Re: Getting immutable UIImage data pointer without copy?
Re: Getting immutable UIImage data pointer without copy?
- Subject: Re: Getting immutable UIImage data pointer without copy?
- From: Vince DeMarco <email@hidden>
- Date: Wed, 15 Nov 2017 12:50:04 -0800
The best way would be to use vImage and make a vImage_Buffer from a CGImageRef.
look at the documentation for vImageBuffer_InitWithCGImage()
vImage might end up doing the image conversion you need to do as a bonus.
the vImage API is kind of different, but once you figure out how to use it, you
will notice how powerful it really is.
Vince
> On Nov 14, 2017, at 8:37 PM, Rick Mann <email@hidden> wrote:
>
>
>
>> On Nov 14, 2017, at 20:18 , Jens Alfke <email@hidden> wrote:
>>
>>
>>
>>> On Nov 14, 2017, at 8:11 PM, Rick Mann <email@hidden> wrote:
>>>
>>> Maybe, at least for the bonus question. The bigger question is around the
>>> copy.
>>
>> Where pixmaps live is a pretty complex issue — ideally they live in the
>> GPU’s address space as textures so they can be blitted efficiently, and
>> that’s often (depending on your hardware) not accessible to the CPU at all.
>> But there’s a lot of logic in CoreGraphics and the underlying graphics
>> engines to shuffle the pixmaps back and forth so software can read and write
>> them.
>>
>> Another factor is that the pixmap may be rescaled or translated into
>> different color spaces to optimize rendering it. So there may not exist a
>> default rendering of it at the time you request one, meaning CG will
>> generate a new pixmap for you. (Also, I dunno about UIImage, but NSImage
>> supports image formats like PDF that don’t have a native pixmap
>> representation at all.)
>>
>> I’m not super into graphics, but my gut feeling is that, if you care about
>> optimization details like whether pixmaps are being copied, you should
>> really be using a lower-level graphics API than UIImage, which is mostly a
>> cheap-and-cheerful convenience layer for apps that just need to splat a few
>> PNGs into their GUI.
>
> Well, then let me rephrase it as "unnecessary copies." In this case, I
> (currently) need to manipulate the pixels to generate a new image. I will be
> moving this to a Metal 2 filter soon enough, but for pre-iOS 11 users, I'd
> still like to use as little memory as possible (we use a lot of memory in our
> app).
>
>
> --
> Rick Mann
> email@hidden <mailto:email@hidden>
>
>
> _______________________________________________
>
> Cocoa-dev mailing list (email@hidden)
>
> Please do not post admin requests or moderator comments to the list.
> Contact the moderators at cocoa-dev-admins(at)lists.apple.com
>
> Help/Unsubscribe/Update your Subscription:
>
> This email sent to email@hidden
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden