This ColdFusion component creates black/white and color image histograms. The component will return histogram array(s) or will write PNG images of the histogram. View the project page for more details and to download the CFC and examples.

Unlike my last example of how to create a histogram, this CFC uses standard Java API currently available to ColdFusion and has no need for external libraries.

To give a brief outline of how this component works for a 3 color histogram

• JPG image is buffered (jpegCodec - decodeAsBufferedImage)
• A holder array[3][256] is created to hold R-G-B values
• Each pixel of image data is looped over (bufferedJPG.getRaster().getDataBuffer().getData())
• The hex value of each (R, G, and B) pixel value is separated. example for red: BitSHRN(bitAnd(p, InputBaseN("ff0000",16)),16)
• As each pixel is looped over the separated RBG values are incremented in the appropriate array cell
• Once the histogram array has been populated an PNG histogram graph image is drawn (using java.awt.Graphics2D)
• For each of the three colors in the array a line is drawn from 0-255 and the height is determined by the value of that array cell

A color histogram is a representation of an image derived by counting the 'color' of each pixel. So while this CFC makes neat looking graphs it also creates an array of the colors so you can determine the frequency of colors in an image.

This CFC is very beta, please read the CFHistogram project page for more details. If you have comments, suggestions, or better ways to do this please let me know.