[magick-users] disk caching

[James Whitwell]

arcanaimperii at imagemagick.org wrote:
>> We've noticed that with large images that ImageMagick transparently
>> caches them on disk.  Is there any way to disable this behaviour?
>>     
>
> You can increase your memory limit like so:
>
>   convert -limit memory unlimited ...
>   
Great!  Can anyone tell me, is this the equivalent C call?

SetMagickResourceLimit (MemoryResource, 4294967295);

I got this via tracing via the debugger.

> However, ImageMagick may still write to the pixel cache on disk if your system
> refuses to honor a memory request.  You can limit the size of the pixel cache
> on disk with the disk limit option:
>
>    convert -limit memory unlimited -limit disk 0 ...
>
> Here ImageMagick throws an exception if the image pixels are cached to disk.
>   
So I'd call SetMagickResourceLimit (DiskResource, 0) for this I guess.  
Does anyone know which exception would be thrown for this, in case I 
want to handle it separately from my normal error handling?  If I then 
called SetMagickResourceLimit (DiskResource, ...) with a non-zero number 
and tried again, that'd let me try again, wouldn't it?

> Last option is to use the Q8 version of ImageMagick rather than Q16.  Q8
> uses less memory than Q16
Yep, we're already on Q8.

Thanks,
 James.