Question

I am trying to save a JPEG image onto the disk using imwrite, seems that I am missing something. I am always getting a black image of around 4KBs. What am I doing wrong here?
Image I see seems fine but once onto the disk, its completely black.

std::vector<int> qualityType(1);
qualityType.push_back(CV_IMWRITE_JPEG_QUALITY);
cv::imwrite("Final.jpg",image,qualityType);

Answer 1

The following code works for me on 8bit (1 and 3 channel) images:

std::vector<int> qualityType;
qualityType.push_back(CV_IMWRITE_JPEG_QUALITY);
qualityType.push_back(90);
cv::imwrite("Final.jpg",image,qualityType);

In your code qualityType is initialized incorrectly. Your vector contains 2 values

{<some unknown number>, CV_IMWRITE_JPEG_QUALITY}

but should be

{CV_IMWRITE_JPEG_QUALITY, <desired quality value>}