Re: converting to indexed and loss of quality
Thanks for everyone's replys. The solution works fine, although it's a shame you need to know your background for a transparent gif )-; I was wondering, is there a script-fu that would do this, i.e. add a layer fill with colour (parameter) merge visible layers select by colour (same parameter) remove selection If not, is that easy to do? Maybe I'll learn scripts. thanks Dave dave wrote: I've been using gimp for a short while now, and the one problem that keeps coming up is when I convert an RGB image to indexed, to save as a gif with a transparent background. I (think I) understand the issues with converting RGB colour to indexed, but what I don't understand is that I always seem to lose quality too (I guess that's somehow also a colour problem?) Even if I do nice simple fonts, in black, on a transparent background, I lose quality of the fonts on converting to indexed. I either lose nice smooth edges, or pixels within narrow parts of small fonts, or both. Why is this, and is there anything I can do about it? I need to do a lot of simple colour fonts with transparent backgrounds, so this is a real problem for me. many thanks Dave
Re: converting to indexed and loss of quality
On Sat, 5 Aug 2000, dave wrote: I've been using gimp for a short while now, and the one problem that keeps coming up is when I convert an RGB image to indexed, to save as a gif with a transparent background. I (think I) understand the issues with converting RGB colour to indexed, but what I don't understand is that I always seem to lose quality too (I guess that's somehow also a colour problem?) Even if I do nice simple fonts, in black, on a transparent background, I lose quality of the fonts on converting to indexed. I either lose nice smooth edges, or pixels within narrow parts of small fonts, or both. Why is this, and is there anything I can do about it? I need to do a lot of simple colour fonts with transparent backgrounds, so this is a real problem for me. many thanks Dave Since we are on topic of transperencyI use gimp-perl for scripting to draw several types of charts my main problem was to add a gif comment which is not possible by using gimp-1.1 so I came across Giftrans which allows me to add a comment as well as make the Image transperent with out the loss to the quality of the image. Any comments Chetan
converting to indexed and loss of quality
I've been using gimp for a short while now, and the one problem that keeps coming up is when I convert an RGB image to indexed, to save as a gif with a transparent background. I (think I) understand the issues with converting RGB colour to indexed, but what I don't understand is that I always seem to lose quality too (I guess that's somehow also a colour problem?) Even if I do nice simple fonts, in black, on a transparent background, I lose quality of the fonts on converting to indexed. I either lose nice smooth edges, or pixels within narrow parts of small fonts, or both. Why is this, and is there anything I can do about it? I need to do a lot of simple colour fonts with transparent backgrounds, so this is a real problem for me. many thanks Dave
Re: converting to indexed and loss of quality
On Sat, 5 Aug 2000, dave wrote: I've been using gimp for a short while now, and the one problem that keeps coming up is when I convert an RGB image to indexed, to save as a gif with a transparent background. I (think I) understand the issues with converting RGB colour to indexed, but what I don't understand is that I always seem to lose quality too (I guess that's somehow also a colour problem?) of course you will (though sometimes you can do this and make the picture look better like a jpeg that really should have been a png) play with the dithering options, and with how many color you remove. if you do it right (perhaps with a little touch up just before doing this) you can get good results with 3-6 bit color on these. the ones where you can use 4 bit color are usually obvious. Even if I do nice simple fonts, in black, on a transparent background, I lose quality of the fonts on converting to indexed. I either lose nice smooth edges, or pixels within narrow parts of small fonts, or both. Why is this, and is there anything I can do about it? I need to do a lot of simple colour fonts with transparent backgrounds, so this is a real problem for me. use the same color as the background of the image when you make the transperant font, what your losing here is the anti aliasing. you will still lose the anti aliasing, but it wont be noticiable (or as much). in a gif, color index 0 is always the one used at transperant. heres an example of using a 4 bit gif with antialiasing, http://necrodolly.necroerotic.org/lyrics/dandelion.html the necrodolly near the top has a black backround, giving it that "outline" of black (or how it looks "burnt"). the image under that is a 4 bit transperant gif. (which makes it look much smoother than 1 bit would) many thanks Dave
Re: converting to indexed and loss of quality
dave wrote: I've been using gimp for a short while now, and the one problem that keeps coming up is when I convert an RGB image to indexed, to save as a gif with a transparent background. I (think I) understand the issues with converting RGB colour to indexed, but what I don't understand is that I always seem to lose quality too (I guess that's somehow also a colour problem?) Even if I do nice simple fonts, in black, on a transparent background, I lose quality of the fonts on converting to indexed. I either lose nice smooth edges, or pixels within narrow parts of small fonts, or both. Why is this, and is there anything I can do about it? I need to do a lot of simple colour fonts with transparent backgrounds, so this is a real problem for me. I have the same problem so what I do is "Layers-Flatten Image" and then select the background color with "Select-By Color" with fuzziness 0 and remove it. I don't know if its a good solution, but for me it works. Regards niko
Re: converting to indexed and loss of quality
The gif format does not support a full alpha (transparency) channel, so if you want antialiasing, you need to know the color of your background first, merge it with your text, color-select the background color, then delete it. You should be left with the text surrounded by a little bit of the background color (actually closer to the text color). The png format does support a full alpha channel, although, only some browsers make use of this feature (mozilla and IE5.?). I don't rely on it, rather use one bit of transparency and keep the .xcf file around in case if I ever need to change the background color. I'm not getting in a debate as to what the best format is. Most antialiasing uses 8 to 16 colors, so you shouldn't get a loss in quality.
