ios - 在 iOS 中用另一个实际图像掩盖透明图像

Question

我有两张图像，一张是带有一些边缘/边框的透明蒙版，另一张是实际图像。我想合并它们。



我使用以下代码来屏蔽和组合图像:

 - (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

    // create a bitmap graphics context the size of the image
    CGFloat dim = MIN(image.size.width, image.size.height);
    CGSize size = CGSizeMake(dim, dim);
    UIGraphicsBeginImageContextWithOptions(size, NO, .0);
    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithOvalInRect:(CGRect){ CGPointZero, size }];
    [bezierPath fill];
    [bezierPath addClip];
    CGPoint offset = CGPointMake((dim - image.size.width) * 0.5, (dim - image.size.height) * 0.5);
    [image drawInRect:(CGRect){ offset, image.size }];
    UIImage *ret = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return ret;
}

结果:



在结果图像中，用作掩码的图像的边框缺失 .有人可以帮我吗？

Answer 1

我为 ios 编写了一个 mask 类别(好吧，它基本上是跨平台的，因为 CoreImage 无论如何都在两个平台上:

github project

核心功能归结为这一点(例如)

UIImage *person = ...
UIImage *circle = ...
UIImage *result = [person imageMaskedWith:circle];

UIImageView *redbox = [[UIImageView alloc] initWithImage:result];
redbox.backgroundColor = [UIColor redColor]; //this can be a gradient!

来自类的主要部分代码:

CGImageRef imageReference = image.CGImage;
CGImageRef maskReference = mask.CGImage;
CGRect rect = CGRectMake(0, 0, CGImageGetWidth(imageReference), CGImageGetHeight(imageReference));

// draw with Core Graphics
UIGraphicsBeginImageContext(rect.size);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(bitmap, 0.0, rect.size.height);
CGContextScaleCTM(bitmap, 1.0, -1.0);

CGContextClipToMask(bitmap, rect, maskReference);
CGContextDrawImage(bitmap, rect, imageReference);

newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();