resolution: a pointer that will accept the image resolution.
options: bit-coded. If bit0 is set (1), then the returned image is rgba, otherwise it is rgb.
filename: the name of the file to read. The file extension indicates the format. If you wish to load an image from a memory buffer, then have filename point to that memory buffer.
reserved: Set to NULL if you load an image from file. If you load an image from a memory buffer, this should be to an integer pointer where the first pointed integer is the size of the memory buffer.