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gimp/app/core/gimp-transform-region.c

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/* GIMP - The GNU Image Manipulation Program
* Copyright (C) 1995-2003 Spencer Kimball, Peter Mattis, and others
*
* 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 <stdlib.h>
#include <glib-object.h>
#include "libgimpbase/gimpbase.h"
#include "libgimpmath/gimpmath.h"
#include "core-types.h"
#include "base/pixel-region.h"
#include "base/pixel-surround.h"
#include "base/tile-manager.h"
#include "base/tile.h"
#include "paint-funcs/scale-funcs.h"
#include "gimp-transform-region.h"
#include "gimpchannel.h"
#include "gimpcontext.h"
#include "gimpimage.h"
#include "gimppickable.h"
#include "gimpprogress.h"
/* forward function prototypes */
static gboolean supersample_dtest (gdouble u0, gdouble v0,
gdouble u1, gdouble v1,
gdouble u2, gdouble v2,
gdouble u3, gdouble v3);
static void sample_adapt (TileManager *tm,
gdouble uc, gdouble vc,
gdouble u0, gdouble v0,
gdouble u1, gdouble v1,
gdouble u2, gdouble v2,
gdouble u3, gdouble v3,
gint level,
guchar *color,
guchar *bg_color,
gint bpp,
gint alpha);
static void sample_cubic (PixelSurround *surround,
gdouble u,
gdouble v,
guchar *color,
gint bytes,
gint alpha);
static void sample_linear (PixelSurround *surround,
gdouble u,
gdouble v,
guchar *color,
gint bytes,
gint alpha);
/* public functions */
void
gimp_transform_region (GimpPickable *pickable,
GimpContext *context,
TileManager *orig_tiles,
PixelRegion *destPR,
gint dest_x1,
gint dest_y1,
gint dest_x2,
gint dest_y2,
const GimpMatrix3 *matrix,
GimpInterpolationType interpolation_type,
gboolean supersample,
gint recursion_level,
GimpProgress *progress)
{
PixelSurround surround;
GimpImageType pickable_type;
GimpMatrix3 m;
gint x, y; /* target coordinates */
gint u1, v1, u2, v2; /* source bounding box */
gdouble uinc, vinc, winc; /* increments in source coordinates
* per horizontal target coordinate
*/
gdouble u[5], v[5]; /* source coordinates,
*
* 2 0 is sample in the center
* / \ of pixel
* 1 0 3 1..4 is offset 1 pixel in
* \ / each direction
* 4 (in target space)
*/
gdouble tu[5], tv[5], tw[5]; /* undivided source coordinates and
* divisor
*/
gint coords;
gint alpha;
gint width;
gint bytes;
guchar *dest, *d;
guchar bg_color[MAX_CHANNELS];
tile_manager_get_offsets (orig_tiles, &u1, &v1);
u2 = u1 + tile_manager_width (orig_tiles);
v2 = v1 + tile_manager_height (orig_tiles);
m = *matrix;
gimp_matrix3_invert (&m);
alpha = 0;
width = dest_x2 - dest_x1;
bytes = destPR->bytes;
/* turn interpolation off for simple transformations (e.g. rot90) */
if (gimp_matrix3_is_simple (matrix))
interpolation_type = GIMP_INTERPOLATION_NONE;
pickable_type = gimp_pickable_get_image_type (pickable);
/* Get the background color */
gimp_image_get_background (gimp_pickable_get_image (pickable), context,
pickable_type, bg_color);
switch (GIMP_IMAGE_TYPE_BASE_TYPE (pickable_type))
{
case GIMP_RGB:
bg_color[ALPHA_PIX] = TRANSPARENT_OPACITY;
alpha = ALPHA_PIX;
break;
case GIMP_GRAY:
bg_color[ALPHA_G_PIX] = TRANSPARENT_OPACITY;
alpha = ALPHA_G_PIX;
break;
case GIMP_INDEXED:
bg_color[ALPHA_I_PIX] = TRANSPARENT_OPACITY;
alpha = ALPHA_I_PIX;
/* If the image is indexed color, ignore interpolation value */
interpolation_type = GIMP_INTERPOLATION_NONE;
break;
default:
g_assert_not_reached ();
break;
}
/* "Outside" a channel is transparency, not the bg color */
if (GIMP_IS_CHANNEL (pickable))
bg_color[0] = TRANSPARENT_OPACITY;
/* setting alpha = 0 will cause the channel's value to be treated
* as alpha and the color channel loops never to be entered
*/
if (tile_manager_bpp (orig_tiles) == 1)
alpha = 0;
/* initialise the pixel_surround and pixel_cache accessors */
switch (interpolation_type)
{
case GIMP_INTERPOLATION_NONE:
break;
case GIMP_INTERPOLATION_CUBIC:
pixel_surround_init (&surround, orig_tiles, 4, 4, bg_color);
break;
case GIMP_INTERPOLATION_LINEAR:
pixel_surround_init (&surround, orig_tiles, 2, 2, bg_color);
break;
case GIMP_INTERPOLATION_LANCZOS:
break;
}
dest = g_new (guchar, width * bytes);
/* these loops could be rearranged, depending on which bit of code
* you'd most like to write more than once.
