From 6a3309663e4c02afcef25db80e912d95593d51bc Mon Sep 17 00:00:00 2001
From: sam <sam@92316355-f0b4-4df1-b90c-862c8a59935f>
Date: Mon, 4 Aug 2008 17:23:38 +0000
Subject: [PATCH]   * ordered.c: implement Bayer dithering (pretty trivial).

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2665 92316355-f0b4-4df1-b90c-862c8a59935f
---
 examples/dither.c     | 12 ++++----
 pipi/Makefile.am      |  1 +
 pipi/dither/ordered.c | 68 +++++++++++++++++++++++++++++++++++++++++++
 pipi/pipi.h           |  1 +
 4 files changed, 77 insertions(+), 5 deletions(-)
 create mode 100644 pipi/dither/ordered.c

diff --git a/examples/dither.c b/examples/dither.c
index 7bdd3e6..ece8206 100644
--- a/examples/dither.c
+++ b/examples/dither.c
@@ -32,17 +32,19 @@ int main(int argc, char *argv[])
 
     switch(atoi(argv[2]))
     {
-        case 5:
+        case 6:
             newimg = pipi_dbs(img); break;
-        case 4:
+        case 5:
             newimg = pipi_ostromoukhov(img, PIPI_SCAN_SERPENTINE); break;
-        case 3:
+        case 4:
             newimg = pipi_ostromoukhov(img, PIPI_SCAN_RASTER); break;
-        case 2:
+        case 3:
             newimg = pipi_floydsteinberg(img, PIPI_SCAN_SERPENTINE); break;
+        case 2:
+            newimg = pipi_floydsteinberg(img, PIPI_SCAN_RASTER); break;
         case 1:
         default:
-            newimg = pipi_floydsteinberg(img, PIPI_SCAN_RASTER); break;
+            newimg = pipi_dither_ordered(img); break;
     }
 
     pipi_free(img);
diff --git a/pipi/Makefile.am b/pipi/Makefile.am
index 7c4cbb8..8fdc448 100644
--- a/pipi/Makefile.am
+++ b/pipi/Makefile.am
@@ -31,6 +31,7 @@ libpipi_la_SOURCES = \
 	filter/blur.c \
 	filter/convolution.c \
 	dither/floydsteinberg.c \
+	dither/ordered.c \
 	dither/ostromoukhov.c \
 	dither/dbs.c \
 	$(NULL)
diff --git a/pipi/dither/ordered.c b/pipi/dither/ordered.c
new file mode 100644
index 0000000..def6508
--- /dev/null
+++ b/pipi/dither/ordered.c
@@ -0,0 +1,68 @@
+/*
+ *  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.
+ */
+
+/*
+ * ordered.c: Bayer ordered dithering functions
+ */
+
+#include "config.h"
+#include "common.h"
+
+#include "pipi.h"
+#include "pipi_internals.h"
+
+static const int kernel8x8[8 * 8] =
+{
+   0,  32,   8,  40,   2,  34,  10,  42,
+  48,  16,  56,  24,  50,  18,  58,  26,
+  12,  44,   4,  36,  14,  46,   6,  38,
+  60,  28,  52,  20,  62,  30,  54,  22,
+   3,  35,  11,  43,   1,  33,   9,  41,
+  51,  19,  59,  27,  49,  17,  57,  25,
+  15,  47,   7,  39,  13,  45,   5,  37,
+  63,  31,  55,  23,  61,  29,  53,  21,
+};
+
+pipi_image_t *pipi_dither_ordered(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;
+
+            p = srcdata[y * w + x];
+            q = p > (1. + kernel8x8[(y % 8) * 8 + (x % 8)]) / 65. ? 1. : 0.;
+            dstdata[y * w + x] = q;
+        }
+    }
+
+    return dst;
+}
+
diff --git a/pipi/pipi.h b/pipi/pipi.h
index 1db03dd..2d219e1 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -79,6 +79,7 @@ extern pipi_image_t *pipi_gaussian_blur_ext(pipi_image_t *,
                                             float, float, float, float);
 
 extern pipi_image_t *pipi_floydsteinberg(pipi_image_t *, pipi_scan_t);
+extern pipi_image_t *pipi_dither_ordered(pipi_image_t *);
 extern pipi_image_t *pipi_ostromoukhov(pipi_image_t *, pipi_scan_t);
 extern pipi_image_t *pipi_dbs(pipi_image_t *);
 extern void pipi_dither_24to16(pipi_image_t *);