.TH BLIND-SPECTRUM 1 blind
.SH NAME
blind-spectrum - Transform a gradient into a spectrum
.SH SYNOPSIS
.B blind-spectrum
[-y]
[-z
.IR depth ]
.I spectrum-stream
.SH DESCRIPTION
.B blind-spectrum
reads a video from stdin, transforms it according
to a colour table and prints the resulting video
to stdout. The values of the colours, excluding
the alpha channel, in stdin, are truncated to
fit [0, 1]. The resulting values for each pixel
is used to look up a colour in
.I spectrum-stream
for the same frame, with linear interpolation.
That colour is used as the pixel's colour. The
alpha values of the looked up colour and the
pixel's original colour are multiplied, and the
product is used as the pixel's alpha value.
.P
When looking up colours in
.IR spectrum-stream ,
the value of the first channel (the X channel)
is multiplied by the width of the video in
.I spectrum-stream
less 1,
the product is the column in
.I spectrum-stream
that will be used (using interpolation for
none integer products), and the value of the first
channel (the Y channel) is multiplied by the height
of the video in
.I spectrum-stream
less 1, the product is the row in
.I spectrum-stream
that will be used.
.SH OPTIONS
.TP
.B -y
Rather than using the values of the three
colour channels to look up a colour in a
multidimensional table, the luma is used to
look up a value in a singledimensional table.
Which dimension is used does not matter; the
result is unspecified if the colour table
is multidimensional.
.TP
.BR -z \ \fIdepth\fP
For each frame in stdin,
.I depth
frames are read from
.IR spectrum-stream .
When looking up colours in
.IR spectrum-stream ,
the value of the third channel (the > channel)
is multiplied by
.I depth
less 1, the product is the frame
in this set of
.I depth
frames from
.I spectrum-stream
that will be used.
.SH SEE ALSO
.BR blind (7),
.BR blind-from-text (1),
.BR blind-arithm (1),
.BR blind-double-spectrum (1),
.BR blind-round-wave (1),
.BR blind-sawtooth-wave (1),
.BR blind-sine-wave (1)
.BR blind-sinc-wave (1),
.BR blind-triangular-wave (1),
.BR blind-cone-gradient (1),
.BR blind-linear-gradient (1),
.BR blind-radial-gradient (1),
.BR blind-spiral-gradient (1),
.BR blind-square-gradient (1)
.SH AUTHORS
Mattias Andrée
.RI < maandree@kth.se >