How to process jpg images with c/c++ most easily?

Question

I want to iterate over each pixel color in a jpg format image,

which library should I refer to to do this so that the code can be as short as possible?

Answer 1

I can think of either ImageMagick or CImg. Here is a CImg tutorial for you. They abstract away a lot of the decompression details and just give you a grid to work with.

If you go with CImg, you only need to use the data call. You can probably do something like:

CImg<unsigned char> src("image.jpg");
int width = src.width();
int height = src.height();
unsigned char* ptr = src.data(10,10); // get pointer to pixel @ 10,10
unsigned char pixel = *ptr;

Answer 2

Qt has a QImage class:

QImage i("input.jpg");
int x, y;
for (y = 0; < i.height(); ++y) {
   for (x = 0; x < i.width(); ++x) {
      doSomethingWith(i.pixel(x, y));
   }
}

Answer 3

I would use Allegro Game Library http://liballeg.org/Allegro it's simple / open source / free / multiplatform, and you can iterate pixel by pixel if you want