nanogui: PNG support


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Subject: RE: [nanogui] PNG Support
From: Fabrice Gautier ####@####.####
Date: 19 Sep 2002 04:48:07 -0000
Message-Id: <B1F6452C89AFD411AE0800A0CC734C239DBD2D@EMAIL1>

I've not done a thorought investigation, but i think there is a bug.

In the current code, if i try to display an 8bit PNG image, the output is
compressed toward the left. I would says its compressed by a factor of 3. So
my guess is that somehow the decoding onl output 8 bit samples but nanoX
think its 24bits sample...

If i change pimage->bpp=24 to pimage->bpp=8 in LoadPNG then the size is
okay.


-- 
Fabrice Gautier, 
####@####.####


> -----Original Message-----
> From: Jordan Crouse ####@####.####
> Sent: Wednesday, September 18, 2002 12:36 PM
> To: Fabrice Gautier
> Cc: ####@####.####
> Subject: Re: [nanogui] PNG Support
> 
> 
> The image will be appropriately converted to the correct bit 
> depth when it is written to the screen, so we maintain an 
> internal representation of 24 bits for simplicity.
> 
> In your case, you may see an issue, depending on how well 
> Microwindows and the PNG library match your colors. The PNG 
> library is intelligent enough to understand the palletized 
> entries, so even though we are in 24 bit mode, the colors 
> should still stay true.  However, when we actually draw the 
> image, the colors will be matched to the internal 
> Microwindows palette which may or may not have the correct 
> colors.   At 8 bit depth, you should be OK, but be prepared 
> for colors to be a bit off from what you expected.
> 
> Jordan
> 
> On Wed, 18 Sep 2002 11:57:03 -0700
> Fabrice Gautier ####@####.#### wrote:
> 
> > Hi,
> > 
> > It seems that PNG images are always decoded as 24bpp 
> images. Am i right or
> > did i missed something?
> > 
> > Since I only have 8 bit display, and I use only 8bpp 
> palletized PNG I'd
> > rather have then as 8bpp images...
> > 
> > 
> > -- 
> > Fabrice Gautier, 
> > ####@####.####
> > 
> > 
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> > For additional commands, e-mail: ####@####.####
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> 

Previous by date: 19 Sep 2002 04:48:07 -0000 湘葩: [nanogui] display BMP file on iPAQ, ??宏
Next by date: 19 Sep 2002 04:48:07 -0000 Re: PNG Support, Greg Haerr
Previous in thread: 19 Sep 2002 04:48:07 -0000 Re: PNG Support, Jordan Crouse
Next in thread: 19 Sep 2002 04:48:07 -0000 Re: PNG Support, Greg Haerr


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