[Radiance-general] ra_gif: out of memory error

[Greg Ward]

The -n option of ra_gif is just to save time on large images by subsampling the input pixels.  For small images, setting -n 1 should produce the best results, so there's no reason to set the option higher.  If you don't have enough samples, the neural network color quantizer doesn't have enough information and I guess it loses its mind...

-Greg

> From: Marija Velickovic <maricanis at gmail.com>
> Date: May 16, 2012 6:38:01 AM PDT
> 
> Hi,
> 
> I'm trying to convert radiance image to gif and getting strange error.
> command: ra_gif -n 20 input.hdr output.gif
> error: ra_gif: out of memory
> output image: invalid image with size 0
> 
> If I try the same command without -n option no error 
> command: ra_gif  input.hdr output.gif
> output image: expected output image
> 
> Other info that may be of use in error source determination
> Original Radiance image resolution is quite unusual  -Y 500 +X 7
> I've tried to change values of -n option, and for this image options n<=5 don't produce error and options n>5 give the same error
> ra_gif works without problems with any -n option, if I use other image with more 'normal' aspect ratio
> I've tried few ra_gif executables, in Windows and Linux and all give the same result.
> For -n option in manual there is a description:
> "The −n option specifies a sampling factor for neural network color quantization. This value should be between 1 and 80, where 1 takes the longest and produces the best results in small areas of the image."
> So I've chosen 20, as some optimal value to get good gif images and not too long time.
> I thought that lower -n values would require more memory, but in this case they give correct results, and higher values give memory error.
> 
> Not sure what can be the source of the problem.
> 
> Any ideas?
> Marija
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