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- pk:{x@*<{x|-x}x-y}
- pre:{+/y*0^z@(!#z)+/:|x}
- pres:{g:+g@/:\:!g:(x[0;1];x[1])@\:=**x;({+/y*0^z@x-1}.*g;{+/x@'0^y@!#x}[pre.'1_g])}
- fldrow:{(e,*y;(*|y),'(e:z-n;n:x[0]@z:z+x[1][*y]%x[3]))}
- pr:{fldrow[x]/[(,0.0;(!0;!0)); z+x[2][y]%x[3]]}
- ediff:{|*|{(,'*|pr[x;*y;z]),'y}[x]/[(,&#*y;0#,!0);y]}
- setup:{l:(w:&0<y[1])-*+&^y[1];f:.[y[1];]'+w;pk[x],pres[(l;f)], y[0]}
- specs:!/+(("floyd-steinberg"
- (16;(0 0N 7
- 3 5 1)))
- ("sierra"
- (32;(0 0 0N 5 3
- 2 4 5 4 2
- 0 2 3 2 0)))
- ("sierraTwo"
- (16;(0 0 0N 4 3
- 1 2 3 2 1)))
- ("sierraLite"
- (4;(0 0N 2
- 1 1 0)))
- ("burkes"
- (32;(0 0 0N 8 4
- 2 4 8 4 2)))
- ("stucki"
- (42;(0 0 0N 8 4
- 2 4 8 4 2
- 1 2 4 2 1)))
- ("jarvis"
- (48;(0 0 0N 7 5
- 3 5 7 5 3
- 1 3 5 3 1)))
- ("atkinson"
- (8;(0 0N 1 1
- 1 1 1 0
- 0 1 0 0))))
- /
- Inspired by
- [[https://gist.github.com/0racle/f48586b6b2c05d13e3abbcb046e91dfb][0racle]]
- this is an implementation of several error diffusion dithering
- algorithms.
- Each spec is a divisor along with a distribution of the errors
- relative to the location of 0N.
- Each row is then scanned, collecting both output and errors
- (i.e. difference between the calculated input and the output). Error
- accumulated from a single previous row is calculated by pre. The
- function pres returns both a function which collects error for the
- current row and one which aggregates the calculated accumulated error
- for each previous row.
- The behavior of pres changes depending on the spec and are configured
- with setup. The first argument to setup is the range of output values
- the second is the spec which is parsed to produce pre and pres.
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