Dear CinGG users,
Does anybody want to taste something brand new and unusual? Here is the
patch attached:
cgg-blendalgebra.diff.gz
Apply this patch and rebuild CinGG. The only change is the addition of two
completely new video effects, Blend Algebra and Blend Program. The main
CinGG code is not affected, so applying the patch is harmless and cannot
break anything.
After applying the patch, and before executing `make', check that the new
created scripts plugins/blendalgebra/BlendAlgebraCompile.pl and
plugins/blendprogram/BlendProgramCompile.pl possess executable permissions.
After successful `make', don't forget to run `make install': without several
important files which must be installed, the new plugins cannot work.
Motivation
==========
Sometimes there appear again questions / complains regarding overlay
blending in Cinelerra, that something appears strange, or not exactly that
way as in Gimp (or in whatever), or not in that art the user needs.
Fighting such windmills does not seem worth while.
The idea here is to create a new specific plugin where the user could
program sufficiently short and simple blending algorithms according to his
requirements. And of course, without demanding from the user too much
programming skills.
Firstly I'd like to make a short introduction, a small demo what one can do
with the new features. The shortest demo projects are attached here, for
several longer ones I'll give the links to download them.
This development is already posted to CinGG bugtracker as BT670:
https://www.cinelerra-gg.org/bugtracker/view.php?id=670
To look on the following example functions, there is 'Edit...' button in the
respective plugin dialog, but you may need a text editor. By default, it is
`emacs', and nothing has to be done if it is installed. If not, you can set
your favorite editor via the corresponding environment variable, like those:
export CIN_EDITOR=kate
export CIN_EDITOR=nedit
export CIN_EDITOR='konsole -e vim'
If text editor is a console editor without its own GUI, it must be run from
some terminal emulator, like `xterm' or `konsole'.
To open editor from the plugin dialog, some function must be active at that
timeline position (its name in text field not empty). Currently, pressing
the 'Edit...' button on the empty function does nothing. Either select some
existing function first, or enter a name to create a new one from scratch.
Example 1.
----------
See ovl2.tar.gz in the attachment
Let's say, we are going to write our own implementation of the Arithmetic
Subtract overlay function, according to the formula from CinelerraGG manual.
Such a function, attached to the Blend Algebra plugin, could look as
follows.
------------------------------------------------------------------------
BLEND_ALGEBRA_INIT /* this is a required statement */
COLORSPACE_RGB /* our working color space, can be also YUV or HSV */
PARALLEL_SAFE /* can be safely parallelized */
REQUIRE_TRACKS(2) /* refuse to work if only one track is given */
BLEND_ALGEBRA_PROC /* this is a required statement */
#define s 1 /* mnemonics for source and destination */
#define d 0
R_OUT = R(s) - R(d); /* for red, green, blue, alpha: */
G_OUT = G(s) - G(d); /* result = source - destination */
B_OUT = B(s) - B(d);
A_OUT = A(s) - A(d);
BLEND_ALGEBRA_END /* this marks the end of our program */
------------------------------------------------------------------------
And here is an Arithmetic Addition variant, working on any number of tracks.
------------------------------------------------------------------------
BLEND_ALGEBRA_INIT
COLORSPACE_RGB
PARALLEL_SAFE
BLEND_ALGEBRA_PROC
int i;
R_OUT = G_OUT = B_OUT = A_OUT = 0; /* preinitialize results */
for (i=0; i<TOTAL_TRACKS; i++) /* repeat for all tracks */
{
R_OUT += R(i); /* accumulate sum for R,G,B,A */
G_OUT += G(i);
B_OUT += B(i);
A_OUT += A(i);
}
BLEND_ALGEBRA_END
------------------------------------------------------------------------
Blend Algebra functions are keyframable, i.e. switchable between plugin
keyframes. Untar the ovl2.tar.gz archive from the attachment, load the
ovl2.xml project and play it. You can see 30 different functions switched
one after another. The source files of the functions have the suffix '.ba'.
Example 2.
----------
Let's look on the following short Blend Algebra function:
------------------------------------------------------------------------
BLEND_ALGEBRA_INIT
COLORSPACE_YUV
PARALLEL_SAFE
REQUIRE_TRACKS(2)
BLEND_ALGEBRA_PROC
Y_OUT = (Y(0)-Y(1))/2+0.5;
U_OUT = V_OUT = 0;
A_OUT = 1;
BLEND_ALGEBRA_END
------------------------------------------------------------------------
What do you think this is? It is nothing else as the famous `ydiff'
program, written in less than 10 lines of code and working not externally,
but directly inside a Cinelerra plugin. Although this is not yet so
complete, the standard ydiff program has an argument to enhance or reduce
the difference effect, but we can easily add it here, too:
------------------------------------------------------------------------
BLEND_ALGEBRA_INIT
COLORSPACE_YUV
PARALLEL_SAFE
REQUIRE_TRACKS(2)
BLEND_ALGEBRA_PROC
Y_OUT = (Y(0)-Y(1))/2*exp((KEY_A-0.5)*14*M_LN2)+0.5;
U_OUT = V_OUT = 0;
A_OUT = 1;
BLEND_ALGEBRA_END
------------------------------------------------------------------------
Here we changed only the expression for Y, adding a factor which depends on
the KEY_A parameter in logarithmic scale. The KEY_A parameter itself is
interactively controlled by the opacity slider in the Blend Algebra plugin
dialog.
