How to know the real row and column indices of a pixel in the image

Hi,

I have an image. See below.

>> fn = 'Unknown.jpg';
>> RGB = imread(fn);
>> whos RGB
  Name        Size                Bytes  Class    Attributes

  RGB       235x214x3            150870  uint8  
  
>> s = size(RGB);
>> RGB = reshape(RGB, s(1)*s(2),3);
>> whos RGB
  Name          Size             Bytes  Class    Attributes

  RGB       50290x3             150870  uint8              

After 'reshape', now 'RGB' becomes 50290 by 3.

I wonder that given a row index such as 37987 in the current form of RGB, how to find the corresponding pixel in the image and eventually draw a circle around that pixel on the image.

The main thing is to find the correspoinding pixel in the image.

I tried. However, the pixel I found is outside that image and is white as [255 255 255] which doesn't seems right at all.

Answer 1

[Walter Roberson]

which_pixel = 37987;

[r, c] = ind2sub([s(1), s(2)], which_pixel);

And remember that row corresponds to Y and column corresponds to X.

[Salad Box]

Fabulous!!!!

It worked perfectly!!! You saved my day!!! Thanks a million!!!