Extension:VipsScaler

The VipsScaler extension is a wrapper around VIPS, a free image processing software. VIPS is a set of image manipulation tools specially designed for speed and low memory usage. This is useful for resizing large PNGs, and it the appearance of shrunken JPEGs.

The extension shells out to the vips binary. It can be configured to scale only certain files (for example: big PNGs) by configuring $wgVipsOptions.

Install VIPS
Install VIPS. It can be downloaded from https://libvips.github.io/libvips or your OS repository (see below).

Debian / Ubuntu
$ apt-get install libvips-tools

If you want to build from source have a look at upstream documentation: https://libvips.github.io/libvips/install.html

(Wikimedia has packaged and uses a more recent version for Ubuntu 12.04 at [ https://wikitech.wikimedia.org/wiki/APT_repository apt.wikimedia.org])

Mac OS X

 * homebrew
 * brew install homebrew/science/vips
 * binary symlink is /usr/local/bin/vips

Configuration

 * $wgVipsCommand : path to the vips command (default: vips).
 * $wgVipsOptions : Options and conditions for images to be scaled with this scaler. Set to an array of arrays. The inner array contains a condition array, which contains a list of conditions that the image should pass for it to be scaled with vips. Conditions are mimeType, minArea , maxArea , minShrinkFactor , maxShrinkFactor . The other items in the array are options. Options available are:
 * sharpen: Set to an array with keys 'radius' and 'sigma', which are parameters to gaussian sharpen matrix.
 * preconvert: Convert the file to a .v file first, which costs some space, but saves memory on the actual downsize
 * bilinear: Use im_resize_linear instead of im_shrink
 * convolution: Apply specified convolution matrix
 * setcomment: Add an exif comment specifying the source of the file. Requires $wgExiv2Command to be set properly.