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;
}

2图片合成：

- (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;
}

 3画纯色UIImage

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();