Re: CoreImage problems with very large images
Re: CoreImage problems with very large images
- Subject: Re: CoreImage problems with very large images
- From: Chris Blackburn <email@hidden>
- Date: Fri, 16 Nov 2007 14:17:43 +0000
Hey,
The image you are trying to process dexpmpresses to an image that is
about 968 megabytes in size. This is almost certainly bigger than your
graphics card VRAM. Assuming that core image is programmer cleverly it
will take the image and break it down into tiles that overlap slightly
and reconstruct the image afterwards. This won't be really slow but it
may well chew up a gig of ram in the process.
If core image is not implemented to deal with large images it might
just give up on the GPU, load the whole lot into RAM and process using
Altivec or SSE. This may well be very very slow indeed.
You might want to try tiling and reconstructing the image yourself so
you never overstep your VRAM.
Chris
On 16 Nov 2007, at 08:07, Jim Crate <email@hidden> wrote:
I'm using CoreImage in an app, but it is unusable with very large
images, e.g. a 52-megabyte 18,000 x 14,000 jpg. A 5000 x 4000 jpg
image loads and processes with great performance, but trying to
process the large image leads to very high memory use and much
swapping to disk. I tried to load the large image in the Core
Image Fun House example app, and ended up force-quitting after
waiting 10-15 minutes.
The old implementation using NSImage could load and process (scale,
rotate, watermark, broken grayscale) the large images, and while it
wasn't fast, it was at least usable.
Is CoreImage just not meant to handle images this big? Or are there
ways to gain acceptable performance with these large images with
CoreImage? Will the problem possibly go away on a Mac Pro?
Thanks,
Jim
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