hi,im trying toget the images of L,a,b of CIELab but when i make thetransformation from srgbtolab iget the images ingrayscale,L must be gray-scale color but A shouldbe redness to greenness and b yellowness to blueness. what code i canuse to get this?

If i imread a picture ex,

%load rgb image
src = 'patio.jpg';
rgbI = imread(src);

%convert to lab
labTransformation = makecform('srgb2lab');
labI = applycform(rgbI,labTransformation);

%seperate l,a,b
l = labI(:,:,1);
a = labI(:,:,2);
b = labI(:,:,3);

figure, imshow(l) , title('l');
figure, imshow(a) , title('a');
figure, imshow(b) , title('b');

i get the a and b images in grayscale but i would like to get them, A from redness to greenness and b from yellowness to blueness, all this in terms of color. is it that possible? please help me with the code and dont know what else to do to achieve this.

Answer 1

[Image Analyst]

Yes it's possible. In fact you did it. You're done. a represents the redness/greenness and b represents the yellowness/blueness. You can display them however you want - in gray scale or in some custom colormap, but it's not necessary. In fact it could be somewhat deceptive, like if you displayed high a values in red then you might think those pixels should be red but they might be yellow or they might be purple. Both red and purple have high a values, it's not just red that has a high a value. Plus the color depends on the L value as you'll see from the attached demo (thanks to Jeff Mather of the Image Processing Team at the Mathworks).