[udig-devel] Re: ImageIO-GDAL integration

[Aleksander Bandelj]

WRT quality, there is a nice study at 
http://cs.joensuu.fi/~villeh/EI5022-79.pdf

Performance-wise, I don't know of any which would even marginally 
include the relevant variables like disk bandwidth, memory and cache 
size, number of clients and cpu performance. All I can offer is that if 
you have fast disks, lots of space and serve dumb raster imagery to 
large number of concurrent clients, mosaicked TIFF probably performs 
noticeably better than ECW. But, in such scenario, you would ultimately 
want to simply serve cached tiled images from cache to client like 
google does. This is orders of magnitude faster than anything that 
requires decompression and/or scaling.

OTOH, rendering ECWs on smart clients can be even more performant than 
above, since you typically have a fast CPU to burn and ECW bandwidth 
requirements are quite modest.

So, ECW and a client which can perform ECW decompression could be best 
option on convenience and performance. As long as you can afford ECW 
license price, of course :)

Guido Lemoine wrote:
> Is there any quantitative data on ECW versus GeoTIFF comparison 
> (speed, quality)?
> GeoTIFF appears more "open" than ECW, which also has some nasty 
> limitations on
> maximum size allowed in the "free" codec. I recall that GDAL was 
> implementing
> JPEG2000 compression in the GeoTIFF standard, but may be wrong on that.
>
> GL
>
> Aleksander Bandelj wrote:
>
>> My experience is that ECW decoding is much more expensive than TIFF 
>> one. So, compactness yes, speed no. Fine for a single client, but not 
>> so good for a server ...
>>
>> Andrea Aime wrote:
>>
>>> Paul Ramsey ha scritto:
>>>
>>>> I would very much like to see an ECW driver or (even better) a 
>>>> JP2000 driver from this project, as such a thing would be widely 
>>>> useful for end users.  My priority order would be: JP2000, LAN, 
>>>> ECW, AUX.  I assume GeoTIFF is already handled by the existing 
>>>> coverage work?  If not, it would go first.
>>>>
>>> Well, I second Daniele's choice since, at least here in Italy, you 
>>> either support
>>> ECW or they'll start laughing at you. Geotiff is so '90s (it has his 
>>> merits, but
>>> everybody seems to have gone nuts for ECW's speed and compactness).
>>>
>>> Cheers
>>> Andrea
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