Function

Summary

Returns an external image containing color information from an image.

Signature

externalize-image gp
 image
 &key maximum-colors

                 important-colors
 &allow-other-keys =>
                  external-image

Arguments

gp

A graphics port

image

An image

maximum-colors

An integer or nil

important-colors

An integer or nil

Values

external-image

An external image

Description

The external-image function returns an external image containing color information from image . If maximum-colors is nil , the default value, an external image using all the colors in image is created. If maximum-colors is an integer, the external image containing image will be created using no more than that number of colors. If the image contains more than maximum-colors colors, the maximum-colors most frequently used colors will be accurately stored; the remainder will be approximated by nearest colors out of the accurate ones, using the Color System parameters color::*local-rgb-color-distance-red-weight* and so on as the weighting factors for the color distance. The value of important-color is recorded in the external-image for later use, and specifies the number of colors required to draw a good likeness of the image. The default value is the number of colors in the image.