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Rescale 8-bit grayscale image

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Ben Ma
Ben Ma on 8 Sep 2021
Edited: Ben Ma on 9 Sep 2021
  1. intensity values in the range [0..63] in f become 0,
  2. in the range [63+1..126] are rescaled into the range [0..120],
How to rescale the image? Thanks.

Answers (1)

DGM
DGM on 8 Sep 2021
Edited: DGM on 9 Sep 2021
Here's a start:
inpict = imread('cameraman.tif');
inrange = [64 126; 127 230];
outrange = [0 120; 151 255]; % you sure you don't mean 121?
m = inpict<=inrange(1,2);
outpict = zeros(size(inpict),'uint8');
outpict(m) = (double(inpict(m))-inrange(1,1))./(inrange(1,2)-inrange(1,1)) ...
.*(outrange(1,2)-outrange(1,1))+outrange(1,1);
outpict(~m) = (double(inpict(~m))-inrange(2,1))./(inrange(2,2)-inrange(2,1)) ...
.*(outrange(2,2)-outrange(2,1))+outrange(2,1);
imshow(outpict)
imhist(outpict)
You can do the same using interpolation:
inpict = imread('cameraman.tif');
inrange = [0 64 126 127 230 255];
outrange = [0 0 120 151 255 255];
outpict = uint8(interp1(inrange,outrange,double(inpict),'linear','extrap'));
imshow(outpict)
imhist(outpict)
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