* median.c: use the libc's qsort to find the median value. Not really the

best method anyway (see the research notes on the wiki), but now X = 8
    is faster than the previous implementation's X = 6.

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2807 92316355-f0b4-4df1-b90c-862c8a59935f

pipi/filter/median.c

@@ -27,6 +27,11 @@
 #include "pipi.h"
 #include "pipi_internals.h"
 
+static int cmpint(void const *i1, void const *i2)
+{
+    return *(int const *)i1 > *(int const *)i2;
+}
+
 pipi_image_t *pipi_median(pipi_image_t *src, int radius)
 {
     return pipi_median_ext(src, radius, radius);
@@ -45,7 +50,7 @@ pipi_image_t *pipi_median_ext(pipi_image_t *src, int rx, int ry)
     pipi_pixels_t *srcp, *dstp;
     float *srcdata, *dstdata;
     double *list;
-    int x, y, w, h, i, j, k, size, gray;
+    int x, y, w, h, i, j, size, gray;
 
     w = src->w;
     h = src->h;
@@ -68,7 +73,6 @@ pipi_image_t *pipi_median_ext(pipi_image_t *src, int rx, int ry)
     {
         for(x = 0; x < w; x++)
         {
-            double tmp;
             double *parser = list;
 
             /* Make a list of neighbours */
@@ -90,41 +94,22 @@ pipi_image_t *pipi_median_ext(pipi_image_t *src, int rx, int ry)
                     }
                     else
                     {
-                        *parser++ = srcdata[4 * (y2 * w + x2)];
-                        *parser++ = srcdata[4 * (y2 * w + x2) + 1];
-                        *parser++ = srcdata[4 * (y2 * w + x2) + 2];
-                        *parser++ = srcdata[4 * (y2 * w + x2) + 3];
+                        parser[0] = srcdata[4 * (y2 * w + x2)];
+                        parser[size * 1] = srcdata[4 * (y2 * w + x2) + 1];
+                        parser[size * 2] = srcdata[4 * (y2 * w + x2) + 2];
+                        parser[size * 3] = srcdata[4 * (y2 * w + x2) + 3];
+                        parser++;
                     }
                 }
             }
 
             /* Sort the list */
-            for(i = 0; i < size; i++)
+            qsort(list, size, sizeof(int), cmpint);
+            if(!gray)
             {
-                for(j = 0; j < i; j++)
-                {
-                    if(gray)
-                    {
-                        if(list[i] < list[j])
-                        {
-                            tmp = list[i];
-                            list[i] = list[j];
-                            list[j] = tmp;
-                        }
-                    }
-                    else
-                    {
-                        for(k = 0; k < 4; k++)
-                        {
-                            if(list[4 * i + k] < list[4 * j + k])
-                            {
-                                tmp = list[4 * i + k];
-                                list[4 * i + k] = list[4 * j + k];
-                                list[4 * j + k] = tmp;
-                            }
-                        }
-                    }
-                }
+                qsort(list + size, size, sizeof(int), cmpint);
+                qsort(list + 2 * size, size, sizeof(int), cmpint);
+                qsort(list + 3 * size, size, sizeof(int), cmpint);
             }
 
             /* Store the median value */
@@ -134,10 +119,10 @@ pipi_image_t *pipi_median_ext(pipi_image_t *src, int rx, int ry)
             }
             else
             {
-                dstdata[4 * (y * w + x)] = list[size / 2 * 4];
-                dstdata[4 * (y * w + x) + 1] = list[size / 2 * 4 + 1];
-                dstdata[4 * (y * w + x) + 2] = list[size / 2 * 4 + 2];
-                dstdata[4 * (y * w + x) + 3] = list[size / 2 * 4 + 3];
+                dstdata[4 * (y * w + x)] = list[size / 2];
+                dstdata[4 * (y * w + x) + 1] = list[size / 2 + size * 1];
+                dstdata[4 * (y * w + x) + 2] = list[size / 2 + size * 2];
+                dstdata[4 * (y * w + x) + 3] = list[size / 2 + size * 3];
             }
         }
     }