[geotk] Efficient subsetting/subsampling of large image

[Martin Desruisseaux]

Jon Blower a écrit :
> Thanks very much!  I had never used ImageReadParam before.  Apologies
> that this wasn't really a geotoolkit question...

No problem :) I'm glad if I can be of any help.


> Out of interest, do you know how much difference it makes if the image
> is compressed (e.g. JPEGs versus BMPs)?  I would imagine that the
> decompression step could have a significant effect on performance.

For subsampling, I'm not sure. For sub-regions, in our tests it really make a 
difference (uncompressed format is faster). However this is very sensitive to 
the actual format used. JPEG is very fast. PNG is slower, maybe twice slower 
than an uncompressed image.

I think that there is not much alternative to empirical tests for this question...

	Martin