blind-radial-gradient.1 - blind - suckless command-line video editing utility
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       blind-radial-gradient.1 (2181B)
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            1 .TH BLIND-RADIAL-GRADIENT 1 blind
            2 .SH NAME
            3 blind-radial-gradient - Generate a video with a radial gradient
            4 .SH SYNOPSIS
            5 .B blind-radial-gradient
            6 -w
            7 .I width
            8 -h
            9 .I height
           10 .SH DESCRIPTION
           11 .B blind-radial-gradient
           12 prints a video with a radial gradient to stdout,
           13 parameters for each from is read from each frame
           14 in stdin. The gradient is stored in all channels
           15 of the video.
           16 .P
           17 The video in stdin must contain exactly 2 or 3
           18 pixels per frame. The first pixel shall point to
           19 the beginning of the gradient (where the value is
           20 0) and the second pixel shall point to the end of
           21 the gradient (where the value is 1). In these
           22 pixels, the value of the first channel specifies
           23 the X-position and the value of the second
           24 channel specifies Y-position, the other channels
           25 are ignored.
           26 .P
           27 If there is a third pixel, in frames in stdin, it
           28 specified parameters to make the gradient elliptic
           29 or superelliptic. For a completely circular
           30 gradient its values should be 2, 2, and 1 for the
           31 first, second, and third channels, respectively;
           32 the fourth channel (the alpha channel) is ignored.
           33 If we name these values,
           34 .IR a ,
           35 .IR b ,
           36 and
           37 .IR m ,
           38 their is an imaginary superelliptic, on which the
           39 values of the gradient is 1, determined by the
           40 equation
           41 .RI || p ||^ a +|| r / m ||^ b =1,
           42 where
           43 .I p
           44 and
           45 .I r
           46 is the projection and rejection, respectively,
           47 of the normalised vector from beginning of the
           48 gradient to a pixel onto the vector from the
           49 beginning of the gradient to the end of the
           50 gradient.
           51 .SH NOTES
           52 Pixels after the end of the gradient have values
           53 larger than 1.
           54 .BR blind-*-wave (1)
           55 commands can be used to put all values between
           56 0 and 1.
           57 .SH OPTIONS
           58 .TP
           59 .BR -w " "\fIwidth\fP
           60 The width of the video, in pixels.
           61 .TP
           62 .BR -h " "\fIheight\fP
           63 The height of the video, in pixels.
           64 .SH SEE ALSO
           65 .BR blind (7),
           66 .BR blind-from-text (7),
           67 .BR blind-cone-gradient (1),
           68 .BR blind-linear-gradient (1),
           69 .BR blind-spiral-gradient (1),
           70 .BR blind-square-gradient (1),
           71 .BR blind-double-sine-wave (1),
           72 .BR blind-round-wave (1),
           73 .BR blind-sawtooth-wave (1),
           74 .BR blind-sinc-wave (1),
           75 .BR blind-sine-wave (1),
           76 .BR blind-triangular-wave (1),
           77 .BR blind-spectrum (1)
           78 .SH AUTHORS
           79 Mattias Andrée
           80 .RI < maandree@kth.se >