Imagemagick is a collection of command line tools for images. Images can be converted from one format to an other by using the following command:

convert<input file>.jpg <output file>.png

or resize convert <input file>.gif -resize 50% <output file>.gif

convert is used for copying mogrify is used to modify a file.

identify -verbose <file> prints out information about the picture

mogrify -resize "100x200" <file>.png does not always resize picture to 100x200 since it respects the x/y ratio mogrify -resize "100x200!" <file>.png does it.

The -units parameter is confusing, it is some hight level parameter that tells how the units are shown as a result. It has nothing to do what will be written into the file.

Imagemagick has also a simple gui display where many things as display image properties and meta data can be observed.

Imagemagick can convert vector formats as svg in bitmaps as png.

However for simple resizing svg it is better to use xml operations to change the width and height attributes of its root element and introduce a viewbox attribute.

Imagemagick can also be used to create pictures and attach them together. Automated pictures containing customized text can be created this way. If not everything fits into a single command bash scripts are used.

Imagemagick can also be used to put different pictures together forming animated gifs.

Some links:

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