How to make OpenCV IplImage for 16 bit gray-data?

Question

This code is for 8 bit data to make gray-scale IplImage.

    IplImage* img_gray_resize = NULL;
    img_gray_resize = cvCreateImage(cvSize(320, 256), IPL_DEPTH_8U, 1);
    DWORD   dwCount;
    LVDS_SetDataMode(0); // o for 8 bit mode and 1 for 16 bit mode
    dwCount = (LONG)320 * (LONG)256;
    unsigned char* m_pImage = NULL;
    m_pImage = new unsigned char[320 * 256]; 
    for (int i=0; i<320 * 256; i++) m_pImage[i] = NULL;
    LVDS_GetFrame(&dwCount, m_pImage);
    int width = 320;
    int height = 256;
    int nn = 0;
    int ii = 0;
    for (int y=0; y<height; y++) 
    {
        for (int x=0; x<width; x++)  
        {
            ii = y * width + x;
            if(nn < (height*width))
                img_gray_resize->imageData[ii] = m_pImage[nn++];
        }
    }
    delete [] m_pImage;

I need to display 16 bit gray-scale image. If I display 8 bit data, some information is missing from the image. However, LVDS_SetDataMode() can provide both types of data. I am using a library for frame grabber device. Please help me.

Answer 1

as I know,only 8bit data can be displayed,you need to find the best way to convert the 16bit to 8bit to minimize the information you lose. Histogram equalization can be applyed to do this.

Answer 2

16 bit images should be stored in IPL_DEPTH_16U (or CV_16U) mode. This is the correct memory layout.

However, displaying them depends on your display hardware.
Most regular display APIs, e.g. OpenCV's highgui, can only display 8-bit images.
To actually display the image, you will have to convert your image to 8-bits for display.

You will need to decide how to do this. There are many ways to do this, depending on your application and complexity. Some options are:

• Show MSB = right-shift the image by 8 pixels.
• Show LSB = saturate anything above 255.
• In fact, right-shift by any value between 0-8 bits, combined with a cv::saturate_cast to avoid value wrap-around.
• HDR->LDR = Apply dynamic range compression algorithms.

Answer 3

Finally, I have solved the problem by following way:

 dwCount = (LONG)320 * (LONG)256 * 2;
 LVDS_SetDataMode(1);
 img_gray_resize->imageData[ii] = m_pImage[nn++] >> 6;

Just shift bits to right (2, 3, 4, 5, 6, ...), where you get good result, use that value.