使用openNi / NITE从Kinect生成jpeg图像

Question

I am trying to generate pass the image frames to a face-detection/tracking algorithm from the Kinect. I've seen that the best way to generate jpeg images from openGL textures is via libjpeg but I'm clueless on how to start. This is what I have on my code now:

//draw image frame to texture       
    const XnRGB24Pixel* pImageRow = g_imageMD.RGB24Data();
    XnRGB24Pixel* pTexRow = g_pTexMap + g_imageMD.YOffset() * g_nTexMapX;

    for (XnUInt y = 0; y < g_imageMD.YRes(); ++y)
    {
        const XnRGB24Pixel* pImage = pImageRow;
        XnRGB24Pixel* pTex = pTexRow + g_imageMD.XOffset();

        for (XnUInt x = 0; x < g_imageMD.XRes(); ++x, ++pImage, ++pTex)
        {
            *pTex = *pImage;
        }

        pImageRow += g_imageMD.XRes();
        pTexRow += g_nTexMapX;
    }

    // Create the OpenGL texture map
    glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP_SGIS, GL_TRUE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, g_nTexMapX, g_nTexMapY, 0, GL_RGB, GL_UNSIGNED_BYTE, g_pTexMap);

So how can I pass on this g_pTexMap thing to be saved as a jpeg image?

Answer 1

OpenGL does not deal with image files. If you want to store an image to a file, passing it to OpenGL is not doing the right thing to do. Instead of passing the data to glTexImage2D you should pass it to libjpeg or another image file access library.

Have a look at imlib2 http://docs.enlightenment.org/api/imlib2/html/

Answer 2

I did try the imlib2 but it seemed difficult to convert openNi XnRGB24Pixel type to the data stream imlib2 is looking for. Imlib2 seems to work more easily with files (eg imageName.jpg) rather than data streams in the memory. I then moved to try out openCV and here is the code I got and edited from an openni-discussion page [link here].

void generateJpeg(const xn::ImageMetaData& g_imageMD){

    //opencv to convert image to jpeg
    printf("Converting image to jpeg.\n");
    cv::Mat colorArr[3]; 
    cv::Mat colorImage; 
    const XnRGB24Pixel* pPixel; 
    const XnRGB24Pixel* pImageRow; 
    pImageRow = g_imageMD.RGB24Data();


    colorArr[0] = cv::Mat(g_imageMD.YRes(),g_imageMD.XRes(),CV_8U); 
    colorArr[1] = cv::Mat(g_imageMD.YRes(),g_imageMD.XRes(),CV_8U); 
    colorArr[2] = cv::Mat(g_imageMD.YRes(),g_imageMD.XRes(),CV_8U); 

    for (int y=0; y<g_imageMD.YRes(); y++){ 
        pPixel = pImageRow; 
        uchar* Bptr = colorArr[0].ptr<uchar>(y); 
        uchar* Gptr = colorArr[1].ptr<uchar>(y); 
        uchar* Rptr = colorArr[2].ptr<uchar>(y); 

        for(int x=0;x<g_imageMD.XRes();++x , ++pPixel){ 
                Bptr[x] = pPixel->nBlue; 
                Gptr[x] = pPixel->nGreen; 
                Rptr[x] = pPixel->nRed; 
        } 

        pImageRow += g_imageMD.XRes(); 
    } 

    cv::merge(colorArr,3,colorImage); 
     IplImage bgrIpl = colorImage;    
    cvSaveImage("image.jpg",&bgrIpl);

}