Wish List for V12

[pauland]

Alpha channel is basically just a mask channel.

That depends on what the file format is. It's a true mask for Gif, but not at all for PNG, where there are discrete values for transparency.

[handrawn]

Well, the article actually substantiates my claim that there is a difference between an alpha channel and a layer that has transparency.

and the transparency that has been been requested by both ponny myself and others, and referenced by paul, is therefore an alpha channel?

I do not really care, just so long as I can define colour attribute of an object in alpha as well as rgb/cmyk whatever, not just apply transparency directly to the object only...

[theinonen]

GIF file only has 1-bit mask, so basically each pixel can have 2 values (on/off). 8-bit alpha mask has byte per pixel, so each pixel can have 256 different values (0-255).


Idea is still the same, white is solid and black transparent.

[pauland]

GIF file only has 1-bit mask, so basically each pixel can have 2 values (on/off). 8-bit alpha mask has byte per pixel, so each pixel can have 256 different values (0-255).


Idea is still the same, white is solid and black transparent.

Yes, but where were we discussing GIFs?

[theinonen]

File format is not really relevant.

Little example:

Rendered targa image with alpha channel. Lens has alpha of 0.5 and everything else 1.

Colour channels:

Alpha Channel:

Looks like this with both of those:


I can load the PNG image to olden but golden RISC OS image composition software and alpha channel automatically goes to mask layer (blend mask). It has one problem as the shadow is visible in lens and missing from the background where it will be inserted.

Easily fixed with another mask in shadowmask layer, and the image now has shadow.


Finished image:

[pauland]

I understand what a mask is. Having a binary marker acting as a mask is not the same as having an alpha channel providing a variable amount of transparency.

While an alpha channel can act as a mask, the discussion was about variable transparency applied to color rather than a clipping effect.

[theinonen]

I believe the main use of alpha channel is to control how images are inserted over background graphics.

But now I am off to get shower and start getting ready for half marathon, that I will be running in few hours.

[pauland]

Have a great run!

[handrawn]

@theinonen

some [especially earlier] programs automatically put transparency into a masking layer because that is the only way they can handle it, there is no transparency rendered in the UI [I should have though of that earlier then I might not have mis-understood what Gare was saying]

it makes sense maybe to think of alpha as masking when the transparency options are only two: its visible or it's not, and that is all the program UI can do

but in a file where the alpha channel has a full range of transparency from 0-254, just like the RGB, then there is no reason to treat it any differently to the other channels if the program UI will support it

masking is a function; not an attribute

I believe the main use of alpha channel is to control how images are inserted over background graphics.

and would it not be great to be able to do this by adjusting the opacity [transparency] of the colour directly?

Have a great run!

absolutely !

[amoore]

Since v12 has now been released as 365, I'm closing this thread. You can post your suggestions in the new thread for 365.