24 bit to 8 bit gd conversion

[Yewondwossen Assefa]

Steve Lime wrote:
> So you're basically talking about a 24-bit GIF or PNG outformat block correct?
> Seems like a reasonable idea to me. 
> 
> As an aside I also wish we could do auto quantization with a format like PNG that 
> supports both 8 and 24-bit pixels. For example, many applications allow you to
> set background imagery and in that case you need true color output. However,
> you typically need to use the 24-bit format when that imagery is off as well resulting
> in uncessarily large files.
> 
> Perhaps we might consider a parameter like:
> 
>   QUANTITIZE TRUE|FALSE|AUTO
> 



  I filed  an enhancement bug on this (1690) for both elements. Like I 
mentionned, we need to do more tests to be sure that things are correct 
or not.  I will update the bug with the results.


Thanks.

> Steve
> 
> 
>>>>Yewondwossen Assefa <assefa at DMSOLUTIONS.CA> 02/26/06 2:02 PM >>>
> 
> Hi There,
> 
>   We were doing few tests last week on the possiblity to do 24 bit 
> rendering using png24 and convert the output to 8 bit at the end. The 
> main reason being that we had issues with the color limitation on some 
> of the maps we were using. And also the fact that antialising was only 
> available in 24bits.
>   We were experimenting with the gd function 
> gdImageCreatePaletteFromTrueColor(img, 0, 256);  to achieve that, 
> calling the fucntion just before the save.
>   It seems to give decent results, although I think we need to do more 
> tests and there seems to be an issue with transparencies.
>   The idea was that if It was a good enough, It could make it into 
> something like an outputformat option.
> 
>   What do you think in general about this issue ?
> 
>   Thanks
> 


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Assefa Yewondwossen
Software Analyst

Email: assefa at dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056 (ext 14)
Fax:   (613) 565-0925
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