*/
if (interpolation_type == GIMP_INTERPOLATION_LANCZOS)
{
gfloat *lanczos; /* Lanczos lookup table */
gdouble x_kernel[LANCZOS_WIDTH2]; /* 1-D kernels of window coeffs */
gdouble y_kernel[LANCZOS_WIDTH2];
gdouble x_sum, y_sum; /* sum of Lanczos weights */
gdouble uw;
gdouble ww;
gdouble vw;
gdouble du;
gdouble dv;
gint pos;
gdouble newval;
gdouble arecip;
gdouble aval;
guchar lwin[LANCZOS_WIDTH2 * LANCZOS_WIDTH2][MAX_CHANNELS + 1];
gint b, u, v, i, j;
gint pu, pv, su, sv;
/* allocate and fill lanczos lookup table */
lanczos = create_lanczos_lookup ();
for (y = dest_y1; y < dest_y2; y++)
{
if (progress && !(y & 0xf))
gimp_progress_set_value (progress,
(gdouble) (y - dest_y1) /
(gdouble) (dest_y2 - dest_y1));
pixel_region_get_row (destPR, 0, (y - dest_y1), width, dest, 1);
d = dest;
for (x = dest_x1; x < dest_x2; x++)
{
du = uw = m.coeff[0][0] * x + m.coeff[0][1] * y + m.coeff[0][2];
dv = vw = m.coeff[1][0] * x + m.coeff[1][1] * y + m.coeff[1][2];
ww = m.coeff[2][0] * x + m.coeff[2][1] * y + m.coeff[2][2];
if (ww == 1.0)
{
du = uw;
dv = vw;
}
else if (ww != 0.0)
{
du = uw / ww;
dv = vw / ww;
}
else
{
g_warning ("homogeneous coordinate = 0...\n");
}
u = (gint) du;
v = (gint) dv;
/* get weight for fractional error */
su = (gint) ((du - u) * LANCZOS_SPP);
sv = (gint) ((dv - v) * LANCZOS_SPP);
if (u < u1 || v < v1 ||
u >= u2 || v >= v2)
{
/* not in source range */
/* increment the destination pointers */
for (b = 0; b < bytes; b++)
*d++ = bg_color[b];
}
else
{
pos = 0;
for (j = 0; j < LANCZOS_WIDTH2 ; j++)
for (i = 0; i < LANCZOS_WIDTH2 ; i++, pos++)
{
pu = CLAMP (u + i - LANCZOS_WIDTH, u1, u2 - 1);
pv = CLAMP (v + j - LANCZOS_WIDTH, v1, v2 - 1);
read_pixel_data_1 (orig_tiles, pu - u1, pv - v1,
&lwin[pos][0]);
}
/* fill 1D kernels */
for (x_sum = y_sum = 0.0, i = LANCZOS_WIDTH; i >= -LANCZOS_WIDTH; i--)
{
pos = i * LANCZOS_SPP;
x_sum += x_kernel[LANCZOS_WIDTH + i] = lanczos[ABS (su - pos)];
y_sum += y_kernel[LANCZOS_WIDTH + i] = lanczos[ABS (sv - pos)];
}
/* normalise the weighted arrays */
for (i = 0; i < LANCZOS_WIDTH2 ; i++)
{
x_kernel[i] /= x_sum;
y_kernel[i] /= y_sum;
}
pos = 0;
aval = 0.0;
for (j = 0; j < LANCZOS_WIDTH2 ; j++)
for (i = 0; i < LANCZOS_WIDTH2 ; i++, pos++)
{
aval += y_kernel[j] * x_kernel[i] * lwin[pos][alpha];
