Question: How are tif-files stored?
Answer: A tif-file defines a two-dimensional array of values. Each value is between 0 and 255. "0" represents "pure black" and "255" represents "pure white". Values in between are shades of gray.
For example, if
a = [ 0 0 0 0 0;
0 255 255 255 0;
0 255 165 255 0;
0 255 165 255 0;
0 255 255 255 0;
0 0 0 0 0 ],
then "imagesc(a)" followed by "colormap(gray)"
will display a gray box in a white
box in a black background. (Try it!)
So if we wanted the area of the gray and white boxes, we could create a function that was 1 when a(i,j) was less than 166 and 0 otherwise.
Question: Should we read the image (using imread) everytime we need it?
Answer: No, this is very inefficient. Your program should read it once only. (Otherwise you will lose a point on your grade.)
Question: What happens if we ask Matlab for the matrix element e(x,y) with x=22.4 and y=19.6?
Answer: Matlab will give an error message. The indices x and y used to get a matrix element must be positive integers. Consider using the "round" function.
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