Comments on: All about pixel colors: Truecolor and indexed images

By: Steve

Steve — Wed, 13 May 2009 23:19:29 +0000

Imen—Use makecform and applycform for converting between RGB and LAB. I don't understand your question about regionprops; that function is for computing geometric measurements of image regions.

By: imen

imen — Wed, 13 May 2009 22:11:09 +0000

hi my problem is how to create a function to convert an image RGB to XYZ then XYZ to LAB and make it “executable” it means i can run it and see the result
and i have another problem ich is how to create a nother function for searching an image using the commande regionprops????
i hope i will get an answer from you

By: Steve

Steve — Wed, 15 Oct 2008 19:53:06 +0000

Anurag—Here’s a sample:

RGB = imread('peppers.png');
imshow(RGB)
I = rgb2gray(RGB);
figure, imshow(I)
imwrite(I, peppers_gray.png')

By: Anurag

Anurag — Mon, 13 Oct 2008 10:51:21 +0000

hello steve. i need some help in converting true color images to 8-bit grayscale i tried the function rgb2gray but it did not help/ guide me please.

By: Steve

Steve — Tue, 27 May 2008 12:33:42 +0000

Liya—I can’t help you with debugging your code. You might consider posting a note to the MATLAB newsgroup, comp.soft-sys.matlab. If you do, you’ll need to give a more specific description of your problem, because “it’s not displaying” is too vague.

By: liya

liya — Mon, 26 May 2008 02:14:00 +0000

Hello Steve,
thanks for the reply, I tried to use ycbcr2rgb, but I was not able get the true colors, actually I am trying to perform wavelet transform on the color images, I tried to use the for loop for RGB and than concatenate, but I was not able to get it,I dont whats the problem, please help.

for k=1:3
B1=image(:,:,k);
[ca,ch,cv,cd]=dwt2(B1,’wname’);
……
…
decimage(:,:,i)=[ca1r ch1r;cv1r cd1r];
end
decimage1=cat(3,decimage(:,:,1),decimage(:,:,2),decimage(:,:,3));
imview(decimage1)

I tried this way also, but Its not displaying.pls help

By: Steve

Steve — Sat, 24 May 2008 12:10:00 +0000

Iiya—Use ycbcr2rgb.

By: liya

liya — Fri, 23 May 2008 18:08:46 +0000

Hello Steve,
I am working on color images but, i am facing the problem in converting the Ycbcr back to true colors, is there any method ,please help
A=double(I1);
X1rgb=0.2990*A(:,:,1)+0.5870*A(:,:,2)+0.1140*A(:,:,3);

By: Steve

Steve — Tue, 22 Apr 2008 11:35:32 +0000

Darshan—You can’t. When you converted the image to grayscale, you threw the color information away. You can’t get it back.

By: Darshan

Darshan — Tue, 22 Apr 2008 06:22:27 +0000

Resepect sir,
I am very happy for ur kind reply. My aim is to convert first an rgb image to grascale and vice-versa for that i have written the following code as below,
like
I=imread(’flowers.tif’);
figure;image(I);
k=rgb2gray(I);
figure;image(k);
rgb=cat(3,k,k,k);
figure;image(rgb);

but i couldn’t get the colored image. why? if u have any other idea’s plz help me.