}
if (aval <= 0.0)
{
arecip = 0.0;
aval = 0;
}
else if (aval > 255.0)
{
arecip = 1.0 / aval;
aval = 255;
}
else
{
arecip = 1.0 / aval;
}
for (b = 0; b < alpha; b++)
{
pos = 0;
newval = 0.0;
for (j = 0; j < LANCZOS_WIDTH2 ; j++)
for (i = 0; i < LANCZOS_WIDTH2 ; i++, pos++)
{
newval += y_kernel[j] * x_kernel[i] * lwin[pos][b] * lwin[pos][alpha];
}
newval *= arecip;
*d++ = CLAMP (newval, 0, 255);
}
*d++ = RINT (aval);
}
}
/* set the pixel region row */
pixel_region_set_row (destPR, 0, (y - dest_y1), width, dest);
}
g_free (lanczos);
goto done;
}
uinc = m.coeff[0][0];
vinc = m.coeff[1][0];
winc = m.coeff[2][0];
coords = (interpolation_type != GIMP_INTERPOLATION_NONE) ? 5 : 1;
for (y = dest_y1; y < dest_y2; y++)
{
if (progress && !(y & 0xf))
gimp_progress_set_value (progress,
(gdouble) (y - dest_y1) /
(gdouble) (dest_y2 - dest_y1));
/* set up inverse transform steps */
tu[0] = uinc * dest_x1 + m.coeff[0][1] * y + m.coeff[0][2];
tv[0] = vinc * dest_x1 + m.coeff[1][1] * y + m.coeff[1][2];
tw[0] = winc * dest_x1 + m.coeff[2][1] * y + m.coeff[2][2];
if (interpolation_type != GIMP_INTERPOLATION_NONE)
{
gdouble xx = dest_x1;
gdouble yy = y;
tu[1] = uinc * (xx - 1) + m.coeff[0][1] * (yy ) + m.coeff[0][2];
tv[1] = vinc * (xx - 1) + m.coeff[1][1] * (yy ) + m.coeff[1][2];
tw[1] = winc * (xx - 1) + m.coeff[2][1] * (yy ) + m.coeff[2][2];
tu[2] = uinc * (xx ) + m.coeff[0][1] * (yy - 1) + m.coeff[0][2];
tv[2] = vinc * (xx ) + m.coeff[1][1] * (yy - 1) + m.coeff[1][2];
tw[2] = winc * (xx ) + m.coeff[2][1] * (yy - 1) + m.coeff[2][2];
tu[3] = uinc * (xx + 1) + m.coeff[0][1] * (yy ) + m.coeff[0][2];
tv[3] = vinc * (xx + 1) + m.coeff[1][1] * (yy ) + m.coeff[1][2];
tw[3] = winc * (xx + 1) + m.coeff[2][1] * (yy ) + m.coeff[2][2];
tu[4] = uinc * (xx ) + m.coeff[0][1] * (yy + 1) + m.coeff[0][2];
tv[4] = vinc * (xx ) + m.coeff[1][1] * (yy + 1) + m.coeff[1][2];
tw[4] = winc * (xx ) + m.coeff[2][1] * (yy + 1) + m.coeff[2][2];
}
d = dest;
for (x = dest_x1; x < dest_x2; x++)
{
gint i; /* normalize homogeneous coords */
for (i = 0; i < coords; i++)
{
if (tw[i] == 1.0)
{
u[i] = tu[i];
v[i] = tv[i];
}
else if (tw[i] != 0.0)
{
u[i] = tu[i] / tw[i];
v[i] = tv[i] / tw[i];
}
else
{
g_warning ("homogeneous coordinate = 0...\n");
}
