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gimp/app/paint-funcs/subsample-region.c

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/* GIMP - The GNU Image Manipulation Program
* Copyright (C) 1995 Spencer Kimball and Peter Mattis
*
* 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.
*/
#include "config.h"
#include <string.h>
#include <glib-object.h>
#include "paint-funcs-types.h"
#include "base/pixel-region.h"
#include "subsample-region.h"
#define EPSILON (0.0001) /* arbitary small number for avoiding zero */
void
subsample_region (PixelRegion *srcPR,
PixelRegion *destPR,
gint subsample)
{
const gint width = destPR->w;
const gint height = destPR->h;
const gint orig_width = srcPR->w / subsample;
const gint orig_height = srcPR->h / subsample;
const gdouble x_ratio = (gdouble) orig_width / (gdouble) width;
const gdouble y_ratio = (gdouble) orig_height / (gdouble) height;
const gint bytes = destPR->bytes;
const gint destwidth = destPR->rowstride;
const gboolean has_alpha = pixel_region_has_alpha (srcPR);
guchar *src, *s;
guchar *dest, *d;
gdouble *row, *r;
gint src_row, src_col;
gdouble x_sum, y_sum;
gdouble x_last, y_last;
gdouble *x_frac, y_frac;
gdouble tot_frac;
gint i, j;
gint b;
gint frac;
gboolean advance_dest;
#if 0
g_printerr ("subsample_region: (%d x %d) -> (%d x %d)\n",
orig_width, orig_height, width, height);
#endif
/* the data pointers... */
src = g_new (guchar, orig_width * bytes);
dest = destPR->data;
/* allocate an array to help with the calculations */
row = g_new (gdouble, width * bytes);
x_frac = g_new (gdouble, width + orig_width);
/* initialize the pre-calculated pixel fraction array */
src_col = 0;
x_sum = (gdouble) src_col;
x_last = x_sum;
for (i = 0; i < width + orig_width; i++)
{
if (x_sum + x_ratio <= (src_col + 1 + EPSILON))
{
x_sum += x_ratio;
x_frac[i] = x_sum - x_last;
}
else
{
src_col ++;
x_frac[i] = src_col - x_last;
}
x_last += x_frac[i];
}
/* clear the "row" array */
memset (row, 0, sizeof (gdouble) * width * bytes);
/* counters... */
src_row = 0;
y_sum = (gdouble) src_row;
y_last = y_sum;
pixel_region_get_row (srcPR,
srcPR->x, srcPR->y + src_row * subsample,
orig_width * subsample,
src, subsample);
/* Scale the selected region */
for (i = 0; i < height; )
{
src_col = 0;
x_sum = (gdouble) src_col;
/* determine the fraction of the src pixel we are using for y */
if (y_sum + y_ratio <= (src_row + 1 + EPSILON))
{
y_sum += y_ratio;
y_frac = y_sum - y_last;
advance_dest = TRUE;
}
else
{
src_row ++;
y_frac = src_row - y_last;
advance_dest = FALSE;
}
y_last += y_frac;
s = src;
r = row;
frac = 0;
j = width;
while (j)
{
tot_frac = x_frac[frac++] * y_frac;
if (has_alpha)
{
/* premultiply */
gdouble local_frac = tot_frac * (gdouble) s[bytes - 1] / 255.0;
for (b = 0; b < (bytes - 1); b++)
r[b] += s[b] * local_frac;
r[bytes - 1] += local_frac;
}
else
{
for (b = 0; b < bytes; b++)
r[b] += s[b] * tot_frac;
}
/* increment the destination */
if (x_sum + x_ratio <= (src_col + 1 + EPSILON))
{
r += bytes;
x_sum += x_ratio;
j--;
}
/* increment the source */
else
{
s += bytes;
src_col++;
}
}
if (advance_dest)
{
tot_frac = 1.0 / (x_ratio * y_ratio);
/* copy "row" to "dest" */
d = dest;
r = row;
j = width;
while (j--)
{
if (has_alpha)
{
/* unpremultiply */
gdouble alpha = r[bytes - 1];
if (alpha > EPSILON)
{
for (b = 0; b < (bytes - 1); b++)
d[b] = (guchar) ((r[b] / alpha) + 0.5);
d[bytes - 1] = (guchar) ((alpha * tot_frac * 255.0) + 0.5);
}
else
{
for (b = 0; b < bytes; b++)
d[b] = 0;
}
}
else
{
for (b = 0; b < bytes; b++)
d[b] = (guchar) ((r[b] * tot_frac) + 0.5);
}
r += bytes;
d += bytes;
}
dest += destwidth;
/* clear the "row" array */
memset (row, 0, sizeof (gdouble) * destwidth);
