails to find a suitable binary, it throws a warning at startup. When the binary is somewhere else, but still within your PATH, it should still work properly. Otherwise you will have to set *CONVERT-BIN* and *MOGRIFY-BIN* yourself.