* ordered.c: allow to rotate the dither pattern, using nearest-neighbour

rotation interpolation.

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2811 92316355-f0b4-4df1-b90c-862c8a59935f

pipi/context.c

@@ -104,11 +104,16 @@ int pipi_command(pipi_context_t *ctx, char const *cmd, ...)
             pipi_free(ctx->images[ctx->nimages - 2]);
             ctx->nimages--;
         }
-        else if(!strcmp(method, "ordered"))
+        else if(!strncmp(method, "ordered", 7))
         {
+            double angle = .0;
+            method = strchr(method, ':');
+            if(method)
+                angle = atof(method + 1);
             if(ctx->nimages < 2)
                 return -1;
-            dst = pipi_dither_ordered(ctx->images[ctx->nimages - 2], src);
+            dst = pipi_dither_ordered_ext(ctx->images[ctx->nimages - 2], src,
+                                          angle);
             pipi_free(ctx->images[ctx->nimages - 2]);
             ctx->nimages--;
         }

pipi/dither/ordered.c

@@ -20,22 +20,33 @@
 #include "common.h"
 
 #include <stdlib.h>
+#include <math.h>
 
 #include "pipi.h"
 #include "pipi_internals.h"
 
 pipi_image_t *pipi_dither_ordered(pipi_image_t *img, pipi_image_t *kernel)
 {
+    return pipi_dither_ordered_ext(img, kernel, 0.0);
+}
+
+pipi_image_t *pipi_dither_ordered_ext(pipi_image_t *img, pipi_image_t *kernel,
+                                      double angle)
+{
+    double sint, cost;
     pipi_image_t *dst;
     pipi_pixels_t *dstp, *kernelp;
     float *dstdata, *kerneldata;
-    int x, y, w, h, kw, kh;
+    int x, y, w, h, kx, ky, kw, kh;
 
     w = img->w;
     h = img->h;
     kw = kernel->w;
     kh = kernel->h;
 
+    cost = cos(angle * (M_PI / 180));
+    sint = sin(angle * (M_PI / 180));
+
     dst = pipi_copy(img);
     dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
     dstdata = (float *)dstp->pixels;
@@ -49,8 +60,11 @@ pipi_image_t *pipi_dither_ordered(pipi_image_t *img, pipi_image_t *kernel)
         {
             float p, q;
 
+            kx = (int)(cost * x - sint * y + 2 * w * h) % kw;
+            ky = (int)(cost * y + sint * x + 2 * w * h) % kh;
+
             p = dstdata[y * w + x];
-            q = p > kerneldata[(y % kh) * kw + (x % kw)] ? 1. : 0.;
+            q = p > kerneldata[ky * kw + kx] ? 1. : 0.;
             dstdata[y * w + x] = q;
         }
     }

pipi/pipi.h

@@ -182,6 +182,8 @@ extern pipi_image_t *pipi_reduce(pipi_image_t *, int, double const *);
 extern pipi_image_t *pipi_dither_ediff(pipi_image_t *, pipi_image_t *,
                                        pipi_scan_t);
 extern pipi_image_t *pipi_dither_ordered(pipi_image_t *, pipi_image_t *);
+extern pipi_image_t *pipi_dither_ordered_ext(pipi_image_t *, pipi_image_t *,
+                                             double);
 extern pipi_image_t *pipi_dither_halftone(pipi_image_t *, double, double);
 extern pipi_image_t *pipi_dither_random(pipi_image_t *);
 extern pipi_image_t *pipi_dither_ostromoukhov(pipi_image_t *, pipi_scan_t);