Highlight Image Differences

After your ``unknown'' gel has been warped (see Sec.8.6.2), you can use Highlight Image Differences to see the areas where spots on the unknown gel are darker or lighter than the reference gel.

1. Specify the image number of the reference gel in the clickbox labeled ``Img 1'' and the image number of the warped unknown gel in the clickbox labeled ``Img 2''.
2. Enter the lower and upper ratios in the boxes.
3. Enter the color to be used if a spot decreases and the color to be used if the spot increases. The numbers to use will depend on the pixel depth of the image (i.e., whether it is an 8, 16, or 24-bit image). The following values are good:

   Bits/pixel	Black	White
   8 grayscale *	0	255
   16 grayscale	0	65535
   24, 32 (color)	0	16777215

   * Do not use 8-bit indexed color for this operation.

Imal will calculate the ratio of the corresponding pixel values in the reference gel divided by the unknown gel. If the ratio is below the Lower Ratio Threshold, that pixel will be set to the color specified in ``Color for decrease''. If the ratio is above the Upper Ratio Threshold, that pixel will be set to the color specified in ``Color for increase''.