[mapserver-users] Optimising Image quality

[Tim Sutton]

Hi

Thank you for your replies. My preference _is_ to use PNG as I prefer
to use 'open' formats.I do all my development on Linux and my testing
with Linux / Mozilla. When testing with PNG support on IE 5.0, I
found that IE prompted to 'save file as' instead of displaying the png
image as expected. Further, under IE 5.0 when using PNG + rosa, no
image was displayed. Is there something I am missing? Which browsers
actually support PNG? Which ones support PNG with transparency. Could
there be some problem with the IE browser config?

Many thanks

Tim

On Wed, 24 Oct 2001, Ed McNierney wrote:

> Tim -
>
> Your thoughts about JPG are correct.  JPG is a better choice for maps
> with photographic basemaps; PNG is better for other maps.  I would like
> to suggest that you reconsider your feelings against PNG.
>
> I just took a quick look at the last 50,000 user visits to TopoZone, and
> 98.7% of them were with browsers that support the kinds of PNG images
> MapServer generates.  No, that's not universal, but you're never going
> to reach 100.00% (0.17% of the visits were with Netscape 2.x browsers!).
> The TopoZone site doesn't use PNG images (they're GIF) so there isn't a
> self-selection going on here - non-PNG browsers can use TopoZone just
> fine.
>
> The TopoZone site opened two years ago, and even then we encountered
> only one serious problem in PNG support.  Our maps were all originally
> PNG tiles, and Microsoft Internet Explorer 4.x has a bug that prevents
> 8-bit palettized PNG images from printing correctly in some
> circumstances.  We switched to GIF to avoid this problem, but it's a
> two-year-old issue.  As of today (the same 50,000 visit sample) 95% of
> all TopoZone visitors using Internet Explorer are running 5.x or 6.x.
>
> Many browsers that "don't support PNG" tend to fail in PNG's support for
> transparency.  That's not relevant to MapServer.
>
> 	- Ed
>
> Ed McNierney
> Chief Mapmaker
> TopoZone.com
> ed at topozone.com
> (978) 251-4242
>
>
>
> -----Original Message-----
> From: Tim Sutton [mailto:sutton_t at giug.net]
> Sent: Wednesday, October 24, 2001 4:23 AM
> To: MapServer Mailing List
> Subject: [mapserver-users] Optimising Image quality
>
>
> Hi
>
> I have the cvs mapserver running. I am trying to improve the quality
> of the map output. If I use jpeg, the images (comprised mainly of
> lines and labels) have quite a lot of 'noise'. I suspect the jpeg
> output would be more suitable for maps containing raster backdrops
> (large colour palettes with few areas of contiguous colour). I can't
> use PNG as it is not universally supported by browsers yet.
>
> Can anyone tell me where to get hold of the GD1.2 so that I can create
> GIF's on the fly? The GD project site no longer lists it (for
> obvious reasons I suppose).
>
> Alternatively, is there any way to improve the quality of jpeg images
> produced? I have tried the IMAGEQUALITY [int] paramter. Although the
> documentation does not explicitly state it, I presume [int] is a
> percentage 0-100 value. I tried the extremes in this range with no
> visible improvement in image output quality.
>
> Any suggestions will be greatly appreciated.
>
> Thanks
>
> Tim
>