Mapserver/GD JPEGs

[Stephen Davies]

Thanks Jeff.
That seems to be the issue.
How did you know that INTERLACE=OFF was relevant to JPEGs? As I read the 
doco, it is only relevant for PNG and GIF images.

Do you now if phones have the same aversion to interlaced GIFs?

Cheers and thanks,
Stephen Davies

On Tuesday 27 June 2006 22:46, Jeff Hoffmann wrote:
> Stephen Davies wrote:
> > Last week I posted a request regarding comments in JPEGs and their
> > apparent effect on Motorola 3G telephones.
> >
> > Since then I have found that a) the issue seems to affect all WAP
> > phones and b) it is not just comments that cause the problem.
> >
> > It seems that these devices can only handle very simple images and
> > those generated by Mapserver/GD fall outside their capabilities.
> >
> > I have found that, as well as removing the comments from my map
> > images, I have to go further.
> >
> > My current work-around is to use a PERL script to generate the map
> > image to disk and then use the mogrify utility from Image Magik to
> > "clean" it. The mogrify command is simply:
> >
> > mogrify -quality 100 image.jpg
> >
> > but whatever this does to the image is enough to make it
> > displayable on a telephone when sent as an img src=.
> >
> > If anybody knows more about what is happening here and/or what the
> > underlying problem is, I would love to hear it.
>
> I don't really know a lot of details about what you're doing, but I
> do know that in my experience, phones don't like progressive JPEGs so
> I turn that option off (INTERLACE OFF for older versions or
> FORMATOPTION "INTERLACE=OFF" for newer versions that use an
> OUTPUTFORMAT block).  I think it's enabled by default, so if you
> don't have an INTERLACE setting, it's most likely creating
> progressive JPEGs.  (I'd guess mogrify may be re-encoding from
> progressive to non-progressive, and that's why you're seeing the
> behavior you're seeing.)
>
>
> --
> Jeff Hoffmann
> Head Plate Spinner
> PropertyKey.com

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