Iphone UIImage圆角

我尝试在UIImage上获得圆角，到目前为止，我读到的，最简单的方法是使用遮罩图像。为此，我使用了Elements iPhone示例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总是为零，我没有发现错误

- (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;
}

-（UIImage*）图像按比例缩放到大小：（CGSize）targetSize
{
CGSize imageSize=[自身大小]；
浮动宽度=imageSize.width；
浮动高度=imageSize.height；
//scaleFactor将是我们将
//用于调整大小。例如，如果我们缩小
//将图像减半，scaleFactor将为0.5
//scaledWidth和scaledHeight将为原始值，
//乘以scaleFactor。
//
//重要提示：“TargetLight”是空间的大小
//我们正在接近。缩放高度就是
//一旦我们考虑到
//考虑保持比例的理想
float scaleFactor=0.0；
浮动缩放宽度=targetSize.width；
浮动缩放高度=targetSize.height；
CGPoint thumbnailPoint=CGPointMake（0,0）；
//因为不是所有的图像都是正方形的，所以我们需要缩放
//按比例。要做到这一点，我们找到最长的
//边缘，并以此作为指导。
if（CGSizeEqualToSize（imageSize，targetSize）==否）
{ 
//使用longeset边作为参考。如果
//图像比高宽，我们会弄清楚的
//比例因子除以
//预期宽度。否则，我们将使用
//高度。
浮动宽度系数=targetSize.width/宽度；
浮动高度系数=targetSize.height/高度；
if（宽度系数<高度系数）
scaleFactor=宽度因子；
其他的
比例因子=高度因子；
//ex:500*0.5=250（新宽度）
scaledWidth=宽度*缩放因子；
缩放高度=高度*缩放因子；
//将缩略图置于框架的中心。如果
//宽于高，我们需要调整
//垂直绘图点（y轴）
if（宽度系数<高度系数）
thumbnailPoint.y=（targetSize.height-缩放高度）*0.5；
否则如果（宽度因子>高度因子）
thumbnailPoint.x=（targetSize.width-scaledWidth）*0.5；
}
CGContextRef mainViewContentContext；
CGCOLORSPACTEREF色彩空间；
colorSpace=CGColorSpaceCreateDeviceRGB（）；
//根据图像大小创建位图图形上下文
mainViewContentContext=CGBitmapContextCreate（NULL，targetSize.width，targetSize.height，8,0，colorSpace，KCGimageAlphaPremultipledLast）；
//释放rgb颜色空间
CGCOLORSPACTERELEASE（色彩空间）；
if（mainViewContentContext==NULL）
返回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）；
//创建主视图位图内容的CGImageRef，然后
//释放位图上下文
CGImageRef mainViewContentBitmapContext=CGBitmapContextCreateImage（mainViewContentContext）；
CGContextRelease（mainViewContentContext）；
CGImageRef maskImage=[[UIImage IMAGENAME:@“Mask.png”]CGImage]；
CGImageRef resizedImage=CGImageCreateWithMask（mainViewContentBitmapContext，maskImage）；
CGImageRelease（mainViewContentBitmapContext）；
//将已完成大小调整的图像转换为UIImage
UIImage*theImage=[UIImage imageWithCGImage:resizedImage]；
//图像由上面的属性设置保留，因此我们可以
//发布原件
CGImageRelease（resizedImage）；
//返回图像
返回图像；
}

依我看，除非你绝对需要在代码中这样做，只要在上面覆盖一个图像就行了

类似于

- (void)drawRect:(CGRect)rect 
{
    // Drawing code
    [backgroundImage drawInRect:rect];
    [buttonOverlay drawInRect:rect];    
}

---

实际上，除了在那里缩放之外，你什么都没做。您需要做的是通过使用CGPath剪裁图像来“遮罩”图像的角点。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。

问题在于使用了返回全黑图像的CGImageCreateWithMask。我找到的解决方案是使用CGContextClipToMask：

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;

---

它使用剪辑而不是遮罩的原因似乎是颜色空间

苹果的文档如下

面具

---

面具。如果遮罩是图像，则它必须位于DeviceGray颜色空间中，不得具有alpha分量，并且自身不得被图像遮罩或遮罩颜色遮罩。如果遮罩与image参数指定的图像大小不同，则Quartz会缩放遮罩以适合图像。

如果使用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

并与之链接，才能使上述代码正常工作。

这些行如何

// 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();

大家好，试试这个代码

+ (UIImage *)roundedRectImageFromImage:(UIImage *)image withRadious:(CGFloat)radious {

if(radious == 0.0f)
    return image;

if( image != nil) {

    CGFloat imageWidth = image.size.width;
    CGFloat imageHeight = image.size.height;

    CGRect rect = CGRectMake(0.0f, 0.0f, imageWidth, imageHeight);
    UIWindow *window = [[[UIApplication sharedApplication] windows] objectAtIndex:0];
    const CGFloat scale = window.screen.scale;
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, scale);

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextBeginPath(context);
    CGContextSaveGState(context);
    CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM (context, radious, radious);

    CGFloat rectWidth = CGRectGetWidth (rect)/radious;
    CGFloat rectHeight = CGRectGetHeight (rect)/radious;

    CGContextMoveToPoint(context, rectWidth, rectHeight/2.0f);
    CGContextAddArcToPoint(context, rectWidth, rectHeight, rectWidth/2.0f, rectHeight, radious);
    CGContextAddArcToPoint(context, 0.0f, rectHeight, 0.0f, rectHeight/2.0f, radious);
    CGContextAddArcToPoint(context, 0.0f, 0.0f, rectWidth/2.0f, 0.0f, radious);
    CGContextAddArcToPoint(context, rectWidth, 0.0f, rectWidth, rectHeight/2.0f, radious);
    CGContextRestoreGState(context);
    CGContextClosePath(context);
    CGContextClip(context);

    [image drawInRect:CGRectMake(0.0f, 0.0f, imageWidth, imageHeight)];

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

return nil;
}

---

干杯

我根据@epatel的精彩回答，在swift中创建了一个

UIImage

-扩展：

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：

---

要创建圆角图像，我们可以使用quartzcore

首先，如何添加QuartzCore框架

Click  project -Targets
    ->project
       ->BuildPhase
           ->Link Binary with Libraries
             ->Then click + symbol finally select from list and add it

否则

Click  project -Targets
    ->Targets
      ->general
        ->Linked Frameworks and Libraries
          ->Then click + symbol finally select from list and add the QuartzCore framework

现在输入

#import <QuartzCore/QuartzCore.h> 

---

使用图像维度时，创建圆形图像非常容易

cell.messageImage.layer.cornerRadius = image.size.width / 2
cell.messageImage.layer.masksToBounds = true

---

找出最佳且简单的方法如下（没有答案）：

---

非常简单，而且做得很好。

我正在努力绕过故事板中UIImage框的各个角落。我的UIImage有一个名为image的IBOutlet。在阅读了一堆关于这里的帖子后，我简单地添加了3行，效果非常好

import UIKit

然后在viewDidLoad中：

image.layer.cornerRadius = 20.0

image.layer.masksToBounds = true

这适用于Xcode 9中的iOS 11.1。

扩展，具有正确的比例，

UIImageView *imageView;

imageView.layer.cornerRadius = imageView.frame.size.width/2.0f;
imageView.layer.masksToBounds = TRUE;

import UIKit

image.layer.cornerRadius = 20.0

image.layer.masksToBounds = true

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()!
    }

}

let imageView = UIImageView(image: UIImage(named: "myImage"))    
imageView.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
imageView.layer.cornerRadius = 10.0