Face-Based Luminance Matching: lumMakeMap.tcl

This is the second (and more complicated) step in creating colormaps. This program requires an input text file, called "mapin.txt", which describes the colors of the control points that you'd like to start with. The file that comes with lumFace is for a rainbow colormap: 

1 0.02 0.02
1 1 0.02
0.02 1 0.02
0.02 1 1
0.02 0.02 1
1 0.02 1
There is one RGB triple per line, and the values range from 0.0 to 1.0. The reason for not using 0.0 values is that it avoids visual discontinuities when the colors are interpolated, but this is basically a hack. In any case, you need to create a different file with the control points you'd like to use, and save it in a file named exactly "mapin.txt".

lumMakeMap.tcl will read in this file when it starts up. This program is basically a gadget for going through the control points in your mapin.txt, and adjusting their HLS lightness so that they match a pattern of grayscale variation. As with the previous programs, you control HLS lightness either by clicking and dragging inside the image, or by dragging the "Color Level" slider. The gray levels that you match against are controlled by the "Start Level" and "End Level" sliders. These both start at 0.6 by default, but you can make them go from, say, 0.2 to 1.0 for a monotonically increasing colormap. You can also experiment with different images: faces and non-faces.

The "Colormap Index" slider allows you to go through the control points from the mapin.txt. It has only integral values. The program remembers which values you chose for the various colors, and often it is helpful to go back through the control points to see if you still think that the colors are matched with the grays. Once you're satisfied with the levels you've set, click on "Save", then "Quit. Clicking on "Save" will create the "mapout.txt" file which will be processed by the genMaps.txt script. This contains the RGB values of the original colors, but with the adjustments to HLS lightness which you've made by matching faces.

This is the normal operation of the program. Just for fun, though, you can also preview the continuous colormap by moving the "Colormap Position" slider. This does smooth interpolation through the control points to produce all the intermediate colors you'll see in the colormap. In order to do so, however, it needs to know the gamma, which you set by the "Gamma" slider. Currently, you have to remember the value you found by running lumGamma.tcl. If the gamma is set correctly, the faces should balance not just at the control points, but at every position in between. You can see the effect of setting gamma incorrectly by moving the "Gamma" to far high or low. This will cause the faces to be out of balance at all the colors interpolated between control points.