UIImage圆角

Question

我尝试在UIImage上得到圆角,到目前为止我读到的,最简单的方法是使用蒙版图像.为此我使用了TheElements iPhone Example中的代码和我找到的一些图像大小调整代码.我的问题是resizedImage总是为nil而且我没有找到错误...

- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize
{
    CGSize imageSize = [self size];
    float width = imageSize.width;
    float height = imageSize.height;

    // scaleFactor will be the fraction that we'll
    // use to adjust the size. For example, if we shrink
    // an image by half, scaleFactor will be 0.5. the
    // scaledWidth and scaledHeight will be the original,
    // multiplied by the scaleFactor.
    //
    // IMPORTANT: the "targetHeight" is the size of the space
    // we're drawing into. The "scaledHeight" is the height that
    // the image actually is drawn at, once we take into
    // account the ideal of maintaining proportions

    float scaleFactor = 0.0; 
    float scaledWidth = targetSize.width;
    float scaledHeight = targetSize.height;

    CGPoint thumbnailPoint = CGPointMake(0,0);

    // since not all images are square, we want to scale
    // proportionately. To do this, we find the longest
    // edge and use that as a guide.

    if ( CGSizeEqualToSize(imageSize, targetSize) == NO )
    { 
        // use the longeset edge as a guide. if the
        // image is wider than tall, we'll figure out
        // the scale factor by dividing it by the
        // intended width. Otherwise, we'll use the
        // height.

        float widthFactor = targetSize.width / width;
        float heightFactor = targetSize.height / height;

        if ( widthFactor < heightFactor )
            scaleFactor = widthFactor;
        else
            scaleFactor = heightFactor;

        // ex: 500 * 0.5 = 250 (newWidth)

        scaledWidth = width * scaleFactor;
        scaledHeight = height * scaleFactor;

        // center the thumbnail in the frame. if
        // wider than tall, we need to adjust the
        // vertical drawing point (y axis)

        if ( widthFactor < heightFactor )
            thumbnailPoint.y = (targetSize.height - scaledHeight) * 0.5;

        else if ( widthFactor > heightFactor )
            thumbnailPoint.x = (targetSize.width - scaledWidth) * 0.5;
    }


    CGContextRef mainViewContentContext;
    CGColorSpaceRef colorSpace;

    colorSpace = CGColorSpaceCreateDeviceRGB();

    // create a bitmap graphics context the size of the image
    mainViewContentContext = CGBitmapContextCreate (NULL, targetSize.width, targetSize.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);

    // free the rgb colorspace
    CGColorSpaceRelease(colorSpace);    

    if (mainViewContentContext==NULL)
        return NULL;

    //CGContextSetFillColorWithColor(mainViewContentContext, [[UIColor whiteColor] CGColor]);
    //CGContextFillRect(mainViewContentContext, CGRectMake(0, 0, targetSize.width, targetSize.height));

    CGContextDrawImage(mainViewContentContext, CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledWidth, scaledHeight), self.CGImage);

    // Create CGImageRef of the main view bitmap content, and then
    // release that bitmap context
    CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(mainViewContentContext);
    CGContextRelease(mainViewContentContext);

    CGImageRef maskImage = [[UIImage imageNamed:@"Mask.png"] CGImage];

    CGImageRef resizedImage = CGImageCreateWithMask(mainViewContentBitmapContext, maskImage);
    CGImageRelease(mainViewContentBitmapContext);

    // convert the finished resized image to a UIImage 
    UIImage *theImage = [UIImage imageWithCGImage:resizedImage];

    // image is retained by the property setting above, so we can 
    // release the original
    CGImageRelease(resizedImage);

    // return the image
    return theImage;
}

Answer 1

如果您使用UIImageView显示图像,则只需执行以下操作:

imageView.layer.cornerRadius = 5.0;
imageView.layer.masksToBounds = YES;

并添加边框:

imageView.layer.borderColor = [UIColor lightGrayColor].CGColor;
imageView.layer.borderWidth = 1.0;

我相信您必须导入<QuartzCore/QuartzCore.h>并链接它才能使上述代码生效.

Answer 2

这些线怎么样......