}
/* Set the destination pixels */
if (interpolation_type == GIMP_INTERPOLATION_NONE)
{
guchar color[MAX_CHANNELS];
gint iu = (gint) u[0];
gint iv = (gint) v[0];
gint b;
if (iu >= u1 && iu < u2 &&
iv >= v1 && iv < v2)
{
/* u, v coordinates into source tiles */
gint u = iu - u1;
gint v = iv - v1;
read_pixel_data_1 (orig_tiles, u, v, color);
for (b = 0; b < bytes; b++)
*d++ = color[b];
}
else /* not in source range */
{
/* increment the destination pointers */
for (b = 0; b < bytes; b++)
*d++ = bg_color[b];
}
}
else
{
gint b;
if (u [0] < u1 || v [0] < v1 ||
u [0] >= u2 || v [0] >= v2 )
{
/* not in source range */
/* increment the destination pointers */
for (b = 0; b < bytes; b++)
*d++ = bg_color[b];
}
else
{
guchar color[MAX_CHANNELS];
/* clamp texture coordinates */
for (b = 0; b < 5; b++)
{
u[b] = CLAMP (u[b], u1, u2 - 1);
v[b] = CLAMP (v[b], v1, v2 - 1);
}
if (supersample &&
supersample_dtest (u[1], v[1], u[2], v[2],
u[3], v[3], u[4], v[4]))
{
sample_adapt (orig_tiles,
u[0]-u1, v[0]-v1,
u[1]-u1, v[1]-v1,
u[2]-u1, v[2]-v1,
u[3]-u1, v[3]-v1,
u[4]-u1, v[4]-v1,
recursion_level,
color, bg_color, bytes, alpha);
}
else
{
switch (interpolation_type)
{
case GIMP_INTERPOLATION_NONE:
break;
case GIMP_INTERPOLATION_LINEAR:
sample_linear (&surround, u[0] - u1, v[0] - v1,
color, bytes, alpha);
break;
case GIMP_INTERPOLATION_CUBIC:
sample_cubic (&surround, u[0] - u1, v[0] - v1,
color, bytes, alpha);
break;
case GIMP_INTERPOLATION_LANCZOS:
break;
}
}
/* Set the destination pixel */
for (b = 0; b < bytes; b++)
*d++ = color[b];
}
}
for (i = 0; i < coords; i++)
{
tu[i] += uinc;
tv[i] += vinc;
tw[i] += winc;
}
}
/* set the pixel region row */
pixel_region_set_row (destPR, 0, (y - dest_y1), width, dest);
}
done:
if (progress)
gimp_progress_set_value (progress, 1.0);
switch (interpolation_type)
{
case GIMP_INTERPOLATION_NONE:
break;
case GIMP_INTERPOLATION_CUBIC:
case GIMP_INTERPOLATION_LINEAR:
pixel_surround_clear (&surround);
break;
case GIMP_INTERPOLATION_LANCZOS:
break;
}
g_free (dest);
}
/* private functions */
#define BILINEAR(jk, j1k, jk1, j1k1, dx, dy) \
((1 - dy) * (jk + dx * (j1k - jk)) + \
dy * (jk1 + dx * (j1k1 - jk1)))
/* u & v are the subpixel coordinates of the point in
* the original selection's floating buffer.
