OpenCV。圖像作爲灰度而不是RGB返回

Question

我正在iOS上使用OpenCV進行一些實驗。我試圖把一個PNG圖像上的檢測face.Thats的頂部我嘗試在一個deteted面放置圖像：

但我得到這個：

我用這個功能來轉換一個UIImage到：與CvMat

- (cv::Mat)cvMatFromUIImage:(UIImage *)image 
{ 
CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage); 
CGFloat cols = image.size.width; 
CGFloat rows = image.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), image.CGImage); 
CGContextRelease(contextRef); 
CGColorSpaceRelease(colorSpace); 

return cvMat; 
} 

在這裏，我添加圖像：

- (void)processImage:(cv::Mat&)image; 
{ 
cv::vector<cv::Rect> faces; 
cv::Mat frame_gray; 

cvtColor(image, frame_gray, CV_BGRA2GRAY); 
equalizeHist(frame_gray, frame_gray); 

face_cascade.detectMultiScale(frame_gray, faces, 1.1, 2, 0 | CV_HAAR_SCALE_IMAGE, cv::Size(100, 100)); 

for(unsigned int i = 0; i < faces.size(); ++i) 
{ 
    rectangle(image, cv::Point(faces[i].x, faces[i].y), 
       cv::Point(faces[i].x + faces[i].width, faces[i].y + faces[i].height), 
       cv::Scalar(0,255,255)); 
    CGPoint pos; 
    pos.x = faces[i].x; 
    pos.y = faces[i].y; 

    cv::Rect roi(cv::Point(pos.x , pos.y), cv::Size(faces[i].width , faces[i].height )); 
    cv::Mat destinationROI = image(roi); 
    cv::Mat smallImage = [self faceIntoImageView:pos size:CGSizeMake(faces[i].width, faces[i].height)]; 
    smallImage.copyTo(image(roi)); 

} 
} 

-(cv::Mat)faceIntoImageView:(CGPoint)position size:(CGSize)size 
{ 

UIImage* face = [UIImage imageNamed:@"Face1.png"]; 
face = [self imageWithImage:face scaledToSize:size]; 
return [self cvMatFromUIImage:face]; 
} 

Answer 1

你應該換B和R通道。

- (cv::Mat)cvMatFromUIImage:(UIImage *)image 
    { 
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage); 
    CGFloat cols = image.size.width; 
    CGFloat rows = image.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), image.CGImage); 
    CGContextRelease(contextRef); 
    CGColorSpaceRelease(colorSpace); 

//-------swap channels 
std::vector<Mat> ch; 
cv::split(cvMat,ch); 
std::swap(ch[0],ch[2]); 
cv::merge(ch,cvMat); 
//------- 
    return cvMat; 
    }