Image Composer - Saving .gifs with Image Composer (threshold/palettes..?)

Author

Saving .gifs with Image Composer (threshold/palettes..?)

Nicholas Savalas - http://savalas.tv

2006-03-22, 3:14 am

Can someone please explain to me the use of the threshold level when
saving .gifs in Image Composer? Help has left me baffled. I understand
the concept of transparency and Alpha color, but why is 191, rather
than 255, the default setting? What happens at 191 that MS chose it as
the default setting?

Also, transparent .gifs from IC usually aren't that good, and no
preview exists before saving. I can live with that. But the palette
choices - 216 colors - are Web-dithered (error diffusion - how?),
Web-solid, and Gray Ramp. Does someone know of a place to find better
palettes (target=web images) to load/use than the included ones? Thanks
in advance for any insight here.

Nicholas Savalas - http://savalas.tv

Walterius

2006-03-23, 6:14 pm

The only purpose of IC was to create gfx for the web. Attempts to make it do
otherwise usually fail. Unfortunately, it is such a good pgm that people
naturally want it to do more. You may wish to consider a more modern pgm
such as the $55 Real-Draw Pro, www.mediachance.com. PaintShop Pro is also
relatively inexpensive and does an excellent job with web gfx.

*Threshold* may have to do with the point at which IC decides that a pixel
is or is not transparent.

Walterius
Old, and mostly Photoshopping/PhotoDrawing in Fort Lauderdale.

Jan Kucera

2006-03-24, 6:17 am

Hi,
1) Threshold is some "level of tolerance" when deciding which colour
becomes transparent and which not. If you set it at maximum, more likely the
whole image will be transparent. If you set it zero, only and only the
pixels which colour is exact the selected one will be transparent.

2) Dithering method is the way, how the small number of colours in the
palette are used when trying to display a colour not in the palette. You can
see the difference mostly on gradients, just try it - with solid dithering,
the gradient splits in some areas with the same colour, in other dithering
methods, there are mixed together which results in more or less match of the
original picture. Microsoft ImageComposer can use Error Diffusion, Pattern,
and Random. Search a little on graphics algorithms to get know the
mathematic model behind them. If I can advise you, I use solid dithering on
small images, like icons with my user palette (later), and error diffusion
if a) I need to display more coloured and/or large images, like photos
(although you normally would use JPEG format), b) I have to match palette
which is already done.

3) You can preview what the image will look like, choosing the appreciate
palette on the toolbar (left to the zoom).

4) Microsoft ImageComposer saves your last used configuration of saving.
191 is not the default setting, you (or somebody else) choosed it before.
Default setting is 128, which is just half of the range. I do not find this
default value to be happy choosed, but since the Microsoft ImageComposer
saves your changes, it doesn't bother you.

5) Your images looks ugly you say. This can have two reasons. You are
setting transparent pixels you won't like to be. Set the threshold to zero.
I always set the threshold to zero to have the resulting image the same as I
see in the composition space. The second thing to do, if you do not have to
match any palette, is to create the palette on your own, which will use as
many colours as possible doblue click to match your image. Select the
sprite or sprites you are going to export as a gif. Double click the color
swatch (the window with current colour, mostly at the left side), a Color
Picker dialog will appear. Switch to Custom Palette tab. In the Create and
edit custom palettes group box, choose New. Type a name for the palette
which you like, choose 256 colours, and appreciate dithering method (this
can be later changed, while number of colours can't be), start with solid
one if you have simple small grapics without really true-colour alpa-leveled
stuff. Press OK, now you can see your new palette in the Color Picker, with
256 empty squares. You can manually choose the colours you would definetly
like to include in the pallete for some reason (by double clicking the
squares) and then press Generate Colors. Enter as many colours as you are
allowed to, mostly 256 if you didn't assign any explicitly, and choose
Generate from Selection. Press Add and you can see your 'optimized' for the
selection. If there remained any empty squares, just ignore it
(congratulations, all colours frome image where used and it will look
exactly as in the Compositino space; if you don't know anything about GIF
file format, you do not need to change the number of colours in order to
small down the file size). Well, that's it! Press OK, and in the colour
palette selector on the toolbar you can see how it will look like, to be
honest I rarely do that. While saving, choose the pallete you created,
select the transparent colour (mostly the background one, should be the
first), set the threshold to zero and tell me how are you satisfied. ;-)

6) Consider using another format than GIF, I would recomend you the PNG
one, which uses lossless compression, is (normally) true-coloured and has
separate alpha channel. Unfortunately, there is a bug in the Microsoft
Internet Explorer, which do not use the PNG transparency channel, and which
is fixed in version 7.

Feel free to ask if I can explain something clearer.

Thank you,
Jan Kucera

____________________________
I'm using Microsoft ImageComposer every day for almost ten years and never
needed to think of a change. The web graphics is only occasionally stuff I
do with it. It has about 10MB and can run without installation. If you are
going to buy any graphics product instead of it, please write me the reasons
for it.

"Nicholas Savalas - http://savalas.tv" <nick@savalas.tv> wrote in message
news:1143011520.826338.100180@v46g2000cwv.googlegroups.com...
> Can someone please explain to me the use of the threshold level when
> saving .gifs in Image Composer? Help has left me baffled. I understand
> the concept of transparency and Alpha color, but why is 191, rather
> than 255, the default setting? What happens at 191 that MS chose it as
> the default setting?
>
> Also, transparent .gifs from IC usually aren't that good, and no
> preview exists before saving. I can live with that. But the palette
> choices - 216 colors - are Web-dithered (error diffusion - how?),
> Web-solid, and Gray Ramp. Does someone know of a place to find better
> palettes (target=web images) to load/use than the included ones? Thanks
> in advance for any insight here.
>
> Nicholas Savalas - http://savalas.tv
>