i++;
}
else
{
pixel_region_get_row (srcPR,
srcPR->x,
srcPR->y + src_row * subsample,
orig_width * subsample,
src, subsample);
}
}
/* free up temporary arrays */
g_free (row);
g_free (x_frac);
g_free (src);
}
void
subsample_indexed_region (PixelRegion *srcPR,
PixelRegion *destPR,
const guchar *cmap,
gint subsample)
{
const gint width = destPR->w;
const gint height = destPR->h;
const gint orig_width = srcPR->w / subsample;
const gint orig_height = srcPR->h / subsample;
const gdouble x_ratio = (gdouble) orig_width / (gdouble) width;
const gdouble y_ratio = (gdouble) orig_height / (gdouble) height;
const gint bytes = destPR->bytes;
const gint destwidth = destPR->rowstride;
const gboolean has_alpha = pixel_region_has_alpha (srcPR);
guchar *src, *s;
guchar *dest, *d;
gdouble *row, *r;
gint src_row, src_col;
gdouble x_sum, y_sum;
gdouble x_last, y_last;
gdouble *x_frac, y_frac;
gdouble tot_frac;
gint i, j;
gint b;
gint frac;
gboolean advance_dest;
g_return_if_fail (cmap != NULL);
/* the data pointers... */
src = g_new (guchar, orig_width * bytes);
dest = destPR->data;
/* allocate an array to help with the calculations */
row = g_new0 (gdouble, width * bytes);
x_frac = g_new (gdouble, width + orig_width);
/* initialize the pre-calculated pixel fraction array */
src_col = 0;
x_sum = (gdouble) src_col;
x_last = x_sum;
for (i = 0; i < width + orig_width; i++)
{
if (x_sum + x_ratio <= (src_col + 1 + EPSILON))
{
x_sum += x_ratio;
x_frac[i] = x_sum - x_last;
}
else
{
src_col++;
x_frac[i] = src_col - x_last;
}
x_last += x_frac[i];
}
/* counters... */
src_row = 0;
y_sum = (gdouble) src_row;
y_last = y_sum;
pixel_region_get_row (srcPR,
srcPR->x,
srcPR->y + src_row * subsample,
orig_width * subsample,
src,
subsample);
/* Scale the selected region */
for (i = 0; i < height; )
{
src_col = 0;
x_sum = (gdouble) src_col;
/* determine the fraction of the src pixel we are using for y */
if (y_sum + y_ratio <= (src_row + 1 + EPSILON))
{
y_sum += y_ratio;
y_frac = y_sum - y_last;
advance_dest = TRUE;
}
else
{
src_row++;
y_frac = src_row - y_last;
advance_dest = FALSE;
}
y_last += y_frac;
s = src;
r = row;
frac = 0;
j = width;
while (j)
{
gint index = *s * 3;
tot_frac = x_frac[frac++] * y_frac;
/* transform the color to RGB */
if (has_alpha)
{
if (s[ALPHA_I] & 0x80)
{
r[RED] += cmap[index++] * tot_frac;
r[GREEN] += cmap[index++] * tot_frac;
r[BLUE] += cmap[index++] * tot_frac;
r[ALPHA] += tot_frac;
}
/* else the pixel contributes nothing and needs not to be added
*/
}
else
{
r[RED] += cmap[index++] * tot_frac;
r[GREEN] += cmap[index++] * tot_frac;
r[BLUE] += cmap[index++] * tot_frac;
}
/* increment the destination */
if (x_sum + x_ratio <= (src_col + 1 + EPSILON))
{
r += bytes;
x_sum += x_ratio;
j--;
}
/* increment the source */
else
{
s += srcPR->bytes;
src_col++;
}
}
if (advance_dest)
{
tot_frac = 1.0 / (x_ratio * y_ratio);
/* copy "row" to "dest" */
d = dest;
r = row;
j = width;
while (j--)
{
if (has_alpha)
{
/* unpremultiply */
gdouble alpha = r[bytes - 1];
if (alpha > EPSILON)
{
for (b = 0; b < (bytes - 1); b++)
d[b] = (guchar) ((r[b] / alpha) + 0.5);
d[bytes - 1] = (guchar) ((alpha * tot_frac * 255.0) + 0.5);
}
else
{
for (b = 0; b < bytes; b++)
d[b] = 0;
}
}
else
{
for (b = 0; b < bytes; b++)
d[b] = (guchar) ((r[b] * tot_frac) + 0.5);
}
r += bytes;
d += bytes;
}
dest += destwidth;
/* clear the "row" array */
memset (row, 0, sizeof (gdouble) * destwidth);
i++;
}
else
{
pixel_region_get_row (srcPR,
srcPR->x,
srcPR->y + src_row * subsample,
orig_width * subsample,
src,
subsample);
}
}
/* free up temporary arrays */
g_free (row);
g_free (x_frac);
g_free (src);
}
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