Frank,<br><br>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.
<br><br>If I choose to have <span class="q">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?<br><br>John<br></span>
<br><div><span class="gmail_quote">On 11/30/06, <b class="gmail_sendername">Frank Warmerdam</b> <<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
John Mitchell wrote:<br>> Frank,<br>><br>> The ECW is already in a compressed format, so this means that the image<br>> is compressed another 95%? This additional compression is for<br>> performance purposes?; does it affect the image quality?
<br><br>John,<br><br>The imagery is decompressed within mapserver for rendering purposes, and<br>then (if output is to ecw) re-compressed. So the 95% is relative to<br>uncompressed form, not cumulative. Even if the original image was
<br>at 95% compression the process of decompressing and recompressing can result<br>in additional image damage.<br><br>Best regards,<br>--<br>---------------------------------------+--------------------------------------<br>
I set the clouds in motion - turn up | Frank Warmerdam, <a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a><br>light and sound - activate the windows | <a href="http://pobox.com/~warmerdam">http://pobox.com/~warmerdam
</a><br>and watch the world go round - Rush | President OSGeo, <a href="http://osgeo.org">http://osgeo.org</a><br><br></blockquote></div><br><br clear="all"><br>-- <br>John J. Mitchell