Create screen background images by compositing a number of variable-sized smaller images to minimise empty space i.e. given a fixed-size target area create composite images by combining smaller images without overlapping.
Also included is a command that generate and install a GNOME background control file that will rotate a set of screen backgrounds randomly.
node bin/collage.js will tell you how to use the image compositor.
node bin/gnome_rotate_wall.js will tell you how to generate and install
the rotating wallpapers.
The algorithm used is derived from Richard E. Korf's paper: "Optimal Rectangle Packing: Initial Results" with modifications to permit overlapping candidate areas to make better use of the variable aspect ratios of input images.
Given a set of input Images, and a set of target Layouts, determine if the image fits into an available space on one of the Layouts and if not, create a new Layout. Each Image is only used once, and is removed from the candidate set for later layouts after being used.
Each Layout has a set of free Space objects representing available spaces. Each free Space defines a rectangular area, and a set of other free spaces that it overlaps. When an image is locked into a free Space it becomes a locked Space and all overlapping free Spaces are deleted. Any unused area of the original space is added to the Layout. Images are placed in a corner of the space they occupy, and new spaces created from the unoccupied borders. Images are not scaled to fit.
When it is looking for a free space for an image, all available free spaces are examined. The best free space to use for an image is determined by a cost function which compares two areas to determine which the image fits best in. Two cost functions are available:
- AREA - the cost is the total of the wasted area
- AXIS - the cost is the minimum of the waste along the X or Y axis
The code is Javascript written for node.js 19.3.0 using (http://www.graphicsmagick.org/)[GraphicsMagick] for image operations.