Re: [Gimp-user] What happened to transparency after flatten?

2003-10-13 Thread Albert Wagner 
On Mon, 13 Oct 2003 17:49:02 +0200
Marco Wessel [EMAIL PROTECTED] wrote:
snip

Ah! That does it.  Thank you, Marco.

-- 
Life is an offensive, directed against the repetitious mechanism of the
Universe. 
--Alfred North Whitehead (1861-1947)
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Re: [Gimp-user] What happened to transparency after flatten?

2003-10-13 Thread Kevin Myers 
Hi Marco -

I've been working with some facets of digital images for a long time, but I
still don't completely understand everything about transparency.  In
particular, you mention one of the things here that I am confused about.
Could you please explain further exactly what transparency and alpha
channels have to do with each other?  Does the value of the alpha channel
provide the transparency level for each pixel, and if so, then what does
that have to do with alpha?  Also, how is level of transparency actually
applied in order compute the final display values for a pixel when a
semi-transparent pixel is overlaid onto an underlying non-transparent pixel?
Although the original question in this thread involved png files, I am more
interested in tiff files, but I suspect that essentially the same answer
applies to both.  Thanks!

s/KAM


- Original Message - 
From: Marco Wessel [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Monday, October 13, 2003 10:49 AM
Subject: Re: [Gimp-user] What happened to transparency after flatten?


 On Mon, Oct 13, 2003 at 10:32:13AM -0500, Albert Wagner wrote:
  I have several layered images developed for an animation. I built them
  using a white background for ease in drawing. All other layers were
  transparent.  For each I then deleted the background layer, flattened
  the image, and saved as *.png. However, the flattened image still had a
  white background, when I intended that it be transparent.  What did I do
  wrong?
 

 That's exactly what flatten is intended to do. If you want an alpha
channel
 in your png, just use save as a png without flattening. It'll ask you to
 merge the visible layers for the export because png can't handle them, and
 save a png just like you want it to: with alpha channel.

 Marco Wessel

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Re: [Gimp-user] What happened to transparency after flatten?

2003-10-13 Thread Marco Wessel 
On Mon, Oct 13, 2003 at 11:06:09AM -0500, Kevin Myers wrote:
 Hi Marco -
 
 I've been working with some facets of digital images for a long time, but I
 still don't completely understand everything about transparency.  In
 particular, you mention one of the things here that I am confused about.
 Could you please explain further exactly what transparency and alpha
 channels have to do with each other? 

First off -- unless you mean you want to see through parts of an image
entirely, you mean translucency. Transparent - invisible; translucent
- see-through.

The alpha channel is basically a channel just like red, green, and blue,
except that it determines the translucency of the pixel, instead of the
colour. 

 what does that have to do with alpha? 

I have no clue why they called it an alpha channel, if that's what you
mean.

 Also, how is level of transparency actually
 applied in order compute the final display values for a pixel when a
 semi-transparent pixel is overlaid onto an underlying non-transparent pixel?

While typing this email, I see sven has answered this.

 Although the original question in this thread involved png files, I am more
 interested in tiff files, but I suspect that essentially the same answer
 applies to both.  Thanks!
 

Both support alpha channels, yes.


Marco
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