Blurring/Filling in color on jpeg image.

Hi,

I'm working with painmaps (see example attached), and I'm trying to shade in the red areas. As you can see the red is scribbled on and there are white spaces within, I'd like to take the outer extremities of the red scribbling and fill in everything inside of it red, so that it's one solid block of red. This is so that I can quantify the shaded pixels for analytical purposes. Any help with this would be much appreciated. I was thinking that perhaps imfill or morphological closing could be used, but I'm struggling to make either option work.

Thanks, Matt

Answer 1

[Image Analyst]

You need to do some steps like I showed you before to get the red scribbles. Then you need to call activecontour() to get the "envelope" of the red scribbles. See attached demo.

[Matthew Alston]

This seems to be working nicely, thanks! After determining the final contour I want to use imfill to fill in the red area right?

[Image Analyst]

Yes. activecontour gives you a binary image. You can say

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Set image to pure red where binaryImage is true.
redChannel(binaryImage) = 255;
greenChannel(binaryImage) = 0;
blueChannel(binaryImage) = 0;
% Recombine separate color channels into a single, true color RGB image.
rgbImage = cat(3, redChannel, greenChannel, blueChannel);

[Matthew Alston]

Sorry to revisit this topic but I played around with the code you provided a but until I got something that fits my needs, but I still can't figure out how to fill in the area inside of the contour. I provided the original image, the script, and what the image looks like after I run the script.

Also if there's any way to have the contour line come up between the legs to find the contour around the shading of each leg individually (instead of crossing the gap around the calves) that would be great, but less important than filling the contour.

[Image Analyst]

This code doesn't have the code I just gave you, so no wonder it doesn't fill in anything.

To go up between the legs you'd need a body template to multiply the thing by. You can try to align the template to your image, perhaps with imregister though I'm not sure ho well it would work on just a partial body.

[Matthew Alston]

Yes sorry I forgot to explain that I was struggling to get the above code to work. Before I can extract the color channels I need to convert the image to rgb from grayscale right?

I used: rgbImage = cat(3, grayImage, grayImage, grayImage);

Then I extracted each color channel: % Extract the individual red, green, and blue color channels. redChannel = rgbImage(:, :, 1);

greenChannel = rgbImage(:, :, 2);

blueChannel = rgbImage(:, :, 3);

But when I get to this part I get stuck : "% Set image to pure red where binaryImage is true." This is the error message I get:

redChannel (binaryImage) = 255; Undefined function or variable 'binaryImage'.

Could you offer advice to what I'm doing wrong? Sorry I'm a very inexperienced Matlab user. The full code is attached to make it easier to view.