C4 saving part of an image

Question

Hei, I went through the example for saving images and afterwards I wanted to save only a part of the screen. I managed to save the part starting at the upper left corner of the

Answer 1

a little modification to Travis' answer makes it independent from the image but dependent on the canvas origin:

-(C4Image *)cropImage:(C4Image *)originalImage withOrigin:(CGPoint)origin toArea:(CGRect)rect{
    //grab the image scale
    CGFloat scale = originalImage.UIImage.scale;

    //begin an image context
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, scale);

    //create a new context ref
    CGContextRef c = UIGraphicsGetCurrentContext();

    //shift BACKWARDS in both directions because this moves the image
    //the area to crop shifts INTO: (0, 0, rect.size.width, rect.size.height)
    CGContextTranslateCTM(c, origin.x-rect.origin.x, origin.y-rect.origin.y);

    //render the original image into the context
    [originalImage renderInContext:c];

    //grab a UIImage from the context
    UIImage *newUIImage = UIGraphicsGetImageFromCurrentImageContext();

    //end the image context
    UIGraphicsEndImageContext();

    //create a new C4Image
    C4Image *newImage = [C4Image imageWithUIImage:newUIImage];

    //return the new image
    return newImage;
}