iOS 画出不规则图形

以下为大家提供一种绘制不规则图形的方法，实现原理利用图像的遮盖。

 

//// 这种是路径遮盖法

+ (UIImage*)maskImage:(UIImage*)originImage toPath:(UIBezierPath*)path

{

    UIGraphicsBeginImageContextWithOptions(originImage.size, NO, 0);

    [path addClip];

    [originImage drawAtPoint:CGPointZero];

    UIImage* img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return img;

}

 

 

 

 

////为图像创建透明区域

+ (CGImageRef)CopyImageAndAddAlphaChannel:(CGImageRef)sourceImage

{

    CGImageRef retVal = NULL;

    

    size_t width = CGImageGetWidth(sourceImage);

    size_t height = CGImageGetHeight(sourceImage);

    

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    

    CGContextRef offscreenContext = CGBitmapContextCreate(NULL, width, height,

                                                          8, 0, colorSpace,

                                                          kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little);

    

    if (offscreenContext != NULL)

    {

        CGContextDrawImage(offscreenContext, CGRectMake(0, 0, width, height), sourceImage);

        retVal = CGBitmapContextCreateImage(offscreenContext);

        CGContextRelease(offscreenContext);

    }

    

    CGColorSpaceRelease(colorSpace);

    

    return retVal;

}

 

/////利用图像遮盖

+ (UIImage*)maskImage:(UIImage *)image withMask:(UIImage *)maskImage

{

CGImageRef maskRef = maskImage.CGImage;

CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),

                                        CGImageGetHeight(maskRef),

                                        CGImageGetBitsPerComponent(maskRef),

                                        CGImageGetBitsPerPixel(maskRef),

                                        CGImageGetBytesPerRow(maskRef),

                                        CGImageGetDataProvider(maskRef), NULL, true);

 

CGImageRef sourceImage = [image CGImage];

CGImageRef imageWithAlpha = sourceImage;

    

//add alpha channel for images that don't have one (ie GIF, JPEG, etc...)

//this however has a computational cost

if (CGImageGetAlphaInfo(sourceImage) == kCGImageAlphaNone) {

imageWithAlpha = [ImageUtil CopyImageAndAddAlphaChannel:sourceImage];

}

 

CGImageRef masked = CGImageCreateWithMask(imageWithAlpha, mask);

CGImageRelease(mask);

 

//release imageWithAlpha if it was created by CopyImageAndAddAlphaChannel

    if (sourceImage != imageWithAlpha) {

        CGImageRelease(imageWithAlpha);

    }

 

UIImage* retImage = [UIImage imageWithCGImage:masked];

CGImageRelease(masked);

 

return retImage;

 

}

评论

1 楼 softlanh 2014-05-19  

如果我用第一种方法截取一个不规则图形，截取后只保留需要的截取后的图怎么处理