how to compress the whole image on one run (libjpeg IJG)?

[vanselm]

Hello,

since I loose the control of my application, as soon as I start the compression/decompression process of the incoming image frame (from the usb camera), I tried to implement the compression in another way than standard. Normally, there is a while loop, where the image is compressed row for row. Maybe this while loop stucks my programm. Therefore I tried to do the compression in one step by the following code:

JSAMPROW row_pointer[1];        /* pointer to a single row */
	int row_stride;                 /* physical row width in buffer */
	row_stride = m_compressInfo.image_width * 3;   /* JSAMPLEs per row in image_buffer */

	unsigned char* copyPointer =(unsigned char*) m_pcImageMemory;

	// how many rows per run should be compressed
	unsigned int howManyRows =  m_compressInfo.image_height / 48;

	// compress the raw data row by row
	while (m_compressInfo.next_scanline < m_compressInfo.image_height)
	{
		// define the next row of raw data
		row_pointer[0]  =  copyPointer;
		//jpeg_write_scanlines(&m_compressInfo, row_pointer, 1);
		//copyPointer += row_stride;
		jpeg_write_scanlines(&m_compressInfo, row_pointer, howManyRows);
		copyPointer += row_stride*howManyRows;
	}

Even, if I reduce the number of rows to be compressed to 10 rows (image_height = 480 px), then there is an exception however. The exception occures in the function "null_convert()" within the file jccolor.c.

Could you tell me please, what is my mistake and how to compress more than 1 row in one step?

Thanks.

best regards,

vanselm

[nahpetsdi]

Is your question still valid?

[vanselm]

Actually, I'm using another library now (libjpeg-turbo). But I'm still curious how could I do it with the jpeglib library. So if you know how to achieve it, you can post your solution here.