Masking and Reverse Masking in Imageview ios

问题:

I have one Imageview that contains the Image . And one Mask Shape that contains shape of rabbit. I have one code that gives the below result.

- (UIImage*)mynewmaskImage:(UIImage *)image withMask:(UIImage *)maskImage {
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

CGImageRef maskImageRef = [maskImage CGImage];

// create a bitmap graphics context the size of the image
CGContextRef mainViewContentContext = CGBitmapContextCreate (NULL,320, 380, 8, 0, colorSpace,(CGBitmapInfo) kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorSpace);

if (mainViewContentContext==NULL)
    return NULL;

CGFloat ratio = 0;

ratio = 320/ image.size.width;

if(ratio * image.size.height < 380) {
    ratio = 380/ image.size.height;
}

CGRect rect1  = {{0, 0}, {320,380}};
CGRect rect2  = {{-((image.size.width*ratio)-320)/2 , -((image.size.height*ratio)-380)/2}, {image.size.width*ratio, image.size.height*ratio}};

//  CGContextDrawImage(mainViewContentContext, rect2, image.CGImage);

CGContextClipToMask(mainViewContentContext, rect1, maskImageRef);
CGContextDrawImage(mainViewContentContext, rect2, image.CGImage);
CGImageRef newImage = CGBitmapContextCreateImage(mainViewContentContext);
CGContextRelease(mainViewContentContext);

UIImage *theImage = [UIImage imageWithCGImage:newImage];

CGImageRelease(newImage);

// return the image
return theImage;}

The above code gives this result.

But I want the below result (like reverse masking).

How it is possible.Please Help me. Thanks.

回答1:

You should look through blendMode. Try smth like this:

[rabbitImage drawInRect:rect
              blendMode:kCGBlendModeDestinationOut
                alpha:1.0];