从 Mat(OpenCV) 转换为 UIImage 后出现黑色背景

Question

我有一个使用 OpenCV 库的一些功能来编辑图像的应用程序。 将 UIImage 转换为 Mat 并将 Mat 转换为 UIImage 后，图像中出现黑色背景，请告诉我如何修复它

我用来将 UIImage 转换为 Mat 的代码

- (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 (color channels + alpha)

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);

return cvMat;

}

我用来将 Mat 转换为 UIImage 的代码

-(UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
{
    NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize()*cvMat.total()];
    CGColorSpaceRef colorSpace;

if (cvMat.elemSize() == 1) {
    colorSpace = CGColorSpaceCreateDeviceGray();
} else {
    colorSpace = CGColorSpaceCreateDeviceRGB();
}

CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);

// Creating CGImage from cv::Mat
CGImageRef imageRef = CGImageCreate(cvMat.cols,                                 //width
                                    cvMat.rows,                                 //height
                                    8,                                          //bits per component
                                    8 * cvMat.elemSize(),                       //bits per pixel
                                    cvMat.step[0],                            //bytesPerRow
                                    colorSpace,                                 //colorspace
                                    kCGImageAlphaNone|kCGBitmapByteOrderDefault,// bitmap info
                                    provider,                                   //CGDataProviderRef
                                    NULL,                                       //decode
                                    false,                                      //should interpolate
                                    kCGRenderingIntentDefault                   //intent
                                    );


// Getting UIImage from CGImage
UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);

return finalImage;

}

我的代码示例

-(UIImage *)stroked:(UIImage *)image color:(int)color strock:(float)strock {
cv::Mat img = [self cvMatFromUIImage:image];

return [self UIImageFromCVMat:img];

}

Answer 1

功能齐全，没有繁殖问题。 由于提示，我将 kCGImageAlphaNoneSkipLast|kCGBitmapByteOrderDefault 调整为 kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast

kCGImageAlphaNone|kCGBitmapByteOrderDefault 到 kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast