ios - 使用羽化边缘裁剪图像

Question

我想用羽化圆圈裁剪图像。我用它来裁剪图像，但它只是裁剪成正方形。

 CGImageRef imref = CGImageCreateWithImageInRect([newImage CGImage], faceRect);
 newSubImage = [UIImage imageWithCGImage:imref];

我想要的是用羽毛边缘裁剪？我应该用什么来实现它？

Answer 1

此片段将创建带有羽化边缘的圆形切口

第一个 featherLocations 变量可能是您唯一需要调整的变量

- (UIImage *) featheredImageWithImage:(UIImage *) image
{
    //  Locations of where the feather starts and ends (0 -> 1)
    const CGFloat featherLocations[] = {0.9, 1};

    UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);

    CGContextRef ctx = UIGraphicsGetCurrentContext();

    //  Draw the original image
    [image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];

    //  A 'knock-out' gradient is used to generate a feather effect,
    //  the alpha channel on the colors defines the alpha of the drawn image
    NSArray *gradientColors = @[(id)[UIColor colorWithWhite:0 alpha:1].CGColor,
                                (id)[UIColor colorWithWhite:0 alpha:0].CGColor];

    CGGradientRef gradient = CGGradientCreateWithColors(CGImageGetColorSpace(image.CGImage), (__bridge CFArrayRef)gradientColors, featherLocations);

    //  Because we're changing the draw mode below,
    //  take a snapshot of the current draw settings so we can reset them after
    CGContextSaveGState(ctx);

    //  The kCGBlendModeDestinationIn blend mode will provide a'knock-out' effect on
    //  the previously drawn content, using the alpha channels of the gradient's colors
    CGContextSetBlendMode(ctx, kCGBlendModeDestinationIn);

    const CGPoint gradientCenter = CGPointMake(image.size.width / 2, image.size.height / 2);

    //  The gradient will start at the center (0) and extend to the closest edge (horizontal or vertical)
    const CGFloat startRadius = 0;
    const CGFloat endRadius = MIN(image.size.width,
                                  image.size.height) / 2;

    //  Draw the gradient to eliminate the pixels we don't want
    CGContextDrawRadialGradient(ctx, gradient, gradientCenter, startRadius, gradientCenter, endRadius, (kCGGradientDrawsAfterEndLocation));

    CGGradientRelease(gradient);
    gradient = NULL;

    //  Finally, restore state
    //  (note that in this example CGContextSaveGState and CGContextRestoreGState
    //  are optional because no further drawing happens after this point)
    CGContextRestoreGState(ctx);

    //  Get the UIImage version
    UIImage *featheredImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return featheredImage;
}