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implement Remap;
include "sys.m";
include "mpegio.m";
Mpegi, YCbCr: import Mpegio;
CLOFF: con 255;
width, height, w4: int;
out: array of byte;
elum: array of int;
clamp4 := array[CLOFF + 256 + CLOFF] of int;
init(m: ref Mpegi)
{
width = m.width;
height = m.height;
w4 = width >> 2;
out = array[w4 * height] of byte;
elum = array[width + 1] of int;
for (i := 0; i < CLOFF; i++)
clamp4[i] = 0;
for (i = 0; i < 256; i++)
clamp4[i + CLOFF] = i >> 6;
for (i = CLOFF + 256; i < CLOFF + 256 + CLOFF; i++)
clamp4[i] = 255 >> 6;
}
remap(p: ref Mpegio->YCbCr): array of byte
{
Y := p.Y;
for (e := 0; e <= width; e++)
elum[e] = 0;
m := 0;
n := 0;
for (i := 0; i < height; i++) {
el := 0;
ex := 0;
for (k := 0; k < w4; k++) {
y := (256 - int Y[n++]) + elum[ex];
l := clamp4[y + CLOFF] << 6;
b := l;
y -= l;
t := (3 * y) >> 4;
elum[ex] = t + el;
elum[ex + 1] += t;
el = y - 3 * t;
ex++;
y = (256 - int Y[n++]) + elum[ex];
l = clamp4[y + CLOFF];
b |= l << 4;
y -= l << 6;
t = (3 * y) >> 4;
elum[ex] = t + el;
elum[ex + 1] += t;
el = y - 3 * t;
ex++;
y = (256 - int Y[n++]) + elum[ex];
l = clamp4[y + CLOFF];
b |= l << 2;
y -= l << 6;
t = (3 * y) >> 4;
elum[ex] = t + el;
elum[ex + 1] += t;
el = y - 3 * t;
ex++;
y = (256 - int Y[n++]) + elum[ex];
l = clamp4[y + CLOFF];
out[m++] = byte (b | l);
y -= l << 6;
t = (3 * y) >> 4;
elum[ex] = t + el;
elum[ex + 1] += t;
el = y - 3 * t;
ex++;
}
}
return out;
}
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