Re: Best way to composite/tile multiple CGImages to one image
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 06:02:23 +0000
- Thread-topic: Best way to composite/tile multiple CGImages to one image
>
> On 8 Mar 2014, at 4:12 pm, Trygve Inda <email@hidden> wrote:
>
>> I get the same times doing it this way, but maybe my color spaces are
>> different. The CGImage returned from my AVAsset is:
>>
>> <CGColorSpace 0x100550490> (kCGColorSpaceICCBased; kCGColorSpaceModelRGB;
>> Composite NTSC)
>>
>> I am not really sure what color space to pass into:
>>
>> [NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL.....
>
>>
>> Currently I am using NSDeviceRGBColorSpace.
>>
>> Any thoughts?
>>
>> T.
>
> My guess is that this is a mismatch, because while both spaces are RGB, one is
> NTSC derived and the other probably a simple linear RGB.
>
>
> Unfortunately NSBitmapImageRep only accepts a colour space *name*. It might be
> that the colorspace used by your images doesn't have a name - try using
> CGColorSpaceCopyName on the CGColorSpaceRef you get from CGImageGetColorSpace.
>
> If it's NULL, you'll have to drop down to:
>
> CGBitmapContextCreate(...) which accepts the actual CGColorSpaceRef. This will
> also accept the CGBitmapInfo obtained from your image to ensure that the
> format matches.
>
> Once done compositing, use CGBitmapContextCreateImage to get the CGImage
> (which shouldn't do an additional copy of the buffer as long as you treat the
> image as read-only), then initialize an NSImage from it (again, should be only
> a wrap operation). At this point you'll have an image using the original NTSC
> colorspace. If that has to be drawn to the screen, likely it will need to do a
> similar conversion. Could be that what you gain on the roundabouts you'll lose
> on the swings.
This is slower by about 15%. :(
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