From 302ce37f8e0f0bb71fee221318382eeb29d182e2 Mon Sep 17 00:00:00 2001
From: sam <sam@92316355-f0b4-4df1-b90c-862c8a59935f>
Date: Sun, 3 Aug 2008 03:31:20 +0000
Subject: [PATCH] * ostromoukhov.c: Ostromoukhov's simple error diffusion
algorithm.
git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2654 92316355-f0b4-4df1-b90c-862c8a59935f
---
examples/dither.c | 9 ++-
pipi/Makefile.am | 1 +
pipi/dither/ostromoukhov.c | 119 +++++++++++++++++++++++++++++++++++++
pipi/pipi.h | 1 +
4 files changed, 127 insertions(+), 3 deletions(-)
create mode 100644 pipi/dither/ostromoukhov.c
diff --git a/examples/dither.c b/examples/dither.c
index 47a63a9..463cf70 100644
--- a/examples/dither.c
+++ b/examples/dither.c
@@ -17,8 +17,9 @@ int main(int argc, char *argv[])
fprintf(stderr, "%s: too few arguments\n", argv[0]);
fprintf(stderr, "Usage: %s <src> <method> <dest>\n", argv[0]);
fprintf(stderr, "Where <method> is one of:\n");
- fprintf(stderr, " 1 Floyd-Steinberg\n");
- fprintf(stderr, " 2 Direct binary search\n");
+ fprintf(stderr, " 1 Floyd-Steinberg (serpentine)\n");
+ fprintf(stderr, " 2 Ostromoukhov (serpentine)\n");
+ fprintf(stderr, " 3 Direct binary search\n");
return EXIT_FAILURE;
}
@@ -30,8 +31,10 @@ int main(int argc, char *argv[])
switch(atoi(argv[2]))
{
- case 2:
+ case 3:
newimg = pipi_dbs(img); break;
+ case 2:
+ newimg = pipi_ostromoukhov(img); break;
case 1:
default:
newimg = pipi_floydsteinberg(img); break;
diff --git a/pipi/Makefile.am b/pipi/Makefile.am
index 83e69a3..daae164 100644
--- a/pipi/Makefile.am
+++ b/pipi/Makefile.am
@@ -30,6 +30,7 @@ libpipi_la_SOURCES = \
$(codec_sources) \
filter/blur.c \
dither/floydsteinberg.c \
+ dither/ostromoukhov.c \
dither/dbs.c \
$(NULL)
libpipi_la_CFLAGS = $(codec_cflags)
diff --git a/pipi/dither/ostromoukhov.c b/pipi/dither/ostromoukhov.c
new file mode 100644
index 0000000..ce7d9f7
--- /dev/null
+++ b/pipi/dither/ostromoukhov.c
@@ -0,0 +1,119 @@
+/*
+ * libpipi Proper image processing implementation library
+ * Copyright (c) 2004-2008 Sam Hocevar <sam@zoy.org>
+ * All Rights Reserved
+ *
+ * $Id$
+ *
+ * This library is free software. It comes without any warranty, to
+ * the extent permitted by applicable law. You can redistribute it
+ * and/or modify it under the terms of the Do What The Fuck You Want
+ * To Public License, Version 2, as published by Sam Hocevar. See
+ * http://sam.zoy.org/wtfpl/COPYING for more details.
+ */
+
+/*
+ * ostromoukhov.c: Ostromoukhov dithering functions
+ *
+ * This module implements Ostromoukhov's simple error diffusion algorithm,
+ * as introduced in the paper "A Simple and Efficient Error-Diffusion
+ * Algorithm", Proceedings of SIGGRAPH 2001, in ACM Computer Graphics,
+ * Annual Conference Series, pp. 567--572, 2001.
+ *
+ * TODO: the table is actually a piecewise linear function, so it should
+ * be easy to change it into something that works perfectly with floats.
