Hello,
I would like to do an equal area colour distribution using a blue to red
color map. The default color map is fine, but seems to be linear.
Can someone please explain how to apply a equal area colour distribution?
Thanks
Marc Pelletier
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At 10:09 AM +0000 12/3/99, Marc Pelletier wrote:
Hello,
I would like to do an equal area colour distribution using a blue to red
color map. The default color map is fine, but seems to be linear.
There's a nice concise description in Ballard and Brown's book "Computer Vision". The computer graphics literature refers to the technique as histogram equalization.
You need to keep track of two histograms. One is the hist of values in your original image layer. The other is the histogram of color indices in your displayed image. Since you know the size of your layer, you know how many pixels (or areal units of your choice) are in the image. Just divide number of pixels in the image by number of color levels.
Build your color transformation map from lowest to highest value of the original image. Keep a running total of how many pixels are represented by the current output value.
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Mobile Geographics LLC
Seattle, Washington (206) 297-9575