Graphics: PNG (or whatever) to GIF (without losing quality)

robbbert · 03-25-2007, 02:50 PM

Hi, I have a set of PNG files and I'm trying to convert them to GIF (as Internet Explorer < 7.0 can't handle transparent PNGs).

I tried using "The" GIMP, Pixel Image Editor (in this case, I'd "optimized the image for GIF" before saving it), Krita, and ImageMagick.

The output in any case looks the same: scattered, pixelized.

As I remember, I'd experienced the same problem before, using Photoshop, Paint Shop Pro, and some other imaging software. Wait, some elder Photoshop version (4.0?) had an option to "export an optimized web image", and that worked roughly.

The problem is not the source format, or conversion, I think, but the output format. Anyways -

Any idea how to resolve my task?

Thanks

ilikejam · 03-25-2007, 03:38 PM

Hi.

Code:

convert img.png img.gif

should create a perfect copy. Not sure why it's not working for you, though.

Dave

robbbert · 03-26-2007, 12:09 PM

That's what I did, thanks.
Here's the image before and after...

That's hosted by imageshack.us BTW. Make sure your popup blocker is "on" ^^

ilikejam · 03-26-2007, 03:31 PM

Ah. The problem is that your image has transparent, but coloured areas. GIF can only do on-off transparency, which is what's causing the blocky-ness. Anything not 100% transparent is being tranformed into a colour.

If the background for the page is going to be white, then you can create a white 32x32 square (or whatever size your image is in general), and do

Code:

composite reloadxc6.png white.png reloadxc6.gif

and you'll have a smooth GIF image. You'll lose the transparency, though.

Dave

robbbert · 03-28-2007, 03:00 PM

Thanks!

Quote:

Originally Posted by ilikejam

Ah. The problem is that your image has transparent, but coloured areas. GIF can only do on-off transparency, which is what's causing the blocky-ness. Anything not 100% transparent is being tranformed into a colour.

Sorry, I didn't understand that, at all...

Quote:

Originally Posted by ilikejam

If the background for the page is going to be white, then you can create a white 32x32 square (or whatever size your image is in general), and do

Code:

composite reloadxc6.png white.png reloadxc6.gif

and you'll have a smooth GIF image. You'll lose the transparency, though.

Losing transparency would not be an option, unless transparency could be added again.

Thanks again

Zention · 03-28-2007, 03:07 PM

PNG has an alpha channel; blending colours with background.

GIF has transparency; showing background colour.

The places where the alpha channel is being used to blend a colour with the colour below (alpha channel) are problematic should it go to the colour or become transparent, that is the dilemma when converting to gif.

I am fairly sure IE7 supports png now.

But, there are some posts pertaining to it being a bit of a scam.

Gimp is slightly better at a default conversion.

I am sure there are workarounds for IE7 though.