Using libjpeg, compressing Webcam Image

void VideoCaptureTexture::write_JPEG_file (char * filename, int quality)
{
	/* This struct contains the JPEG compression parameters and pointers to
	* working space (which is allocated as needed by the JPEG library).
	* It is possible to have several such structures, representing multiple
	* compression/decompression processes, in existence at once.  We refer
	* to any one struct (and its associated working data) as a "JPEG object".
	*/
	struct jpeg_compress_struct cinfo;
	/* This struct represents a JPEG error handler.  It is declared separately
	* because applications often want to supply a specialized error handler
	* (see the second half of this file for an example).  But here we just
	* take the easy way out and use the standard error handler, which will
	* print a message on stderr and call exit() if compression fails.
	* Note that this struct must live as long as the main JPEG parameter
	* struct, to avoid dangling-pointer problems.
	*/
	struct jpeg_error_mgr jerr;
	/* More stuff */
	FILE * outfile;		/* target file */
	JSAMPROW row_pointer[1];	/* pointer to JSAMPLE row[s] */
	int row_stride;		/* physical row width in image buffer */

	/* Step 1: allocate and initialize JPEG compression object */

	/* We have to set up the error handler first, in case the initialization
	* step fails.  (Unlikely, but it could happen if you are out of memory.)
	* This routine fills in the contents of struct jerr, and returns jerr's
	* address which we place into the link field in cinfo.
	*/
	cinfo.err = jpeg_std_error(&jerr);
	/* Now we can initialize the JPEG compression object. */
	jpeg_create_compress(&cinfo);

	/* Step 2: specify data destination (eg, a file) */
	/* Note: steps 2 and 3 can be done in either order. */

	/* Here we use the library-supplied code to send compressed data to a
	* stdio stream.  You can also write your own code to do something else.
	* VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
	* requires it in order to write binary files.
	*/
	if ((outfile = fopen((filename + fileNumber++), "wb")) == NULL) {
		fprintf(stderr, "can't open %s\n", filename);
		// exit(1);
	}
	jpeg_stdio_dest(&cinfo);

	/* Step 3: set parameters for compression */

	/* First we supply a description of the input image.
	* Four fields of the cinfo struct must be filled in:
	*/
	cinfo.client_data = (void*)&outfile;  
	cinfo.image_width = grabImage->Width(); 	/* image width and height, in pixels */
	cinfo.image_height = grabImage->Height();
	cinfo.input_components = 3;		/* # of color components per pixel */
	cinfo.in_color_space = JCS_RGB; 	/* colorspace of input image */
	/* Now use the library's routine to set default compression parameters.
	* (You must set at least cinfo.in_color_space before calling this,
	* since the defaults depend on the source color space.)
	*/
	jpeg_set_defaults(&cinfo);
	/* Now you can set any non-default parameters you wish to.
	* Here we just illustrate the use of quality (quantization table) scaling:
	*/
	jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);

	/* Step 4: Start compressor */

	/* TRUE ensures that we will write a complete interchange-JPEG file.
	* Pass TRUE unless you are very sure of what you're doing.
	*/
	jpeg_start_compress(&cinfo, TRUE);

	/* Step 5: while (scan lines remain to be written) */
	/*           jpeg_write_scanlines(...); */

	/* Here we use the library's state variable cinfo.next_scanline as the
	* loop counter, so that we don't have to keep track ourselves.
	* To keep things simple, we pass one scanline per call; you can pass
	* more if you wish, though.
	*/
	row_stride = grabImage->Width() * 3;	/* JSAMPLEs per row in image_buffer */


	const int BYTE_SIZE = (160 * 3);
	U8 lineBuffer[BYTE_SIZE];
	for (int y = 0; y < grabImage->Height(); y++)
	{
		int j = 0;
		for (int x=0; x < grabImage->Width(); x++)
		{Con::printf("j: %d.\n", (x*3));
			float r,g,b;
			if (CVFAILED(grabImage->GetPixel(x,y,r,g,b)))
			{
				Con::printf("GetPixel Error!\n");
			}
			else
			{
				lineBuffer[x * 3] = r;
				lineBuffer[x * 3 + 1] = g;
				lineBuffer[x * 3 + 2] = b;
			}
			
		}

		row_pointer[0] = & lineBuffer[0];
		(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
	}

	/* Step 6: Finish compression */

	jpeg_finish_compress(&cinfo);
	/* After finish_compress, we can close the output file. */
	fclose(outfile);

	/* Step 7: release JPEG compression object */

	/* This is an important step since it will release a good deal of memory. */
	jpeg_destroy_compress(&cinfo);

	/* And we're done! */

}