## How can i color the pixels in red?

### Pamela Paolo (view profile)

on 5 Dec 2012

Hi, for an image I, I want to color in red the pixels having the coordinates x and y stored in the matrix xy

```[L C]=size(I);
xy=[x y];
```

Walter Roberson

### Walter Roberson (view profile)

on 5 Dec 2012

What kind of image is it? RGB or pseudocolor? If it is pseudocolor is it acceptable that it be converted to RGB using the current colormap ?

## Products

### Image Analyst (view profile)

on 5 Dec 2012

Try this, assuming you want to set pixels in an RGB image to red.

```for k = 1 : length(xy)
row = int32(xy(k,1));
col = int32(xy(k,2));
rgbImage(row, col, 1) = 255;
rgbImage(row, col, 2) = 0;
rgbImage(row, col, 3) = 0;
end
```

If you have a monochrome image, you'll first have to convert it to an rgb image:

```rgbImage = cat(3, grayImage, grayImage, grayImage);
% After that, then it's the same loop as above.
for k = 1 : length(xy)
row = int32(xy(k,1));
col = int32(xy(k,2));
rgbImage(row, col, 1) = 255;
rgbImage(row, col, 2) = 0;
rgbImage(row, col, 3) = 0;
end
```

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