OpenCV2.3 imwrite saves black image

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>}

Answer 2

imwrite prints on a 0 to 255 scale, but your image is in a 0 to 1 scale. To scale up, use this line:

image.convertTo(image, CV_8UC3, 255.0);

Answer 3

I only had to convert it to 16bit image

image.convertTo(image,CV_16UC3,255,255);

as per document, 8 or 16 bit images can be saved.