// Get your image somehow
UIImage *image = [UIImage imageNamed:@"image.jpg"];

// Begin a new image that will be the new image with the rounded corners 
// (here with the size of an UIImageView)
UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, 1.0);

// Add a clip before drawing anything, in the shape of an rounded rect
[[UIBezierPath bezierPathWithRoundedRect:imageView.bounds 
                            cornerRadius:10.0] addClip];
// Draw your image
[image drawInRect:imageView.bounds];

// Get the image, here setting the UIImageView image
imageView.image = UIGraphicsGetImageFromCurrentImageContext();

// Lets forget about that we were drawing
UIGraphicsEndImageContext();

Answer 3

我UIImage在swift中创建了一个-extension,基于@ epatel的好答案:

extension UIImage{
    var roundedImage: UIImage {
        let rect = CGRect(origin:CGPoint(x: 0, y: 0), size: self.size)
        UIGraphicsBeginImageContextWithOptions(self.size, false, 1)
        UIBezierPath(
            roundedRect: rect,
            cornerRadius: self.size.height
            ).addClip()
        self.drawInRect(rect)
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

在故事板中测试:

Answer 4

问题是使用CGImageCreateWithMask返回全黑图像.我发现的解决方案是使用CGContextClipToMask代替:

CGContextRef mainViewContentContext;
CGColorSpaceRef colorSpace;

colorSpace = CGColorSpaceCreateDeviceRGB();

// create a bitmap graphics context the size of the image
mainViewContentContext = CGBitmapContextCreate (NULL, targetSize.width, targetSize.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);

// free the rgb colorspace
CGColorSpaceRelease(colorSpace);    

if (mainViewContentContext==NULL)
    return NULL;

CGImageRef maskImage = [[UIImage imageNamed:@"mask.png"] CGImage];
CGContextClipToMask(mainViewContentContext, CGRectMake(0, 0, targetSize.width, targetSize.height), maskImage);
CGContextDrawImage(mainViewContentContext, CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledWidth, scaledHeight), self.CGImage);


// Create CGImageRef of the main view bitmap content, and then
// release that bitmap context
CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(mainViewContentContext);
CGContextRelease(mainViewContentContext);

// convert the finished resized image to a UIImage 
UIImage *theImage = [UIImage imageWithCGImage:mainViewContentBitmapContext];
// image is retained by the property setting above, so we can 
// release the original
CGImageRelease(mainViewContentBitmapContext);

// return the image
return theImage;

Answer 5

在Swift 4中以正确的比例扩展Besi的出色答案：

extension UIImage {

    public func rounded(radius: CGFloat) -> UIImage {
        let rect = CGRect(origin: .zero, size: size)
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        UIBezierPath(roundedRect: rect, cornerRadius: radius).addClip()
        draw(in: rect)
        return UIGraphicsGetImageFromCurrentImageContext()!
    }

}

Answer 6

你实际上并没有做任何其他事情.你需要做的是通过用CGPath剪切它来"掩盖"图像的角落.例如 -

 - (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextBeginTransparencyLayerWithRect(context, self.frame, NULL);
    CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);  
    CGFloat roundRadius = (radius) ? radius : 12.0;
    CGFloat minx = CGRectGetMinX(self.frame), midx = CGRectGetMidX(self.frame), maxx = CGRectGetMaxX(self.frame);
    CGFloat miny = CGRectGetMinY(self.frame), midy = CGRectGetMidY(self.frame), maxy = CGRectGetMaxY(self.frame);

    // draw the arcs, handle paths
    CGContextMoveToPoint(context, minx, midy);
    CGContextAddArcToPoint(context, minx, miny, midx, miny, roundRadius);
    CGContextAddArcToPoint(context, maxx, miny, maxx, midy, roundRadius);
    CGContextAddArcToPoint(context, maxx, maxy, midx, maxy, roundRadius);
    CGContextAddArcToPoint(context, minx, maxy, minx, midy, roundRadius);
    CGContextClosePath(context);
    CGContextDrawPath(context, kCGPathFill);
    CGContextEndTransparencyLayer(context);
}

我建议查看Quartz 2D编程指南或其他一些示例.