CE OD - Contrast Enhancement - adjust Optical Densities

PURPOSE

Finds the logarithmic transformation (applied to pixels) which adjusts the histogram of the image file to the normal N(0,1) distribution. Can be used to convert transmission values from a scanner to optical density - the assumption is that pixel values should have normal distributions.

SEE ALSO

CE FIT	[Contrast Enhancement - FIT the histogram]
CE GNC	[Contrast Enhancement - Graduated Non Convex restoration]
CE MED	[Contrast Enhancement - Median Filtering]

USAGE

.OPERATION: CE OD [a],[b],[c]

.INPUT FILE: IMG001
[Enter the name of the image file whose histogram has to be corrected. This file will be overwritten.]

.HISTOGRAM LENGTH: 16
[Enter the length of the histogram. For 8 bits scanner the density range is 0-255, thus 16 is appropriate. For 12 bits scanner use 32.]

NOTES

1. Input file can be either 2D or 3D.

2. The input file should contain the background noise of the micrograph.

3. The transformation is A*(ALOG10(x+B)+C).
   The parameters are returned in the registers:
   A - [a]
   B - [b]
   C - [c]
   

4. Implemented by Paul Penczek.

5. Example:

    
       ; Adjust optical densities to the normal distribution. 
       CE OD [a],[b],[c] 
         pap001 
         32 
       AR 
         pap001 
         _2 
         [a]*(LOG(p1+[b])+[c]) 
       FS 
         _2 
       CP 
         _2 
         pap002 
       EN  
   

SUBROUTINES

HISTOD, HISTODC, FHODT

CALLER

UTIL2