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c++imageimage-processingopencvjpeg

opencv read jpeg image from buffer

I have an unsigned char* buffer containing data of a jpeg image. I would like to display that image using c++ and opencv. If i do:

Mat img(Size(640, 480), CV_8UC3, data);
namedWindow("image", 1);
imShow("image", img);

I get a noisy mess of pixels.

I suppose it's because the data is jpeg (with a header). Because this works:

Mat imgbuf(Size(640, 480), CV_8UC3, data);
Mat img = imdecode(imgbuf, CV_LOAD_IMAGE_COLOR);

BUT I cannot use the imdecode function as it is from highgui.h which is based upon GTK 2, and in my project I use GTK 3.

So, how can I display the buffer data? Is there a way to decode the jpeg image other than imdecode in opencv, if that's the problem. I don't really want to have to rebuild opencv with Qt...

Any other suggestions?

(Using Linux)

Solution

  • I have decompressed the JPEG image using libjpeg using the standard procedure described in the libjpeg API documentation under 'Decompression details'.

    After having decompressed the data you can use it to construct the cv::Mat. Mind you, the decompressed image is in RGB format, whereas openCV uses a BGR format so a cvtColor() operation with format CV_RGB2BGR is needed.