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/*
* GIMP CVS: "|Id: sharpen.c,v 1.23.2.1 2001/01/12 13:15:10 neo Exp |"
*
* Sharpen filters for The GIMP -- an image manipulation program
*
* Copyright 1997-1998 Michael Sweet (mike@easysw.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Contents:
*
* sharpen() - Sharpen an image using a median filter.
* rgb_filter() - Sharpen RGB pixels.
*
* Revision History:
*
* See GIMP ChangeLog
*/
#include <stdlib.h>
#include <string.h>
#include "sharpen.h"
#define new(ctype, ccount) calloc(ccount, sizeof(ctype))
static void
compute_luts (int sharpen_percent, int *pos_lut, int *neg_lut )
{
int i; /* Looping var */
int fact; /* 1 - sharpness */
fact = 100 - sharpen_percent;
if (fact < 1)
fact = 1;
for (i = 0; i < 256; i ++)
{
pos_lut[i] = (800 * i) / fact;
neg_lut[i] = (4 + pos_lut[i] - (i << 3)) >> 3;
};
}
/** 'rgb_filter()' - Sharpen RGB pixels. **/
static void rgb_filter (int width, /* I - Width of line in pixels */
int *pos_lut,
int *neg_lut,
unsigned char *src, /* I - Source line */
unsigned char *dst, /* O - Destination line */
long int *neg0, /* I - Top negative coefficient line */
long int *neg1, /* I - Middle negative coefficient line */
long int *neg2) /* I - Bottom negative coefficient line */
{
long int pixel; /* New pixel value */
*dst++ = *src++;
*dst++ = *src++;
*dst++ = *src++;
width -= 2;
while (width > 0)
{
pixel = (pos_lut[*src++] - neg0[-3] - neg0[0] - neg0[3] -
neg1[-3] - neg1[3] -
neg2[-3] - neg2[0] - neg2[3]);
pixel = (pixel + 4) >> 3;
if (pixel < 0)
*dst++ = 0;
else if (pixel < 255)
*dst++ = pixel;
else
*dst++ = 255;
pixel = (pos_lut[*src++] - neg0[-2] - neg0[1] - neg0[4] -
neg1[-2] - neg1[4] -
neg2[-2] - neg2[1] - neg2[4]);
pixel = (pixel + 4) >> 3;
if (pixel < 0)
*dst++ = 0;
else if (pixel < 255)
*dst++ = pixel;
else
*dst++ = 255;
pixel = (pos_lut[*src++] - neg0[-1] - neg0[2] - neg0[5] -
neg1[-1] - neg1[5] -
neg2[-1] - neg2[2] - neg2[5]);
pixel = (pixel + 4) >> 3;
if (pixel < 0)
*dst++ = 0;
else if (pixel < 255)
*dst++ = pixel;
else
*dst++ = 255;
neg0 += 3;
neg1 += 3;
neg2 += 3;
width --;
};
*dst++ = *src++;
*dst++ = *src++;
*dst++ = *src++;
}
/** 'sharpen()' - Sharpen an image using a convolution filter. **/
void sharpen(int width, int height,
unsigned char *src_region, unsigned char *dest_region,
int sharpen_percent
) {
unsigned char *src_rows[4], /* Source pixel rows */
*src_ptr, /* Current source pixel */
*dst_row; /* Destination pixel row */
long int *neg_rows[4], /* Negative coefficient rows */
*neg_ptr; /* Current negative coefficient */
int i, /* Looping vars */
y, /* Current location in image */
row, /* Current row in src_rows */
count, /* Current number of filled src_rows */
pitch; /* Byte width of the image */
int img_bpp=3; /* Bytes-per-pixel in image */
int neg_lut[256]; /* Negative coefficient LUT */
int pos_lut[256]; /* Positive coefficient LUT */
compute_luts (sharpen_percent,pos_lut,neg_lut);
pitch = width * img_bpp;
for (row = 0; row < 4; row ++)
{
src_rows[row] = new (unsigned char, pitch);
neg_rows[row] = new (long int, pitch);
}
dst_row = new (unsigned char, pitch);
/** Pre-load the first row for the filter... **/
memcpy(src_rows[0], src_region, pitch);
for (i = pitch, src_ptr = src_rows[0], neg_ptr = neg_rows[0];
i > 0; i --, src_ptr ++, neg_ptr ++)
*neg_ptr = neg_lut[*src_ptr];
row = 1;
count = 1;
/** Sharpen... **/
for (y = 0; y < height; y ++)
{
/** Load the next pixel row... **/
if ((y + 1) < height)
{
/** Check to see if our src_rows[] array is overflowing yet... **/
if (count >= 3)
count --;
/** Grab the next row... **/
memcpy(src_rows[row], (src_region + pitch*(y+1)), pitch);
for (i = pitch, src_ptr = src_rows[row], neg_ptr = neg_rows[row];
i > 0; i --, src_ptr ++, neg_ptr ++)
*neg_ptr = neg_lut[*src_ptr];
count ++;
row = (row + 1) & 3;
}
else
{
/** No more pixels at the bottom... Drop the oldest samples... **/
count --;
}
/** Now sharpen pixels and save the results... **/
if (count == 3)
{
rgb_filter(width, pos_lut, neg_lut,
src_rows[(row + 2) & 3], dst_row,
neg_rows[(row + 1) & 3] + img_bpp,
neg_rows[(row + 2) & 3] + img_bpp,
neg_rows[(row + 3) & 3] + img_bpp);
/** Set the row... **/
memcpy((dest_region + pitch*y), dst_row, pitch);
}
else if (count == 2)
{
if (y == 0) /* first row */
memcpy((dest_region), src_rows[0], pitch);
else /* last row */
memcpy((dest_region + pitch*(y)), src_rows[(height-1)&3], pitch);
}
} /* for */
/** OK, we're done. Free all memory used... **/
for (row = 0; row < 4; row ++)
{
free (src_rows[row]);
free (neg_rows[row]);
}
free (dst_row);
}
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