Frank, So if I have the ECW image compressed at a 2:1 ratio mapserver will process it faster than if I have the ECW image at 20:1 because mapserver has to decompress the image first. Also the resulting image should be better since I have not compressed it as much.
If I choose to have FORMATOPTION "TARGET=0" which means no compression then my image quality will be better, but it will be slower to download since it is not compressed? John On 11/30/06, Frank Warmerdam <[EMAIL PROTECTED]> wrote:
John Mitchell wrote: > Frank, > > The ECW is already in a compressed format, so this means that the image > is compressed another 95%? This additional compression is for > performance purposes?; does it affect the image quality? John, The imagery is decompressed within mapserver for rendering purposes, and then (if output is to ecw) re-compressed. So the 95% is relative to uncompressed form, not cumulative. Even if the original image was at 95% compression the process of decompressing and recompressing can result in additional image damage. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | President OSGeo, http://osgeo.org
-- John J. Mitchell
