Hi Guennadi,
On Saturday 07 August 2010 15:20:58 Guennadi Liakhovetski wrote:
> On Sat, 7 Aug 2010, lawrence rust wrote:
[snip]
> > A mean squared error metric such as hypot() could be better but requires
> > FP. An integer only version wouldn't be too difficult.
>
> No FP in the kernel. And I don't think this simple task justifies any
> numerical acrobatic. But we can just compare x^2 + y^2 - without an sqrt.
> Is it worth it?
What about comparing areas ? The uvcvideo driver does (rw and rh are the
request width and request height, format is a structure containing an array of
supported sizes)
/* Find the closest image size. The distance between image sizes is
* the size in pixels of the non-overlapping regions between the
* requested size and the frame-specified size.
*/
rw = fmt->fmt.pix.width;
rh = fmt->fmt.pix.height;
maxd = (unsigned int)-1;
for (i = 0; i < format->nframes; ++i) {
__u16 w = format->frame[i].wWidth;
__u16 h = format->frame[i].wHeight;
d = min(w, rw) * min(h, rh);
d = w*h + rw*rh - 2*d;
if (d < maxd) {
maxd = d;
frame = &format->frame[i];
}
if (maxd == 0)
break;
}
--
Regards,
Laurent Pinchart
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