PNG stuff

[Blammo]

I thought about it some more.
Frank,

It would be interesting for example to embed text values for pixel
colors for example.  A mouse over effect could use the data to make some
nice tooltip functions.

The first posting I was after a way to store the creation parameters for
an image, inside of the image for retrieval.  I'm (we're) using quite a
bit of DHTML. and doing an ItemQuery (with no IMGEXT) makes it difficult
to make a subsequent call based on IMGEXT for an overlay object
(transparent PNG).  If the settings like IMGEXT that were used to create
the image were available inside of the image for retrieval, that would
be perfect.

I may yet take you up on it even if it becomes a private PNG chunk for
our use only.  I was just thinking that if some basic parameter related
to the image creation could be embedded into it. That would go a ways
towards solving the problem.

I'l still looking through things to try and figure it out though.

I wonder if it wouldn't be wise to consider something like this as a
post process to GDAL creation.  I suupose the parameters would still
need to be passed from Mapserver though, so I suppose breaking it out
would have little effect.
Thanks for the info.

bobb


Frank Warmerdam wrote:

>On Thu, 9 Dec 2004 23:32:47 -0600, Blammo <bob.basques at ci.stpaul.mn.us> wrote:
>
>
>>All,
>>
>>ok, this is going to sound like a wierd request, but here goes.
>>
>>Is there or has it been thought about, the addition of adding in "Text
>>Strings" to the PNG output, things like IMGEXT, LAYERS, etc.  Something
>>that could be retrievable programetrically (PERL) ?
>>
>>bobb
>>
>>
>
>Bob,
>
>Generally speaking this would be hard to do using the GD PNG output
>since it does not give much low level access to libpng for writing specialized
>chunks (as far as I know).   Potentially I could extend the GDAL PNG output
>to allow adding chunks from "creation options" if that was desired, but it
>would be a bit clumsy.
>
>Best regards,
>
>
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