* We need the two pixel coords around them:
* iu to iu + 1, iv to iv + 1
*/
static void
sample_linear (PixelSurround *surround,
gdouble u,
gdouble v,
guchar *color,
gint bytes,
gint alpha)
{
gdouble a_val, a_recip;
gint i;
gint iu = floor (u);
gint iv = floor (v);
gint row;
gdouble du,dv;
guchar *alphachan;
guchar *data;
/* lock the pixel surround */
data = pixel_surround_lock (surround, iu, iv);
row = pixel_surround_rowstride (surround);
/* the fractional error */
du = u - iu;
dv = v - iv;
/* calculate alpha value of result pixel */
alphachan = &data[alpha];
a_val = BILINEAR (alphachan[0], alphachan[bytes],
alphachan[row], alphachan[row + bytes], du, dv);
if (a_val <= 0.0)
{
a_recip = 0.0;
color[alpha] = 0.0;
}
else if (a_val >= 255.0)
{
a_recip = 1.0 / a_val;
color[alpha] = 255;
}
else
{
a_recip = 1.0 / a_val;
color[alpha] = RINT (a_val);
}
/* for colour channels c,
* result = bilinear (c * alpha) / bilinear (alpha)
*
* never entered for alpha == 0
*/
for (i = 0; i < alpha; i++)
{
gint newval = (a_recip *
BILINEAR (alphachan[0] * data[i],
alphachan[bytes] * data[bytes + i],
alphachan[row] * data[row + i],
alphachan[row + bytes] * data[row + bytes + i],
du, dv));
color[i] = CLAMP (newval, 0, 255);
}
pixel_surround_release (surround);
}
/* macros to handle conversion to/from fixed point, this fixed point code
* uses signed integers, by using 8 bits for the fractional part we have
*
* 1 bit sign
* 21 bits integer part
* 8 bit fractional part
*
* 1023 discrete subpixel sample positions should be enough for the needs
* of the supersampling algorithm, drawables where the dimensions have a need
* exceeding 2^21 ( 2097152px, will typically use terabytes of memory, when
* that is the common need, we can probably assume 64 bit integers and adjust
* FIXED_SHIFT accordingly.
*/
#define FIXED_SHIFT 10
#define FIXED_UNIT (1 << FIXED_SHIFT)
#define DOUBLE2FIXED(val) ((val) * FIXED_UNIT)
#define FIXED2DOUBLE(val) ((val) / FIXED_UNIT)
/*
bilinear interpolation of a fixed point pixel
*/
static void
sample_bi (TileManager *tm,
gint x,
gint y,
guchar *color,
guchar *bg_color,
gint bpp,
gint alpha)
{
guchar C[4][4];
gint i;
gint xscale = (x & (FIXED_UNIT-1));
gint yscale = (y & (FIXED_UNIT-1));
gint x0 = x >> FIXED_SHIFT;
gint y0 = y >> FIXED_SHIFT;
gint x1 = x0 + 1;
gint y1 = y0 + 1;
/* fill the color with default values, since read_pixel_data_1
* does nothing, when accesses are out of bounds.
*/
for (i = 0; i < 4; i++)
*(guint*) (&C[i]) = *(guint*) (bg_color);
read_pixel_data_1 (tm, x0, y0, C[0]);
read_pixel_data_1 (tm, x1, y0, C[2]);
read_pixel_data_1 (tm, x0, y1, C[1]);
read_pixel_data_1 (tm, x1, y1, C[3]);
#define lerp(v1,v2,r) \
(((guint)(v1) * (FIXED_UNIT - (guint)(r)) + \
(guint)(v2) * (guint)(r)) >> FIXED_SHIFT)
color[alpha]= lerp (lerp (C[0][alpha], C[1][alpha], yscale),
lerp (C[2][alpha], C[3][alpha], yscale), xscale);
if (color[alpha])
{ /* to avoid problems, calculate with premultiplied alpha */
for (i=0; i<alpha; i++)
{
C[0][i] = (C[0][i] * C[0][alpha] / 255);
C[1][i] = (C[1][i] * C[1][alpha] / 255);
C[2][i] = (C[2][i] * C[2][alpha] / 255);
C[3][i] = (C[3][i] * C[3][alpha] / 255);
}
for (i = 0; i < alpha; i++)
color[i] = lerp (lerp (C[0][i], C[1][i], yscale),
lerp (C[2][i], C[3][i], yscale), xscale);
}
else
{
for (i = 0; i < alpha; i++)
color[i] = 0;
}
#undef lerp
}
/*
* Returns TRUE if one of the deltas of the
* quad edge is > 1.0 (16.16 fixed values).
*/
static gboolean
supersample_test (gint x0, gint y0,
gint x1, gint y1,
gint x2, gint y2,
gint x3, gint y3)
{
if (abs (x0 - x1) > FIXED_UNIT ||
abs (x1 - x2) > FIXED_UNIT ||
abs (x2 - x3) > FIXED_UNIT ||
abs (x3 - x0) > FIXED_UNIT ||
abs (y0 - y1) > FIXED_UNIT ||
abs (y1 - y2) > FIXED_UNIT ||
abs (y2 - y3) > FIXED_UNIT ||
abs (y3 - y0) > FIXED_UNIT) return TRUE;
return FALSE;
}
/*
* Returns TRUE if one of the deltas of the
* quad edge is > 1.0 (double values).
