如何屏蔽 UIView

Question

我正在开发一个应用程序，我通过代码绘制 UIView 并用 UIColor 填充它。接下来我要加载 mask.png 文件（没有透明度，只有黑白）并遮盖 UIView 以更改其视觉外观。

知道如何做到这一点吗？

Answer 1

// Create your mask layer
CALayer* maskLayer = [CALayer layer];
maskLayer.frame = CGRectMake(0,0,yourMaskWidth ,yourMaskHeight);
maskLayer.contents = (__bridge id)[[UIImage imageNamed:@"yourMaskImage.png"] CGImage];

// Apply the mask to your uiview layer        
yourUIView.layer.mask = maskLayer;

记得导入 QuartzCore 并添加框架

#import <QuartzCore/QuartzCore.h>

这很简单，但我没有在任何地方找到答案！

Answer 2

iOS 8 引入了 maskView 属性，该属性允许您使用备用视图来提供遮罩图像。在 Swift 中：

if let maskImage = UIImage(named: "MaskImage") {
    myView.maskView = UIImageView(image: maskImage)
}

请注意，您需要提供实际上具有透明度的图像；具有白色部分（不透明）和黑色部分（透明）的图像将不起作用。

Answer 3

您也许可以使用 CGContextClipToMask：

-(void) drawRect:(CGRect)dirty {
  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextSaveGState( context );
  CGContextClipToMask( context , [self bounds] , [self maskImage] );
  [super drawRect:dirty]; // or draw your color manually
  CGContextRestoreGState( context );
}

Answer 4

我使用上面的代码创建了一个类别：

UIView+ImageMask.h ：

#import <UIKit/UIKit.h>

@interface UIView (ImageMask)

- (void) maskWithImage:(UIImage*) mask;
- (void) maskWithImage:(UIImage*)mask size:(CGSize)maskSize;
- (void) removeMask;

@end

UIView+ImageMask.m ：

#import <QuartzCore/QuartzCore.h>

#import "UIView+ImageMask.h"

@implementation UIView (ImageMask)

- (void) maskWithImage:(UIImage*) mask {
    [self maskWithImage:mask size:mask.size];
}

- (void) maskWithImage:(UIImage*)mask size:(CGSize)maskSize {
    CALayer* maskLayer = [CALayer layer];
    maskLayer.frame = CGRectMake(0, 0, maskSize.size.width, maskSize.size.height);
    maskLayer.contents = (__bridge id)[mask CGImage];

    // Apply the mask to your uiview layer
    self.layer.mask = maskLayer;
}

- (void) removeMask {
    self.layer.mask = nil;
}

@end

Answer 5

谢谢drawonward，

最终得到了这个函数：

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

    UIGraphicsBeginImageContext(image.bounds.size);
    [image.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();


    CGImageRef maskRef = maskImage.CGImage; 

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                        CGImageGetHeight(maskRef),
                                        CGImageGetBitsPerComponent(maskRef),
                                        CGImageGetBitsPerPixel(maskRef),
                                        CGImageGetBytesPerRow(maskRef),
                                        CGImageGetDataProvider(maskRef), NULL, false);

    CGImageRef masked = CGImageCreateWithMask([viewImage CGImage], mask);
    return [UIImage imageWithCGImage:masked];

}

Answer 6

Swift 2.0

将 UIImage 和遮罩图像传递给此函数，您将获得遮罩图像作为 UIImage。

func maskImage(image:UIImage, mask:(UIImage))->UIImage{

    let imageReference = image.CGImage
    let maskReference = mask.CGImage

    let imageMask = CGImageMaskCreate(CGImageGetWidth(maskReference),
                                  CGImageGetHeight(maskReference),
                                  CGImageGetBitsPerComponent(maskReference),
                                  CGImageGetBitsPerPixel(maskReference),
                                  CGImageGetBytesPerRow(maskReference),
                                  CGImageGetDataProvider(maskReference), nil, true)

   let maskedReference = CGImageCreateWithMask(imageReference, imageMask)

   let maskedImage = UIImage(CGImage:maskedReference!)

   return maskedImage
}