iphone – 如何在用户触摸图像时擦除部分图像

2019年8月1日 198次阅读

我的大图片目标是在图像上有一个灰色区域,然后当用户在该灰色区域上摩擦时,它会显示下面的图像.基本上像彩票刮刮卡.我已经完成了大量搜索文档以及此站点,但无法找到解决方案.

以下仅是根据用户触摸的位置测试“擦除”图像的概念验证,但它不起作用. 🙁

我有一个检测触摸的UIView,然后通过执行以下操作将移动的坐标发送到UIViewController,该UIViewController在UIImageView中剪切图像：

- (void) moveDetectedFrom:(CGPoint) from to:(CGPoint) to
{
    UIImage* image = bkgdImageView.image;
    CGSize s = image.size;
    UIGraphicsBeginImageContext(s);
    CGContextRef g = UIGraphicsGetCurrentContext();

    CGContextMoveToPoint(g, from.x, from.y);
    CGContextAddLineToPoint(g, to.x, to.y);
    CGContextClosePath(g);
    CGContextAddRect(g, CGRectMake(0, 0, s.width, s.height));
    CGContextEOClip(g);
    [image drawAtPoint:CGPointZero];
    bkgdImageView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [bkgdImageView setNeedsDisplay];
}

问题是触摸被发送到这个方法很好,但原始没有任何反应.

我不正确地做剪辑路径吗？要么？

不太确定…所以任何帮助你都会非常感激.

提前致谢,
乔尔

最佳答案 很多时候我一直试图做同样的事情,只使用Core Graphics,它可以完成,但相信我,效果并不像用户期望的那样平滑和柔和.所以,我知道如何使用OpenCV(开放式计算机视觉库),并且因为它是用C语言编写的,我知道我可以在iPhone上使用它.

使用OpenCV做你想做的事非常容易.

首先,您需要一些函数将UIImage转换为IplImage,它是OpenCV中用于表示各种图像的类型,另一种方式.

+ (IplImage *)CreateIplImageFromUIImage:(UIImage *)image {
CGImageRef imageRef = image.CGImage;
//This is the function you use to convert a UIImage -> IplImage
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

IplImage *iplimage = cvCreateImage(cvSize(image.size.width, image.size.height), IPL_DEPTH_8U, 4);
CGContextRef contextRef = CGBitmapContextCreate(iplimage->imageData, iplimage->width, iplimage->height,
                                                iplimage->depth, iplimage->widthStep,
                                                colorSpace, kCGImageAlphaPremultipliedLast|kCGBitmapByteOrderDefault);
CGContextDrawImage(contextRef, CGRectMake(0, 0, image.size.width, image.size.height), imageRef);


CGContextRelease(contextRef);

CGColorSpaceRelease(colorSpace);

return iplimage;}



+ (UIImage *)UIImageFromIplImage:(IplImage *)image {

//Convert a IplImage -> UIImage
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
NSData * data = [[NSData alloc] initWithBytes:image->imageData length:image->imageSize];
//NSData *data = [NSData dataWithBytes:image->imageData length:image->imageSize];
CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)data);
CGImageRef imageRef = CGImageCreate(image->width, image->height,
                                    image->depth, image->depth * image->nChannels, image->widthStep,
                                    colorSpace, kCGImageAlphaPremultipliedLast|kCGBitmapByteOrderDefault,
                                    provider, NULL, false, kCGRenderingIntentDefault);
UIImage *ret = [[UIImage alloc] initWithCGImage:imageRef];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
[data release];
return ret;}

现在您已经拥有了所需的基本功能,您可以使用IplImage执行任何操作：
  这就是你想要的：

+(UIImage *)erasePointinUIImage:(IplImage *)image :(CGPoint)point :(int)r{
//r is the radious of the erasing
    int a = point.x;
 int b = point.y;
 int position;
 int minX,minY,maxX,maxY;
 minX = (a-r>0)?a-r:0;
 minY = (b-r>0)?b-r:0;
 maxX = ((a+r) < (image->width))? a+r : (image->width);
 maxY = ((b+r) < (image->height))? b+r : (image->height);

 for (int i = minX; i < maxX ; i++)
 {
    for(int j=minY; j<maxY;j++)
    {
        position =  ((j-b)*(j-b))+((i-a)*(i-a));
        if (position <= r*r)
        {
            uchar* ptr =(uchar*)(image->imageData) + (j*image->widthStep + i*image->nChannels);
            ptr[1] = ptr[2] = ptr[3] = ptr[4] = 0;
        }
    }
}
UIImage * res = [self UIImageFromIplImage:image]; 
return res;}

抱歉格式化.

如果您想知道如何将OpenCV移植到iPhone Yoshimasa Niwa’s

如果您想在AppStore上查看当前使用OpenCV的应用程序,请访问：Flags&Faces

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