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]

USAGE

.OPERATION: CE OD,X21,X22,X23

.IMAGE TO CORRECT FILE: IMG001
[Enter the name of the image file which histogram has to be corrected.]

.HISTOGRAM LENGTH: 16
[Enter the length of the histogram. For 8 bits scanner the density range is 0-255, thus 16 is appropriate. For 8 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 - X21
   B - X22
   C - X23
   

4. Memory requirements: input file is kept in the memory.

5. Implemented by Paul Penczek.

6. Example is included at the end.

SUBROUTINES

HISTOD, HISTODC, FHODT

CALLER

UTIL2

 ; Adjust optical densities to the normal distribution.
 CE OD,x21,x22,x23
 pap001
 32
 ar
 pap001
 _2
 x21*(LOG(p1+x22)+x23)
 FS
 _2
 CP
 _2
 pap002
 EN D