OpenCV imwrite gives washed-out result for jpeg images

Question

I am using OpenCV 3.0 and whenever I read an image and write it back the result is a washed-out image.

code:

cv::Mat img = cv::imrea         


        

Answer 1

You can try to increase the compression quality parameter as shown in OpenCV Documentation of cv::imwrite :

cv::Mat img = cv::imread("dir/frogImage.jpg",-1);

std::vector compression_params;
compression_params.push_back(CV_IMWRITE_JPEG_QUALITY);
compression_params.push_back(100);

cv::imwrite("dir/result.jpg",img, compression_params);

Without specifying the compression quality manually, quality of 95% will be applied.

but 1. you don't know what jpeg compression quality your original image had (so maybe you might increase the image size) and 2. it will (afaik) still introduce additional minor artifacts, because after all it is a lossy compression method.

UPDATE your problem seems to be not because of compression artifacts but because of an image with Adobe RGB 1998 color format. OpenCV interprets the color values as they are, but instead it should scale the color values to fit the "real" RGB color space. Browser and some image viewers do apply the color format correctly, while others don't (e.g. irfanView). I used GIMP to verify. Using GIMP you can decide on startup how to interpret the color values by format, either getting your desired or your "washed out" image. OpenCV definitely doesn't care about such things, since it's not a photo editing library, so neither on reading nor on writing, color format will be handled.