+ */
+
+#include "config.h"
+#include "common.h"
+
+#include "pipi.h"
+#include "pipi_internals.h"
+
+static int const table[][3] =
+{
+ {13, 0, 5}, {13, 0, 5}, {21, 0, 10}, {7, 0, 4},
+ {8, 0, 5}, {47, 3, 28}, {23, 3, 13}, {15, 3, 8},
+ {22, 6, 11}, {43, 15, 20}, {7, 3, 3}, {501, 224, 211},
+ {249, 116, 103}, {165, 80, 67}, {123, 62, 49}, {489, 256, 191},
+ {81, 44, 31}, {483, 272, 181}, {60, 35, 22}, {53, 32, 19},
+ {237, 148, 83}, {471, 304, 161}, {3, 2, 1}, {481, 314, 185},
+ {354, 226, 155}, {1389, 866, 685}, {227, 138, 125}, {267, 158, 163},
+ {327, 188, 220}, {61, 34, 45}, {627, 338, 505}, {1227, 638, 1075},
+ {20, 10, 19}, {1937, 1000, 1767}, {977, 520, 855}, {657, 360, 551},
+ {71, 40, 57}, {2005, 1160, 1539}, {337, 200, 247}, {2039, 1240, 1425},
+ {257, 160, 171}, {691, 440, 437}, {1045, 680, 627}, {301, 200, 171},
+ {177, 120, 95}, {2141, 1480, 1083}, {1079, 760, 513}, {725, 520, 323},
+ {137, 100, 57}, {2209, 1640, 855}, {53, 40, 19}, {2243, 1720, 741},
+ {565, 440, 171}, {759, 600, 209}, {1147, 920, 285}, {2311, 1880, 513},
+ {97, 80, 19}, {335, 280, 57}, {1181, 1000, 171}, {793, 680, 95},
+ {599, 520, 57}, {2413, 2120, 171}, {405, 360, 19}, {2447, 2200, 57},
+ {11, 10, 0}, {158, 151, 3}, {178, 179, 7}, {1030, 1091, 63},
+ {248, 277, 21}, {318, 375, 35}, {458, 571, 63}, {878, 1159, 147},
+ {5, 7, 1}, {172, 181, 37}, {97, 76, 22}, {72, 41, 17},
+ {119, 47, 29}, {4, 1, 1}, {4, 1, 1}, {4, 1, 1},
+ {4, 1, 1}, {4, 1, 1}, {4, 1, 1}, {4, 1, 1},
+ {4, 1, 1}, {4, 1, 1}, {65, 18, 17}, {95, 29, 26},
+ {185, 62, 53}, {30, 11, 9}, {35, 14, 11}, {85, 37, 28},
+ {55, 26, 19}, {80, 41, 29}, {155, 86, 59}, {5, 3, 2},
+ {5, 3, 2}, {5, 3, 2}, {5, 3, 2}, {5, 3, 2},
+ {5, 3, 2}, {5, 3, 2}, {5, 3, 2}, {5, 3, 2},
+ {5, 3, 2}, {5, 3, 2}, {5, 3, 2}, {5, 3, 2},
+ {305, 176, 119}, {155, 86, 59}, {105, 56, 39}, {80, 41, 29},
+ {65, 32, 23}, {55, 26, 19}, {335, 152, 113}, {85, 37, 28},
+ {115, 48, 37}, {35, 14, 11}, {355, 136, 109}, {30, 11, 9},
+ {365, 128, 107}, {185, 62, 53}, {25, 8, 7}, {95, 29, 26},
+ {385, 112, 103}, {65, 18, 17}, {395, 104, 101}, {4, 1, 1}
+};
+
+pipi_image_t *pipi_ostromoukhov(pipi_image_t *src)
+{
+ pipi_image_t *dst;
+ pipi_pixels_t *srcp, *dstp;
+ float *srcdata, *dstdata;
+ int x, y, w, h;
+
+ w = src->w;
+ h = src->h;
+
+ srcp = pipi_getpixels(src, PIPI_PIXELS_Y_F);
+ srcdata = (float *)srcp->pixels;
+
+ dst = pipi_new(w, h);
+ dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
+ dstdata = (float *)dstp->pixels;
+
+ for(y = 0; y < h; y++)
+ {
+ for(x = 0; x < w; x++)
+ {
+ float p, q, e;
+ int x2, s, i;
+
+ x2 = (y & 1) ? x : w - 1 - x;
+ s = (y & 1) ? 1 : -1;
+
+ p = srcdata[y * w + x2];
+ q = p < 0.5 ? 0. : 1.;
+ dstdata[y * w + x2] = q;
+
+ e = p - q;
+ i = p * 255.9999;
+ if(i > 127) i = 255 - i;
+ if(i < 0) i = 0; /* XXX: no "else" here */
+ e /= table[i][0] + table[i][1] + table[i][2];
+
+ if(x < w - 1)
+ srcdata[y * w + x2 + s] += e * table[i][0];
+ if(y < h - 1)
+ {
+ if(x > 0)
+ srcdata[(y + 1) * w + x2 - s] += e * table[i][1];
+ srcdata[(y + 1) * w + x2] += e * table[i][2];
+ }
+ }
+ }
+
+ return dst;
+}
+
diff --git a/pipi/pipi.h b/pipi/pipi.h
index d4b3fbf..d95b14b 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -69,6 +69,7 @@ extern pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *,
float, float, float, float);
extern pipi_image_t *pipi_floydsteinberg(pipi_image_t *);
+extern pipi_image_t *pipi_ostromoukhov(pipi_image_t *);
extern pipi_image_t *pipi_dbs(pipi_image_t *);
extern void pipi_dither_24to16(pipi_image_t *);