Re: Graphic converter query - transparency

On 2008-06-29 04:45:01 +0100, real-address-in-sig@[EMAIL PROTECTED]
 
(Rowland McDonnell) said:

> Woody <usenet@[EMAIL PROTECTED]
> wrote:
> 
>> Rowland McDonnell <real-address-in-sig@[EMAIL PROTECTED]
> wrote:
>> 
>>> Woody <usenet@[EMAIL PROTECTED]
> wrote:
>>> 
>>>> Rowland McDonnell <real-address-in-sig@[EMAIL PROTECTED]
> wrote:
>>>> 
>>>>> It's a question I would have thought the manual would help me with,
but
>>>>> it seems not.
>>>>> 
>>>>> Can anyone tell me how to make a (currently white) area around the
>>>>> outside of an image into a transparent region using Graphic
Converter?
>>>> 
>>>> Although not a user of graphic converter, assuming it works in a
>>>> similarish way to other things, you can only change an area to
>>>> transparent if you want to make a gif, which I assume you don't if
you
>>>> are making an icon.
>>> 
>>> I dunno - I recall icons with transparent (missing, more like) bits
>>> under < OS X, so why can't I have 'em with OS X?
>> 
>> Well, you can, but that isn't what the finder uses for transparent
>> images (I don't think).
> 
> Well, with ResEdit, you could define a mask to blank off regions of the
> icon square that you didn't want to count as `part of the icon'.
> 
> Sometimes, this mask was used in an annoying fa****on so that the icon
> had holes in it thus making it hard to click.
> 
> Sounds like `equivalent to transparency' to me - and one would assume,
> in a sensible world, that the Finder would interpret transparent parts
> of an image given to it to use as an icon as `masked off bits' in that
> fa****on.

Finder still does, but not in general.

What you're describing is an image with a 1-bit mask, and that's either 
done by providing a 1-bit image as part of the icon file or by 
indicating which colour in the full icon is to be the mask.

Finder and OS X still use icon with 1-bit masks, but in general you 
need to provide icons with 8-bit masks because they're needed by the 
Dock. The mask is treated as grey-scale, where black is equivalent to 
"don't show" or "transparent", white is "show" or "100% opaque", and 
the other values give a smooth change between the two.

Another name for the mask is alpha channel.

Good luck with getting transparency working in any sane way with 
Graphic Converter. Last time I tried it was quite hard to make GC do 
anything approaching the right thing, or what I wanted.

Cheers,

Chris