A little progress

Well I managed to get the quickcam displaying the full resolution image using opencv. It turns out that it was capturing at 640x480 the whole time, it just wasn't displaying the whole image. A bit of tweaking to the capture properties and everything started working correctly. Specifically I needed to add these lines:

cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, 640);
cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, 480);

I was also having a little bit of trouble getting at the raw image data from C# as you access it like this using C:

pix = ((uchar*)(img->imageData + img->widthStep*y))[x];

I ended up writing a function that looks like this (where imageData is an IntPtr):

/// This method is used to get the value of a single pixel from the
/// underlying C array.
private unsafe byte GetPixel(int x, int y)
{
// the image data is in one long contiguous array so we need to
// skip y rows of widthstep values before adding our x value to
// index to the right x point in the right row.
return (byte)(((byte*)this.Image.imageData) + this.Image.widthStep * y)[x];
}

Hey... it works :-)