Comments on: All about pixel colors: Scaled indexed images

By: Steve

Steve — Fri, 24 Jul 2009 00:48:37 +0000

Ilan—Try my imoverview function on the MATLAB Central File Exchange. Compute the mask using something like this:

bw = abs(A - 1.2) <= tolerance;

By: Ilan

Ilan — Wed, 22 Jul 2009 07:12:16 +0000

Hi Steve,

I have a gray image (values ranging from 0 to 5) and I want to color pixels which have certain value (say 1.2).

How can I do that?

Hope you can help.

Thanks,

Ilan

By: Steve

Steve — Fri, 19 Sep 2008 11:39:21 +0000

Greg—I don’t understand your question. Which pixels? Highlight them how? And how is highlighting related to getting the average?

By: Greg

Greg — Fri, 19 Sep 2008 03:55:51 +0000

Now what if you wanted take that original imagesc(A) and highlight a few differnt pixels to get the average related to the original array [A]? Thanks!

By: Steve

Steve — Wed, 16 Apr 2008 17:42:32 +0000

Alex—The default colormap length returned by hot has only 64 colors, so it doesn't make sense to use it to display a 16-bit image with values that go from 0 to 1500. When I try that, I get an image that's all white, which is what I would expect. You might have better luck with something like this:

% Display using the autoscaling syntax of imshow
imshow(I, [])

% Crop
[ROI,rect] = imcrop;

By: Alex

Alex — Wed, 02 Apr 2008 19:27:35 +0000

Dear Steve,
Why am I having trouble using the imcrop function with a scaled image? Or, rather, why does the image not appear scaled anymore when I try to do imcrop on it? I have 16bit TIFF files with values that go from 0 to like 1500. I can use the imagesc function to display them just fine. But what I want to do then is to create regions of interest on such a scaled image. I was trying to use imcrop, but as soon as I put in [ROI,rect] = imcrop(I,hot); the scaled image that was on the screen is replaced by a solid black rectangle. Why is this, and how do I make it work how I want?
Thank you if you can help!

By: Steve

Steve — Wed, 09 Jan 2008 16:23:08 +0000

Smita—When you converted your color image to gray, you discarded information. You can’t get it back.

By: smita

smita — Wed, 09 Jan 2008 07:05:33 +0000

Hi,
steve we are taking a color image converting it into gray image then wavelet transform is going to apply on that gray image.my question to you is can we recover original color image from that wavelet aplplied gray image.
Thank you.

By: Steve

Steve — Tue, 02 Oct 2007 23:22:09 +0000

Sridharan—When imshow displays a grayscale image, it installs a gray colormap in the figure. In your second call to imshow, it replaced the figure’s gray colormap with your label_color colormap. That’s why your gray image starts to look pink. A figure can only have one colormap active at a time. I suggest that you convert your images to truecolor in order to get the desired effect.

By: Sridharan

Sridharan — Fri, 28 Sep 2007 02:00:28 +0000

Hi Steve,

Have a look at the following code. I have an image (apple.bmp) which is grayscale. I want to display an indexed image on top of it with a transparency value associated to it. But i get some weird pink areas on my image. Could you please let me know why this is happening??

label_color(1,:)=[0 0 0];
label_color(2,:)=[1 0 0];
label_color(3,:)=[0 1 0];
label_color(4,:)=[0 0 1];
label_color(5,:)=[1 1 0];
label_color(6,:)=[0 1 1];
label_color(7,:)=[1 0 1];

a1=imread(’apple.bmp’);

d_label=zeros(368,400);
d_label(100:200,100:200)=1;
mask=zeros(368,400);
index1=find(d_label~=0);
mask(index1)=.3;
figure,imshow(a1,[]),hold on
h=imshow(uint8(d_label),label_color);
set(h,’Alphadata’,mask)