TAPESTRY: The Art of Representation and Abstraction
Pixmap
DEFINITION
A pixmap is a raster data set to which size/resolution information has been appended. This is the mechanism by which most vector-graphics programs operate on raster data.
Note While the concept of a PIXMAP is fairly ubiquitous, the actual term used to describe this concept is not widely standardized in the industry.
EXPLANATION
Strict raster data simply consists of pixel color information in a grid of pixels. There is no inherent size information. On a high-resolution display (hence, one with small pixels), the image would be physically small, while on a low-reolution display (with coorespondingly large pixels), the image would be physically large.
By associating a resolution or a size with the raster data, it is possible to treat the raster data set as a whole as if it were attached to a rectangle, or "postcard", almost as it were a non-repeating fill pattern. This allows it to be displayed at the "correct" size when it is one of several other objects in the composition.
OPERATION
The raster data is read into the program, along with the size information. The size data provides a context within which to display the raster data. After taking position, zooming and scaling issues into account, the rectangle is drawn, and then filled with the raster image (the image will likely need additional processing to fit it to the screen pixels).
BENEFITS
Raster data can be integrated into an object graphic environment. A high resolution raster image may be composed on a relatively low resolution display, and yet be printed at the higher resolution of the data (since printers are usually higher resolution than screens).
Last updated: April, 2014
