Adjusting brightness and contrast for indexed images

Question

I am changing the image brightness for an indexed image in MATLAB. For that I created m, a 3x256 ones matrix, then I multiply it with a number, then I add m to x (the map for my image). My question now how to return one if the result is bigger than one.

[im3,x]=imread('corn.tif');
m=ones(256,3)
m=m.*50
[im33 c]=deal(im3,x+m) 

Answer 1

Setting values in the array x larger than the value a to a is variously called clamping, clipping or saturating. The simplest method is using min:

x = min(x,a);

For example, given your color map x:

[im3,x] = imread('corn.tif');

subplot(1,2,1)
imshow(im3,x)

x = x + 0.2;
x = min(x,1);

subplot(1,2,2)
imshow(im3,x)