Question

How is the image data saved with an uint8 array? Say that I have an obscure circular image, instead of a rectangular, so there is no pixel data beyond the circle. How do I go about the top most pixel location? The bottom most? Etc… And this image does not have to be a circle, it could be something obscure and non-geometric.

Answer 1

The image is loaded into an array of rows x columns x RGB.
Assuming missing pixels are zeros, here are the top/bottom/left/right coordinates:

[top_col, top_row]= find(sum(I,3)', 1);
[bottom_col, bottom_row]= find(sum(I,3)', 1, 'last');
[left_row, left_col]= find(sum(I,3), 1);
[right_row, right_col]= find(sum(I,3), 1, 'last');