CE OD - Contrast Enhancement - adjust Optical Densities

(07/11/97)

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

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