blind-radial-gradient.1 (2181B)
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 >