Semitransparent PNGs in Windows

**Twey** · 08-05-2006, 01:02 AM

I guess this is a graphics issue, although the solution, if one exists, is likely to be CSS...
A script I'm developing, at http://www.twey.co.uk/?q=rubberband, uses translucent PNG images for the background, for Opera support. This is fine on a white background, but under Windows, the demo version with a black background (http://www.twey.co.uk/includes/rubber/demo-inv.html) doesn't display the background over the black, although if one looks closely one can see its effects on the white text.

Is there any known fix for this?

**boogyman** · 08-05-2006, 01:28 AM

png files take up an immense amount of space, so I would suggest exporting it into a gif or jpg format

**Twey** · 08-05-2006, 01:38 AM

I would suggest reading the question before posting. If you know of a way to make GIF or JPG do alpha transparency, please do tell me.

Besides, PNG can have a substantially smaller filesize than GIF (although obviously not JPG), especially if run through something like Pngcrush (if you're using something like Photoshop, I'd guess; it doesn't seem to yield a great advantage over the GIMP's output).

Also, for what it's worth, I'm dealing with single-pixel images here, with a total filesize of 91 bytes each.

**mburt** · 08-05-2006, 01:55 AM

I've noticed though, that PNG's make the image a bit darker, which can kind of screw things up if your doing say, a graphic or something with the same background as the page. Which brings us back to the orignal issue. If you could make them transparent, that wouldn't be a problem

**Twey** · 08-05-2006, 02:21 AM

That's due to gamma correction, a rather kludged idea that went on to be poorly implemented

See http://hsivonen.iki.fi/png-gamma/ for some more details.

They are transparent :-\ That's not the problem. The problem is that on Windows, the black background isn't compensated for and they're totally invisible.

**blm126** · 08-05-2006, 03:15 AM

They look exactly the same to me.Checked in Opera,IE,and firefox because you didn't specify

**Twey** · 08-05-2006, 01:52 PM

It does look exactly the same, in every browser on Windows. Try viewing it in another operating system.

Maybe I should provide screenshots.

/EDIT: Here we go, this is what it looks like on Linux.
Here is a mock-up of how Windows displays it.
I don't know if Mac OS X will display it properly or not. I'd suspect so, but I'm not sure.