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/*
* The Python Imaging Library
* $Id: ModeFilter.c 2134 2004-10-06 08:55:20Z fredrik $
*
* mode filter
*
* history:
* 2002-06-08 fl Created (based on code from IFUNC95)
* 2004-10-05 fl Rewritten; use a simpler brute-force algorithm
*
* Copyright (c) Secret Labs AB 2002-2004. All rights reserved.
*
* See the README file for information on usage and redistribution.
*/
#include "Imaging.h"
Imaging
ImagingModeFilter(Imaging im, int size)
{
Imaging imOut;
int x, y, i;
int xx, yy;
int maxcount;
UINT8 maxpixel;
int histogram[256];
if (!im || im->bands != 1 || im->type != IMAGING_TYPE_UINT8)
return (Imaging) ImagingError_ModeError();
imOut = ImagingNew(im->mode, im->xsize, im->ysize);
if (!imOut)
return NULL;
size = size / 2;
for (y = 0; y < imOut->ysize; y++) {
UINT8* out = &IMAGING_PIXEL_L(imOut, 0, y);
for (x = 0; x < imOut->xsize; x++) {
/* calculate histogram over current area */
/* FIXME: brute force! to improve, update the histogram
incrementally. may also add a "frequent list", like in
the old implementation, but I'm not sure that's worth
the added complexity... */
memset(histogram, 0, sizeof(histogram));
for (yy = y - size; yy <= y + size; yy++)
if (yy >= 0 && yy < imOut->ysize) {
UINT8* in = &IMAGING_PIXEL_L(im, 0, yy);
for (xx = x - size; xx <= x + size; xx++)
if (xx >= 0 && xx < imOut->xsize)
histogram[in[xx]]++;
}
/* find most frequent pixel value in this region */
maxpixel = 0;
maxcount = histogram[maxpixel];
for (i = 1; i < 256; i++)
if (histogram[i] > maxcount) {
maxcount = histogram[i];
maxpixel = (UINT8) i;
}
if (maxcount > 2)
out[x] = maxpixel;
else
out[x] = IMAGING_PIXEL_L(im, x, y);
}
}
ImagingCopyInfo(imOut, im);
return imOut;
}
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