圖片剪裁

- (UIImage *)getClipImage:(UIImage *)sourceImage clipRect:(CGRect)clipRect {

    CGFloat (^rad)(CGFloat) = ^CGFloat(CGFloat deg) {
        return deg / 180.0f * (CGFloat) M_PI;
    };

    CGAffineTransform rectTransform;
    switch (sourceImage.imageOrientation) {
        case UIImageOrientationLeft:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(90)), 0, -sourceImage.size.height);
            break;
        case UIImageOrientationRight:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-90)), -sourceImage.size.width, 0);
            break;
        case UIImageOrientationDown:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-180)), -sourceImage.size.width, -sourceImage.size.height);
            break;
        default:
            rectTransform = CGAffineTransformIdentity;
    };
    rectTransform = CGAffineTransformScale(rectTransform, sourceImage.scale, sourceImage.scale);
    CGRect transformedCropSquare = CGRectApplyAffineTransform(clipRect, rectTransform);

    CGImageRef imageRef = CGImageCreateWithImageInRect(sourceImage.CGImage, transformedCropSquare);
    UIImage *image = [UIImage imageWithCGImage:imageRef scale:sourceImage.scale orientation:sourceImage.imageOrientation];

    return image;
}