Re: CIImage resize optimisation
Re: CIImage resize optimisation
- Subject: Re: CIImage resize optimisation
- From: Raphael Sebbe <email@hidden>
- Date: Wed, 15 Apr 2009 08:53:52 +0200
Hi,
well if you look at the entire pipeline, it may well be something like this:
yuv->resize to 640x480->RGB->GL texture upload->lanczos filtering to
320->(either on screen, or bus reading for file writing)
You may have 2 resize ops and a GPU upload (and download?) which are all
expansive.
I can see 2 possible options for making that faster:
- directly ask Quicktime for the expected size
- use a software CIContext for avoiding GPU upload.
Raphael
On Wed, Apr 15, 2009 at 1:41 AM, Dev <email@hidden> wrote:
> Hello,
>
> I use QTKit to grab an image from my webcam. Then i need to resize it into
> a smaller image.
>
> Going from My CIImage, i use two filter "CILanczosScaleTransform" and
> "CICrop"
> to get my image at the correct size. (640x480 to 320x240+crop).
> Doing only that, my CPU go up to 30% of usage while it is at 12%
> without the transformations.
>
> I have a set of C function that works on Bitmaps that is very
> specialized to what i m doing, and would
> allow me to earn a lots of unnecessary transformations (on windows
> that makes my CPU usage to raise to +5% max only) ...
> but here the problem, the rendering of CIImage to a bitmap is worse
> than the filter usage.
>
> here my question, Is there a way of accessing directly the CIImage
> representation so that i can pick my pixels very quickly ?
> the aim is to be very efficient of course ...
>
> thanks to all that will help me.
> --
> Dev
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