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.TH BLIND-RADIAL-GRADIENT 1 blind
.SH NAME
blind-radial-gradient - Generate a video with a radial gradient
.SH SYNOPSIS
.B blind-radial-gradient
-w
.I width
-h
.I height
.SH DESCRIPTION
.B blind-radial-gradient
prints a video with a radial gradient to stdout,
parameters for each from is read from each frame
in stdin. The gradient is stored in all channels
of the video.
.P
The video in stdin must contain exactly 2 or 3
pixels per frame. The first pixel shall point to
the beginning of the gradient (where the value is
0) and the second pixel shall point to the end of
the gradient (where the value is 1). In these
pixels, the value of the first channel specifies
the X-position and the value of the second
channel specifies Y-position, the other channels
are ignored.
.P
If there is a third pixel, in frames in stdin, it
specified parameters to make the gradient elliptic
or superelliptic. For a completely circular
gradient its values should be 2, 2, and 1 for the
first, second, and third channels, respectively;
the fourth channel (the alpha channel) is ignored.
If we name these values,
.IR a ,
.IR b ,
and
.IR m ,
their is an imaginary superelliptic, on which the
values of the gradient is 1, determined by the
equation
.RI || p ||^ a +|| r / m ||^ b =1,
where
.I p
and
.I r
is the projection and rejection, respectively,
of the normalised vector from beginning of the
gradient to a pixel onto the vector from the
beginning of the gradient to the end of the
gradient.
.SH NOTES
Pixels after the end of the gradient have values
larger than 1.
.BR blind-*-wave (1)
commands can be used to put all values between
0 and 1.
.SH OPTIONS
.TP
.BR -w " "\fIwidth\fP
The width of the video, in pixels.
.TP
.BR -h " "\fIheight\fP
The height of the video, in pixels.
.SH SEE ALSO
.BR blind (7),
.BR blind-from-text (7),
.BR blind-double-sine-wave (1),
.BR blind-round-wave (1),
.BR blind-sawtooth-wave (1),
.BR blind-sinc-wave (1),
.BR blind-sine-wave (1),
.BR blind-triangular-wave (1),
.BR blind-spectrum (1),
.BR blind-cone-gradient (1),
.BR blind-linear-gradient (1),
.BR blind-spiral-gradient (1),
.BR blind-square-gradient (1)
.SH AUTHORS
Mattias Andrée
.RI < maandree@kth.se >
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