ios - 裁剪带有羽化边缘的图像

Posted 2023-02-25

【中文标题】ios - 裁剪带有羽化边缘的图像

【英文标题】：ios - Cropping image with feathered edges

【发布时间】：2014-04-18 17:11:52

【问题描述】：

我想裁剪带有羽化圆的图像。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？

【问题讨论】：

看看这是否可以帮助***.com/questions/17161088/…

嘿，这是什么作物？ SomeGuy 的回答看起来不错！他明白了，否则赏金会发生***！

【参考方案1】：

这个 sn-p 将创建一个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;

【讨论】：

我们有没有可能在不使用阴影和任何颜色渐变的情况下做到这一点？我希望我的图像的边缘（由自定义 uibezierpath 定义）从图像淡入淡出，我不希望它的边界上有阴影或渐变，这可能吗？非常感谢。

【参考方案2】：

这个呢……第一轮图片：

 //round the image

UIImageView *roundView = [[UIImageView alloc] initWithImage:smallImage];
UIGraphicsBeginImageContextWithOptions(roundView.bounds.size, NO, [UIScreen mainScreen].scale);
[[UIBezierPath bezierPathWithRoundedRect:roundView.bounds
                            cornerRadius:roundView.frame.size.width/2] addClip];
[smallImage drawInRect:roundView.bounds];
UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

然后再次将其四舍五入，但使用较小的圆圈并将贝塞尔路径颜色再次设置为白色，但通过调整 alpha 使其半透明...