How can I take a screenshot and save it as JPEG on Windows?

Question

I\'m trying to find a (somewhat) easy way to take a screenshot on window and save the resulting HBITMAP as a JPEG. The tricky part here is that since the code is in C I can\

Answer 1

Good image compression is hard. There's a reason library code exists for the common formats. It requires a lot of code to do. Your constraints on the problem don't make it sound like there is a practical solution.

There are a couple things to try.

1. Use an 8-bit per pixel BMP rather than a true color BMP. This assumes that the information loss in color mapping is acceptable, of course. It will buy you a factor of three in file size over a 24-bit BMP.

2. Try using run length encoding in the BMP you write. RLE is a documented format for BMP, and there should be plenty of sample code out there to make it. It works best on images that have a lot of long runs of identical color. A typical screen without too many gradients and fills fits that description.

3. If those aren't sufficient, then you might need to resort to a stronger compression. The source code to libjpeg is readily available, and it is possible to statically link it rather than using the DLL. It will require some effort to configure in only the bits you need, but the compression and decompression code are almost completely independent of each other and that splits the library almost in half.