Subject:
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Re: LDGlite and LPub (and maybe ldview?
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 14 Oct 2004 20:36:22 GMT
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Viewed:
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1409 times
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In lugnet.cad, Don Heyse wrote:
> In lugnet.cad, Steve Bliss wrote:
> Heh, maybe in ldview, but not in ldglite. You give me too much credit.
> I don't do real transparency for transparent parts. It's all dithered.
> And the only values I output to the alpha channel are fully transparent
> (with the png background color set to white) or completely opaque. Your
> caveat may come into play when an oversized image is sampled down
> though because that might mix the dithering in with the background.
That would change things.
> I'd better read up on png transparency though, because I don't know
> what's the point of setting the png background color to white.
That color is used when you display it in a program that doesn't have any better
color to use. In other words, if the image isn't put over some kind of
background, the color in the image is used.
> > Oh, and it probably also effects the antialiasing on all parts.
>
> I believe you're correct on this one. It looks OK on this antialiased
> png, generated with the default white background.
>
> http://brickshelf.com/cgi-bin/gallery.cgi?i=81648
Well, it's mostly right. But display it over a red background, and you'll see
that the antialiasing is actually updating the destination alpha on the whole
image. You get red bleed-through on the edge lines in the middle of the image,
as well as around the edges.
> But I don't know what it'll look like when done at 3x and then sampled
> down to 1x. I think that's the method used for the peeron images.
> Not sure about the ldraw part tracker...
I think that what it looks like will completely depend on how smart the program
is that does the resampling. Since the source image has all alpha at either 0%
or 100%, the background color shouldn't be used during the calculation of the
resampled color. So it might look fine. However, if the program blends all 4
channels blindly, then it won't look right.
--Travis
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Message has 1 Reply:
 | | Re: LDGlite and LPub (and maybe ldview?
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| (...) Eeek. I was just wondering about that. Do you have a link, or a quick html snippit. Is there a different opengl alpha blend fn that I should perhaps be using? I guess I'd better read up after all, opengl, and png. (...) Yeah. (20 years ago, 14-Oct-04, to lugnet.cad)
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Message is in Reply To:
| | Re: LDGlite and LPub (and maybe ldview?
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| (...) Heh, maybe in ldview, but not in ldglite. You give me too much credit. I don't do real transparency for transparent parts. It's all dithered. And the only values I output to the alpha channel are fully transparent (with the png background (...) (20 years ago, 14-Oct-04, to lugnet.cad)
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