c# - How to crop huge image

Question

I need to process large images (20,000x20,000pixels) in C#. Opening these images directly isn't the way to go because of memory limitations, but what I want to do is split the image into smaller pieces (cropping). I was looking for a 3rd party library that could the trick, but so far no result. I tried FreeImage and ImageMagick, but they cannot open an 20,000x20x000 pixel image. How can I achieve this?

Answer 1

My current project at work consists of an image viewer/analyzing program capable of loading images in excess of 16 gb. You have to use manual file IO, pull the header information out and create your subimages on-demand (or if you're processing the image, you can create a single tile and process it in-place). Very few libraries are going to give you the capability to load/modify a 20k by 20k image (1.2gb at 24bpp) and the ones that do will rarely do so with anything resembling performance (if that is a concern).