how can I draw a grid over a specified region of the image

For example, I have an image of 400*360. I want to draw small grids over a region of the image. E.g. draw small grids of 20*20 started from (50, 60) and until (300, 280). How can I do this?

[ZhG]

fix it already

Answer 1

[Image Analyst]

You can do it in the overlay, with line(),

for row = 50 : 20 : 300
  line([1, 360], [row, row];
end

for column = 60 : 20 : 280
  line([column , column ], [1, 400];
end

or you can burn it into the image like this:

for row = 50 : 20 : 300
  grayImage(row, :) = 255;
end

for column = 60 : 20 : 280
  grayImage(:, column) = 255;
end