Good, the ydiff program additionally prints some statistics. This printout
can also be implemented by us, although the program becomes slightly more
complex:
------------------------------------------------------------------------
static int npix=0; /* these variables will accumulate statistics */
static float sum=0, sabs=0; /* parallelizing not possible here */
BLEND_ALGEBRA_INIT
COLORSPACE_YUV
REQUIRE_TRACKS(2)
printf ("sz=%8d err=%10g abs=%10g", npix, sum, sabs);
if (npix> 0) printf (" rel=%10g", sabs*256/npix);
printf ("\n"); /* here we print statistics in CGG console */
sum = sabs = 0; /* and clear accumulators for the next frame */
npix = 0;
BLEND_ALGEBRA_PROC
float diff;
diff = Y(0)-Y(1);
sum += diff; /* update accumulators */
sabs += ABS (diff);
npix ++;
Y_OUT = (Y(0)-Y(1))/2*exp((KEY_A-0.5)*14*M_LN2)+0.5;
U_OUT = V_OUT = 0; /* and make video track output */
A_OUT = 1;
BLEND_ALGEBRA_END
------------------------------------------------------------------------
The statistics is printed in the terminal emulator from which Cinelerra was
started.
You can look in the ydiff.tar.gz archive. In the project ydiff.xml there
are two identical tracks displaced by 1 frame. The ydiff.ba function from
the archive has the commented out line #define NO_PRINTOUT. It works slowly
because of statistics printout. If you uncomment this definition,
statistics will be switched off, the function will run parallelized,
noticeably faster.
The ydiff.tar.gz archive with this demo can be downloaded from CGG
bugtracker (2.5 Mb):
https://www.cinelerra-gg.org/bugtracker/file_download.php?file_id=995&type=bug
Example 3.
----------
Untar the example archive transitions.tar.gz and load the project
transitions.xml. It demonstrates how transition-like effects can be
imitated by a Blend Algebra function. Here, depending on the current value
of the opacity slider from plugin's dialog, interpolated between keyframes,
and the (X,Y) pixel coordinates, the function takes pixels from either track
#0 or track #1.
The transitions.tar.gz archive with this demo can be downloaded from CGG
bugtracker (2.5 Mb):
https://www.cinelerra-gg.org/bugtracker/file_download.php?file_id=996&type=bug
Example 4.
----------
Untar the archive swap.tar.gz and load the project swap.xml. Now there is
another companion plugin, Blend Program, with its function swap01.bp (ending
with the .bp suffix). This example resembles the preceding one which
imitated transition. The main difference here is that blend program does
not return a function result, but modifies any given tracks directly. The
program from this example swaps two tracks, along a transition controlled by
keyframable interpolated opacity parameter. To see the effect, the bottom
track is up-down reflected, and the top one has a mask applied, through
which one can see that the bottom track is also being changed.
The swap.tar.gz archive with this demo can be downloaded from CGG bugtracker
(2.5 Mb):
https://www.cinelerra-gg.org/bugtracker/file_download.php?file_id=997&type=bug
Example 5.
----------
The preceding example was perhaps somehow artificial demo, not too close to
reality. Let's now suggest another application which could be really
useful. Untar the ck.tar.gz example from the attachment and load firstly
the project ck.xml.
There is a still picture and a second track with solid white background on
bottom. The blend function attached is:
------------------------------------------------------------------------
BLEND_PROGRAM_INIT
COLORSPACE_HSV
PARALLEL_SAFE
BLEND_PROGRAM_PROC
if (ABS(H(0)-KEY_H)< KEY_A*100) A(0) *= SQR((H(0)-KEY_H)/KEY_A/100);
BLEND_PROGRAM_END
------------------------------------------------------------------------
It is a rather complete chromakey plugin, writable by user in only six lines
of code! Isn't it cool! With these two new small plugins one can do really
much! I do not know if a similar functionality exists in any other NLE.
Here if the 'Hue' component (in HSV color space) differs from that of the
key color defined in the plugin dialog less than by the amount scaled by the
opacity slider, the aplha component (the transparency) is set proportional
to the squared difference (completely transparent where the two Hues are
identical). You can open plugin dialog and turn the slider in it to the
left and right and see its effect.
Now load another project from here, ckbg.xml. Now there is only one track
with the same picture. Instead of the second one which contained the
background, there is one more Blend Program plugin attached, its function
generating the desired background by itlesf. The background color is set
via the color selection dialog of that second Blend Program plugin GUI.
========================================================================
Those who have realized that are not interested in the new features at all,
can stop reading here. Who has some interest to try, welcome to read the
more detailed README.blendalg description from attachment. As a starting
tutorial one could, for example, take some of the overlay functions, modify
it to calculate according some other formula and look what changes. Or take
the 'background' blend program and implement some dependency on PIX_X and/or
PIX_Y to convert solid background to a gradient.
If some details in the description attached look too difficult to
understand, don't bother, skip unclear sections - perhaps everything will
work fine also without reading them.
_______________________________________________________________________________
Georgy Salnikov
NMR Group
Novosibirsk Institute of Organic Chemistry
Lavrentjeva, 9, 630090 Novosibirsk, Russia
Phone +7-383-3307864
Email [email protected]
_______________________________________________________________________________
