alpha0ps

These plugins are for alpha channel manipulation


Included are the following plugins:

alpha0ps:	shrink,grow,threshold and visualize alpha
alphagrad:	fill alpha channel with a gradient
alphaspot:	draw simple shapes into the alpha channel


Written by Marko Cebokli,  aug 2010,  and released under GNU GPL


RELEASE NOTES

** aug 2010
Version 0.1
"pre-alpha" (throw it out and see what happens... :-)



ALPHAOPS:

This plugin can shrink, grow, threshold and invert the alpha
channel. It is mainly intended to improve keying edges.
It can also display the alpha channel in various ways, to enable
quick assessment of the effect.
It is cascadable, so for example one can do a soft shrink first
and then threshold, which gives a slightly different result than
a hard shrink.

Parameters:

Display:
what to display. Choices are seven: Image, Alpha as gray, Gray+red,
Selection on black, Selection on gray, Selection on white and
Selection on checkers.
This is intended for monitoring during adjustment mostly. After
adjusting the parameters, it should be left on "Image", which lets
the unchanged input image through - this plugin is intended to
change only the alpha channel...

Display input alpha:
use input alpha for the display function above. (Check what alpha
we are getting on the input)

Operation:
select the operation to be done on the alpha channel. Currently
there are six choices: NO OP, Shave, Shrink hard, Shrink soft, Grow
hard, Grow soft, Threshold.
"Shave" tris to remove the "hairy" stuff, and also shrinks the selecton
a bit.
The "hard" operations introduce no new values to the alpha channel,
so if you have a "hard" key (only 0 and 255) it will stay that way.
The "soft" operations will introduce interpolated values, making
the edge softer.
NOTE: the shave, shrink and grow operations are quite slow, because they
do many conditional operations on each pixel.

Threshold:
this is only used for the Threshold operation.

Shrink/grow amount:
how far the shrinking/growing will extend.

Invert:
Inverts the input alpha channel, transparent will become opaque
and vice versa.




ALPHAGRAD:

This is a very simple plugin, that just fills the alpha channel
with a specified gradient.
It's purpose is to enable, together with alpha controlled color
manipulation, the use of graduated filters, for example like the
Cokin series #121, #122, #124, #150 and similar.
It is cascadable, allowing work with pre-existing alpha.

Parameters:

Position:
shift in the direction of gradient, for positioning the
gradient.

Transition width:
Width of the gradient slope between min and max values.

Tilt:
rotation of the gradient direction.

Min:
minimum value of the alpha channel, "before" the gradient.

Max:
maximum value of the alpha channel, "after" the gradient.

Operation:
slects between "Draw on clear", "Min", "Max", "Add" and "Subtract".
The last four options combine the drawn gradient with pre-existing
alpha.




ALPHASPOT

This is a simple plugin, that can draw a few simple shapes into
the alpha channel. It is intended for "in" and "out" masks in
keying, non-rectangular picture-in-picture, spotlight effects etc.
It is cascadable, allowing work with pre-existing alpha and
building of more complex shapes.

Parameters:

Shape:
selects between four shapes: rectangle, round, triangle and
diamond.

Pozx, pozy:
position of the drawn shape.

Sizx, sizy:
size of the drawn shape.

Tilt:
rotation of the drawn shape.

Transition width:
width of the soft border.

Min:
value of alpha outside of the shape.

Max:
value of alpha inside of the shape.

Operation:
slects between Draw on clear, Min, Max, Add, Subtract. The last
four options combine the drawn shape with pre-existing alpha.