Question

I’m working on a C program that crops .ppm files from a starting point pixel (x,y) (top left corner of cropped image) to an end point pixel (x+w,x+h)(bottom left corner of cropped image).

The data in .ppm files is of the following format:

r g b r g b r g b r g b r g b r g b
r g b r g b r g b r g b r g b r g b
r g b r g b r g b r g b r g b r g b
r g b r g b r g b r g b r g b r g b

Is there a simple way, wich avoids the use of 2 dimensional arrays, to do this using scanf()?

Answer 1

One easy way would be to simply keep track of your pixel coordinate as you read the file in. If you’re currently in the crop rectangle, store the pixel; otherwise, skip it.

If you want to get more fancy: figure out the byte offset for the start of each row, seek to it, then read in the whole row.