如何用ios中的圖像遮罩圖像？

我有一個正方形的圖像，代表一個由白色圍成的厚圓圈，另一個正方形圖像代表一張臉。我想用圓圈掩蓋第二張圖像，以便最終圖像是第二張圖像的臉部帶有瑕疵的粗圓。目標c如何實現？如何用ios中的圖像遮罩圖像？

2014-07-09 Sasha Grievus

最後我使用該功能

+ (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage 
{ 
    CGImageRef imgRef = [image CGImage]; 
    CGImageRef maskRef = [maskImage CGImage]; 
    CGImageRef actualMask = CGImageMaskCreate(
              CGImageGetWidth(maskRef), 
              CGImageGetHeight(maskRef), 
              CGImageGetBitsPerComponent(maskRef), 
              CGImageGetBitsPerPixel(maskRef), 
              CGImageGetBytesPerRow(maskRef), 
              CGImageGetDataProvider(maskRef), NULL, false); 
    CGImageRef masked = CGImageCreateWithMask(imgRef, actualMask); 
    return [UIImage imageWithCGImage:masked]; 
}

和該代碼

// Getting an image imgResult that is center of imgToBeMasked with the surrounding transparent 
NSString *filePath_imgCircleMask = [[NSBundle mainBundle] pathForResource:@"imgCircleMask" ofType:@"png"]; 
NSString *filePath_imgToBeMasked = [[NSBundle mainBundle] pathForResource:@"imgToBeMasked" ofType:@"png"]; 
NSString *filePath_imgCircleHole = [[NSBundle mainBundle] pathForResource:@"imgCircleHole" ofType:@"png"]; 
UIImage *imgCircleMask = [UIImage imageWithContentsOfFile:filePath_imgCircleMask]; 
UIImage *imgToBeMasked = [UIImage imageWithContentsOfFile:filePath_imgToBeMasked]; 
UIImage *imgCircleHole = [UIImage imageWithContentsOfFile:filePath_imgCircleHole]; 
UIImage *imgResult =[funzioni maskImage:imgToBeMasked withMask:imgCircleMask]; 

// Merge imgResult with imgCircleHole so to obtain the img to be masked inside the circle 
CGSize size = CGSizeMake(imgResult.size.width, imgResult.size.height); 
UIGraphicsBeginImageContext(size); 
[imgCircleHole drawInRect:CGRectMake(0,0,size.width, size.height)]; 
[imgResult drawInRect:CGRectMake(0,0,size.width, size.height)]; 
finalImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext();

這裏是圖像。保存並打開它以查看透明度。（imgCircleMask是白色圖像在白色背景上在這裏） imgCircleMask

enter image description here