MATLAB: Enhance grayscale image using normalization factor

Question

sir,

I have a gray scale image in the range {0,1}.I want to enhance this gray scale image using normalization factor alpha in order to transform the range from [0.15-0.4] to

[0-0.4]

ie, the pixel values of enhanced gray scale image should be,

fr(x,y)={ 0; if fg(x,y)<=0.15

alpha * fg(x,y) ; if 0.15<fg(x,y)<= 0.4

fg(x,y) ; else } Where fg(x,y) is the gray scale image in the range{0,1}

Answer 1

Try this

img = rgb2gray(im2double(imread('pears.png')));
img(img<0) = 0;
mask = (0.15<=img)&(img<=0.4);
img(mask) = interp1([0.15 0.4], [0 0.4], img(mask));