First you need to grab some memory:
clip=malloc(width*height);
Then you need to set the clip size:
SetClipRect(0,0,width-1,height-1);

Now, you need to set the render destination to your clip above, load an image to a separate buffer, and copysprite and draw the image. This will draw it to your clip. The trick is if your clip starts at 0,0 (as above) and you want to see the 10,10 as the beginning of the image, you need to copysprite to 0-10,0-10. Get it?

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