how to measure alpha values

[Peter Wassink]

for a paper structure i needed to even out "alpha holes" in semi transparent area's.
i managed to to do this by merging a semitransparent layer using "Alpha diff mode while merging.
still figuring out the ammount of transparency was trial and error.
is there a way to messure the alpha value of a pixel?
i tried the coordinate panel but it only gives RGB values and no alpha.

[Fabrice]

Hello Peter,

I'm not sure to understand what you want to do, but I think that the "FX > Color > Histogram" may help. There is an alpha tab inside.

[Peter Wassink]

Hello Peter,

I'm not sure to understand what you want to do

i guess its a bit tricky to explain
but i need to close or "heal" holes in a layer that is not 100% opaque

so say i have a layer that is 50% transparent but it has parts that are 100 % transparent (the holes)
i now want to fill these 100% holes so the whole area is seamlessly 50% transparent.
this is possible with an alpha diffmerge but only if you know that the transparency value of the layer i need to fix is indeed 50%
thats why i was looking for a way to find out what % of transparency a pixel has ( what alpha value).

The Histogram FX seems to display a graph of the Alpha info in an image but i don't see how i can get a usefull opacvity% out of it.
I was thinking along the lines of the colorpicker but then an "alpha picker"
Feature request?

[ZigOtto]

not totally clear to me, but haven't you the RGBA values in your infobar when you roll your mouse (cursor) over the canvas ?

infobar.png (2.24 KiB) Viewed 7952 times

if you need the alpha info of a single layer, hide all others.
if not a solution for your specific case, you can consider to write a little script and get the "right" Alpha value,
using one of these commands (regarding your needs) :

Code: Select all

tv_PicColor
tv_GetPixelDisplay
tv_GetPixelLayer

Note that the returned A value is from 0 to 255, not in % opacity (0 to 100).

btw, I remember Manuel have done and shared (far ago) a george script called "PickColor+Alpha" or something,
notg sure, but maybe it's just what you 're looking for actually ...

[slowtiger]

It looks like it only shows the alpha of the selected layer? No need to hide the others.

[Peter Wassink]

not totally clear to me, but haven't you the RGBA values in your infobar when you roll your mouse (cursor) over the canvas ?

wow Thanks Zig,
a clear case of Doh!