I want to specify ranges of color, like the pre-defined ones that r.colors uses (such as byr) Applying byr to a map gives a gradient of blue through yellow to red. But I want to specify where the break points occur. I can't use percentages in a user defined file because then r.colors decides based on the total RANGE of colors. I have a set of maps (RADAR) where the total range of values varies from image to image, but each value must be colored the same way across maps (so they look right in a sequence animation). I can't edit the color file manually, because I am trying to automate the processing of thousands of files.
Any ideas? Thanks in advance!
Jason
Jason Horn
Boston University Department of Biology
5 Cumington Street Boston, MA 02891
I want to specify ranges of color, like the pre-defined ones that
r.colors uses (such as byr) Applying byr to a map gives a gradient of
blue through yellow to red. But I want to specify where the break
points occur. I can't use percentages in a user defined file because
then r.colors decides based on the total RANGE of colors. I have a
set of maps (RADAR) where the total range of values varies from image
to image, but each value must be colored the same way across maps (so
they look right in a sequence animation). I can't edit the color file
manually, because I am trying to automate the processing of thousands
of files.
Create a custom color table with r.colors for a representative map (full
range of values), then copy that color map to each subsequent map.
The values you enter into r.colors are absolute, not percentages (unless
you use the % sign).
e.g.
r.colors map=radar_map001 color=rules << EOF
0 black
250 blue
500 yellow
750 red
1000 white
EOF
If you want to use d.legend in the animation, GRASS 5.3+ supports using
the range= option to draw to the extent of the color table, not just
the range of values shown on the map which is the default. Of course
you'd have to use the at= option to draw it in the same place for each
frame.
Have a look at the 'gifsicle' program for creating animated GIFs you can
play back in any web browser, esp. nice in a web browser that does full
screen mode.. http://www.lcdf.org/~eddietwo/gifsicle/