how to enhance a color image ?

For gray image, we use the commands like adapthisteq, imadjust... How to increase the intensity for the color image.

Answer 1

[Image Analyst]

Convert to hsv color space with rgb2hsv(). Then do those same things on the v channel, then transform back to rgb color space with hsv2rgb().

[Sivakumaran Chandrasekaran]

I=imread('fog1.bmp'); v=rgb2hsv(I); b=adapthisteq(v); g=hsv2rgb(b); figure,imshow(g) when i run the code, i am getting an error as 3 D images. Does my procedure follows your reply or i gone to a wrong approach

[Sivakumaran Chandrasekaran]

I have a doubt on your reply...can you explain me little bit brief about the line...do those same things on the v channel indicates... Exactly it indicates what?

[Jürgen]

Siva,

take a look at http://en.wikipedia.org/wiki/HSL_and_HSV HSV is a colorspace like rgb , you have three channel , insted of R, G and B, you have H, S and V, a possibility is also to transform to gray scale regardsJ

[Image Analyst]

Your v is the full 3D image with all the h, s, and v channels. Do this:

hsvImage = rgb2hsv(rgbImage);
% Extract individual color channels.
hChannel = hsvImage(:, :, 1);
sChannel = hsvImage(:, :, 2);
vChannel = hsvImage(:, :, 3);
% Do stuff to the v channel.
% Then, after that recombine the new v channel
% with the old, original h and s channels.
hsvImage2 = cat(3, hChannel, sChannel, vChannel);
% Convert back to rgb.
rgbImage2 = hsv2rgb(hsvImage2);

[Sivakumaran Chandrasekaran]

Thanks Image Analyst.. Now, I got your point..

[DGM]

FWIW, the synopsis for adapthisteq() has had an example of doing this in LAB. That said, it's written around very old conventions, so it can be simplified in contemporary versions. For comparison:

inpict = imread('peppers.png');

cl = 0.005;

% adjust V in HSV
hsvpict = rgb2hsv(inpict);
hsvpict(:,:,3) = adapthisteq(hsvpict(:,:,3),'cliplimit',cl); % adjust
op1 = im2uint8(hsv2rgb(hsvpict));

% adjust L in LAB
labpict = rgb2lab(inpict);
labpict(:,:,1) = adapthisteq(labpict(:,:,1)/100,'cliplimit',cl)*100; % adjust
op2 = im2uint8(lab2rgb(labpict));

outpict = [inpict; op1; op2];

imshow(outpict,'border','tight')

... either way, it might not look so great.