file loaded from std::ifstream to opencv image

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Hi all,

I have a image file as a byte buffer loaded using a Input stream as below.

std::ifstream is("image.jpg", std::ifstream::binary);
char * buffer; // image.jpg store in this buffer

Now has some difficulties for me to convert this one into a opencv image. Unfortunately I cannot use cvLoadImage function. I tried below but failed.

 cv::Mat mat= cv::Mat(imageHeight, imageWidth, CV_8UC3, buffer);

Getting an error when I want to display it.

cv::imshow("Img", mat);

Please help. Thanks