ref: da7d6df6faf18e289fe0f3f61524dcc7fddeef18
dir: /appl/wm/mpeg/remap4.b/
implement Remap; include "sys.m"; include "mpegio.m"; Mpegi, YCbCr: import Mpegio; CLOFF: con 255; width, height, w2: int; out: array of byte; elum: array of int; clamp16 := array[CLOFF + 256 + CLOFF] of int; init(m: ref Mpegi) { width = m.width; height = m.height; w2 = width >> 1; out = array[w2 * height] of byte; elum = array[width + 1] of int; for (i := 0; i < CLOFF; i++) clamp16[i] = 0; for (i = 0; i < 256; i++) clamp16[i + CLOFF] = i >> 4; for (i = CLOFF + 256; i < CLOFF + 256 + CLOFF; i++) clamp16[i] = 255 >> 4; } 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 < w2; k++) { y := (256 - int Y[n++]) + elum[ex]; l := clamp16[y + CLOFF] << 4; 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 = clamp16[y + CLOFF]; out[m++] = byte (b | l); y -= l << 4; t = (3 * y) >> 4; elum[ex] = t + el; elum[ex + 1] += t; el = y - 3 * t; ex++; } } return out; }