iOS截图 ,图片合成，画纯色UIimage

1、截取部分UIImage

-(UIImage *)clipImageFromImage:(UIImage *)orgImage  Rect:(CGRect)clipRect{
CGImageRef imageRef = orgImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, clipRect);
CGSize size;
size = clipRect.size;
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, clipRect, subImageRef);
UIImage* clipImage = [UIImage imageWithCGImage:subImageRef];
CGImageRelease(subImageRef);
UIGraphicsEndImageContext();
return clipImage;
}

- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {
UIGraphicsBeginImageContext(image1.size);
[image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];
[image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultingImage;
}

CGSize imageSize = CGSizeMake(50, 50);
UIGraphicsBeginImageContextWithOptions(imageSize, 0, [UIScreen mainScreen].scale);
[[UIColor colorWithRed:0 green:0 blue:0 alpha:1.0] set];
UIRectFill(CGRectMake(0, 0, imageSize.width, imageSize.height));
UIImage *pressedColorImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();