Commands Used with the IMGCTRL, IMGOP and PICFILL Functions |
Dithers an image to a color map
rc=IMGOP(task-id, 'DITHER'<,
option>);
|
region-id=PICFILL(graphenv-id, type, ulr, ulc,
lrr, lrc, source<, 'DITHER'<, arguments>>);
|
- option
-
specifies which color searching algorithm to use. Each algorithm
searches the color map at a different speed. You can specify FS_NORMAL, FS_FAST,
FS_FASTER, or FS_FASTEST. If you specify FS_NORMAL, then SCL exhaustively
searches the color map for the closest match. FS_FAST, FS_FASTER, and FS_FASTEST
each use a progressively faster searching algorithm. These algorithms will
find a close color match but not the closest. Usually, a close match is sufficient.
The faster the search, the less accurate the color match might be. The default
option is FS_FASTEST.
DITHER acts on the currently selected
image. It dithers an image to the current color map: the one specified by
a previous GENERATE_CMAP, STANDARD_CMAP, or GRAB_CMAP command.
Like the MAP_COLORS command, DITHER reduces the number
of colors in an image. Unlike the MAP_COLORS command, DITHER attempts to choose
colors by looking at pixels in groups, not as single pixels, and tries to
choose groups that will result in the appropriate color. This is similar
to the half-toning algorithm that print vendors use to show multiple colors
with the use of only four ink colors. This command is much more computationally
expensive than the other color-reduction commands, but it handles continuous-tone
images much better.
Dither an image:
if (dither=1) then
do;
rc=imgop(task-id,'GENERATE_CMAP','COLORRAMP',
5,5,4);
rc=imgop(task-id,'DITHER');
rc=imgop(task-id,'PASTE');
end;
Copyright © 2009 by SAS Institute Inc., Cary, NC, USA. All rights reserved.