loading images opencl

Anybody knows how to load an image in opencl in correctly way ?
I have 512x512 RGB 8bit/channel bmp image. I don’t know how to load it that it would be an argument to the clCreateImage2D as void *host_ptr. I am begginner and my kernel is very simple, it copies input to the output. As a result it returns an image but it is always black. Till now I have used opencv to load an image.
Thanks for a help.