grabCut中的参数不正确(图像必须具有CV_8UC3类型)

Question

我使用以下代码使用grabCut算法:

cv::Mat img=[self cvMatFromUIImage:image];

cv::Rect rectangle(10,10,300,150);

cv::Mat result; // segmentation (4 possible values)
cv::Mat bgModel,fgModel; // the models (internally used)
// GrabCut segmentation
cv::grabCut(img,    // input image
            result,      // segmentation result
            rectangle,   // rectangle containing foreground
            bgModel,fgModel, // models
            3,           // number of iterations
            cv::GC_INIT_WITH_RECT); // use rectangle
// Get the pixels marked as likely foreground
cv::compare(result,cv::GC_PR_FGD,result,cv::CMP_EQ);
// Generate output image
cv::Mat foreground(img.size(),CV_8UC3,
                   cv::Scalar(255,255,255));
result=result&1;
img.copyTo(foreground, result);
            result);

image=[self UIImageFromCVMat:foreground];
ImgView.image=image;

转换UIImage为的代码Mat image如下所示

- (cv::Mat)cvMatFromUIImage:(UIImage *)imge
{
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(imge.CGImage);
    CGFloat cols = imge.size.width;
    CGFloat rows = imge.size.height;

    cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels

    CGContextRef contextRef = CGBitmapContextCreate(
                                        cvMat.data,     // Pointer to  data
                                        cols,           // Width of bitmap
                                        rows,           // Height of bitmap
                                        8,              // Bits per component
                                        cvMat.step[0],  // Bytes per row
                                        colorSpace,     // Colorspace
                                        kCGImageAlphaNoneSkipLast |
                                        kCGBitmapByteOrderDefault); 
                                               // Bitmap info flags

    CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), imge.CGImage);
    CGContextRelease(contextRef);
    CGColorSpaceRelease(colorSpace);

    return cvMat;
}

但我得到了错误

OpenCV错误:在grabCut中有错误的参数(图像必须具有CV_8UC3类型).

如果我换 cv::Mat cvMat(rows, cols, CV_8UC4);行,cv::Mat cvMat(rows, cols, CV_8UC3); 那我就明白了<Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaNoneSkipLast; 342 bytes/row..

我在这里很困惑.

请帮忙

Answer 1

问题似乎是,你得到的图像有一个alpha通道,而grabcut需要一个没有alpha通道的rgb图像.所以你需要摆脱额外的渠道.

例如,您可以使用此功能执行此操作:

cv::cvtColor(img , img , CV_RGBA2RGB);

这会解决您的问题吗？