imagemagick

Convert image format

$ convert [input.png] [output.jpg]

$ convert [input.jpg] -resize [800x600] [output.jpg]

$ convert [input.jpg] -thumbnail [150x150^] -gravity center -extent [150x150] [thumb.jpg]

$ convert [input.jpg] -gravity south -annotate +0+10 "[Copyright]" [output.jpg]

$ convert [a.jpg] [b.jpg] +append [combined.jpg]

$ convert -delay [100] [*.png] [animation.gif]

$ identify [image.jpg]

convert [options] input [operations] output
identify [options] image
mogrify [options] images

ImageMagick is a suite of tools for image manipulation. It can convert, resize, crop, rotate, combine, and apply effects to images in over 200 formats.
Key tools: convert (transform), identify (info), mogrify (in-place edit), composite (combine), montage (collage).

-resize geometry

Resize image.

Crop image.

Rotate image.

JPEG/PNG quality (1-100).

Anchor point for operations.

Add text annotation.

Apply blur.

Sharpen image.

Convert colorspace.

Set resolution.

Memory-intensive for large images. Security policy may restrict some operations. Syntax can be complex. convert renamed to magick in v7.

ImageMagick was created by John Cristy in 1987 at DuPont. It's been continuously developed and remains the most widely used command-line image processing toolkit.

convert(1), identify(1), mogrify(1), ffmpeg(1)