Question

I have a jpeg image in buffer jpegBuffer. I’m trying to pass it to cv::imdecode function:

Mat matrixJprg = imdecode(Mat(jpegBuffer), 1);

I get this error:

/home/richard/Desktop/richard/client/src/main.cc:108: error: no matching function for call to ‘cv::Mat::Mat(char*&)’

This is how I fill jpegBuffer:

FILE* pFile;
long lSize;
char * jpegBuffer;
pFile = fopen ("img.jpg", "rb");
if (pFile == NULL)
{
    exit (1);
}

// obtain file size.
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);

// allocate memory to contain the whole file.
jpegBuffer = (char*) malloc (lSize);
if (jpegBuffer == NULL)
{
    exit (2);
}

// copy the file into the buffer.
fread (jpegBuffer, 1, lSize, pFile);

// terminate
fclose (pFile);

Answer 1

Mat has no constructor that takes a char* argument. Try this instead:

std::ifstream file("img.jpg");
std::vector<char> data;

file >> std::noskipws;
std::copy(std::istream_iterator<char>(file), std::istream_iterator<char>(), std::back_inserter(data));

Mat matrixJprg = imdecode(Mat(data), 1);

EDIT:

You should also take a look at LoadImageM.

If you have your data already in a char* buffer one way is to copy the data into an std::vector.

std::vector<char> data(buf, buf + size);