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Re: Best way to composite/tile multiple CGImages to one image
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Re: Best way to composite/tile multiple CGImages to one image


  • Subject: Re: Best way to composite/tile multiple CGImages to one image
  • From: Trygve Inda <email@hidden>
  • Date: Sat, 08 Mar 2014 06:55:40 +0000
  • Thread-topic: Best way to composite/tile multiple CGImages to one image

>
> On 8 Mar 2014, at 5:02 pm, Trygve Inda <email@hidden> wrote:
>
>> This is slower by about 15%.   :(
>
>
> Bummer.
>
> I'm thinking that two seconds to composite 20 x 1920 x 1080 X 32 bits isn't
> too bad actually. That's 165 MB of actual pixel data to iterate over, and at
> each pixel it's going to have to perform considerable cubic downsampling and
> antialiasing operations for the 10x size reduction (have you tried adjusting
> options for image interpolation quality and antialiasing?).
>
> Is there a way to composite this big image on a background thread or perhaps
> composite each contributing image using a different thread so it can at least
> spread the load across the available cores? I must admit that can be tricky
> because each thread will need its own context, but all sharing the same
> underlying destination bitmap buffer (but drawing into a different portion of
> it). Or, if the final image is just destined only for the screen, you could
> make each source image the content of a CALayer and composite it using Core
> Animation, which is then all done in hardware.
>
> --Graham
>
>
>

Interestingly if I call:

CGContextSetInterpolationQuality ([context graphicsPort],
kCGInterpolationNone);

It results in 10% slower processing. The antialiasing setting does not
affect speed at all.

Doing multiple threads will require quite a bit of work - I may give that a
try too. The destination is both screen and a file so I don't think Core
Animation will work.

I might be near the limits of what I can do speed-wise here.  :(



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  • Follow-Ups:
    • Re: Best way to composite/tile multiple CGImages to one image
      • From: Kevin Meaney <email@hidden>
References: 
 >Re: Best way to composite/tile multiple CGImages to one image (From: Graham Cox <email@hidden>)

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