1 files changed, 105 insertions, 0 deletions
diff --git a/Imaging/libImaging/RankFilter.c b/Imaging/libImaging/RankFilter.c
new file mode 100644
index 0000000..a0f13cd
--- /dev/null
+++ b/Imaging/libImaging/RankFilter.c
@@ -0,0 +1,105 @@
+/*
+ * The Python Imaging Library
+ * $Id: RankFilter.c 2929 2006-11-22 21:12:55Z fredrik $
+ *
+ * min, max, median filters
+ *
+ * history:
+ * 2002-06-08 fl    Created
+ *
+ * Copyright (c) Secret Labs AB 2002.  All rights reserved.
+ *
+ * See the README file for information on usage and redistribution.
+ */
+
+#include "Imaging.h"
+
+/* Fast rank algorithm (due to Wirth), based on public domain code
+   by Nicolas Devillard, available at http://ndevilla.free.fr */
+
+#define SWAP(type,a,b) { register type t=(a);(a)=(b);(b)=t; }
+
+#define MakeRankFunction(type)\
+static type Rank##type(type a[], int n, int k)\
+{\
+    register int i, j, l, m;\
+    register type x;\
+    l = 0; m = n-1;\
+    while (l < m) {\
+        x = a[k];\
+        i = l;\
+        j = m;\
+        do {\
+            while (a[i] < x) i++;\
+            while (x < a[j]) j--;\
+            if (i <= j) {\
+                SWAP(type, a[i], a[j]);\
+                i++; j--;\
+            }\
+        } while (i <= j);\
+        if (j < k) l = i;\
+        if (k < i) m = j;\
+    }\
+    return a[k];\
+}
+
+MakeRankFunction(UINT8)
+MakeRankFunction(INT32)
+MakeRankFunction(FLOAT32)
+
+Imaging
+ImagingRankFilter(Imaging im, int size, int rank)
+{
+    Imaging imOut = NULL;
+    int x, y;
+    int i, margin, size2;
+
+    if (!im || im->bands != 1 || im->type == IMAGING_TYPE_SPECIAL)
+	return (Imaging) ImagingError_ModeError();
+
+    if (!(size & 1))
+	return (Imaging) ImagingError_ValueError("bad filter size");
+
+    size2 = size * size;
+    margin = (size-1) / 2;
+
+    if (rank < 0 || rank >= size2)
+	return (Imaging) ImagingError_ValueError("bad rank value");
+
+    imOut = ImagingNew(im->mode, im->xsize - 2*margin, im->ysize - 2*margin);
+    if (!imOut)
+	return NULL;
+
+#define RANK_BODY(type) do {\
+    type* buf = malloc(size2 * sizeof(type));\
+    if (!buf)\
+        goto nomemory;\
+    for (y = 0; y < imOut->ysize; y++)\
+        for (x = 0; x < imOut->xsize; x++) {\
+            for (i = 0; i < size; i++)\
+                memcpy(buf + i*size, &IMAGING_PIXEL_##type(im, x, y+i),\
+                       size * sizeof(type));\
+            IMAGING_PIXEL_##type(imOut, x, y) = Rank##type(buf, size2, rank);\
+        }\
+} while (0)
+
+    if (im->image8)
+        RANK_BODY(UINT8);
+    else if (im->type == IMAGING_TYPE_INT32)
+        RANK_BODY(INT32);
+    else if (im->type == IMAGING_TYPE_FLOAT32)
+        RANK_BODY(FLOAT32);
+    else {
+        /* safety net (we shouldn't end up here) */
+        ImagingDelete(imOut);
+        return (Imaging) ImagingError_ModeError();
+    }
+    
+    ImagingCopyInfo(imOut, im);
+
+    return imOut;
+
+nomemory:
+    ImagingDelete(imOut);
+    return (Imaging) ImagingError_MemoryError();
+}