*/
static gboolean
supersample_dtest (gdouble x0, gdouble y0,
gdouble x1, gdouble y1,
gdouble x2, gdouble y2,
gdouble x3, gdouble y3)
{
if (fabs (x0 - x1) > 1.0 ||
fabs (x1 - x2) > 1.0 ||
fabs (x2 - x3) > 1.0 ||
fabs (x3 - x0) > 1.0 ||
fabs (y0 - y1) > 1.0 ||
fabs (y1 - y2) > 1.0 ||
fabs (y2 - y3) > 1.0 ||
fabs (y3 - y0) > 1.0)
return TRUE;
return FALSE;
}
/*
sample a grid that is spaced according to the quadraliteral's edges,
it subdivides a maximum of level times before sampling.
0..3 is a cycle around the quad
*/
static void
get_sample (TileManager *tm,
gint xc, gint yc,
gint x0, gint y0,
gint x1, gint y1,
gint x2, gint y2,
gint x3, gint y3,
gint *cc,
gint level,
guint *color,
guchar *bg_color,
gint bpp,
gint alpha)
{
if (!level || !supersample_test (x0, y0, x1, y1, x2, y2, x3, y3))
{
gint i;
guchar C[4];
sample_bi (tm, xc, yc, C, bg_color, bpp, alpha);
for (i = 0; i < bpp; i++)
color[i]+= C[i];
(*cc)++; /* increase number of samples taken */
}
else
{
gint tx, lx, rx, bx, tlx, trx, blx, brx;
gint ty, ly, ry, by, tly, try, bly, bry;
/* calculate subdivided corner coordinates (including centercoords
thus using a bilinear interpolation,. almost as good as
doing the perspective transform for each subpixel coordinate*/
tx = (x0 + x1) / 2;
tlx = (x0 + xc) / 2;
trx = (x1 + xc) / 2;
lx = (x0 + x3) / 2;
rx = (x1 + x2) / 2;
blx = (x3 + xc) / 2;
brx = (x2 + xc) / 2;
bx = (x3 + x2) / 2;
ty = (y0 + y1) / 2;
tly = (y0 + yc) / 2;
try = (y1 + yc) / 2;
ly = (y0 + y3) / 2;
ry = (y1 + y2) / 2;
bly = (y3 + yc) / 2;
bry = (y2 + yc) / 2;
by = (y3 + y2) / 2;
get_sample (tm,
tlx,tly,
x0,y0, tx,ty, xc,yc, lx,ly,
cc, level-1, color, bg_color, bpp, alpha);
get_sample (tm,
trx,try,
tx,ty, x1,y1, rx,ry, xc,yc,
cc, level-1, color, bg_color, bpp, alpha);
get_sample (tm,
brx,bry,
xc,yc, rx,ry, x2,y2, bx,by,
cc, level-1, color, bg_color, bpp, alpha);
get_sample (tm,
blx,bly,
lx,ly, xc,yc, bx,by, x3,y3,
cc, level-1, color, bg_color, bpp, alpha);
}
}
static void
sample_adapt (TileManager *tm,
gdouble xc, gdouble yc,
gdouble x0, gdouble y0,
gdouble x1, gdouble y1,
gdouble x2, gdouble y2,
gdouble x3, gdouble y3,
gint level,
guchar *color,
guchar *bg_color,
gint bpp,
gint alpha)
{
gint cc = 0;
gint i;
guint C[MAX_CHANNELS];
C[0] = C[1] = C[2] = C[3] = 0;
get_sample (tm,
DOUBLE2FIXED (xc), DOUBLE2FIXED (yc),
DOUBLE2FIXED (x0), DOUBLE2FIXED (y0),
DOUBLE2FIXED (x1), DOUBLE2FIXED (y1),
DOUBLE2FIXED (x2), DOUBLE2FIXED (y2),
DOUBLE2FIXED (x3), DOUBLE2FIXED (y3),
&cc, level, C, bg_color, bpp, alpha);
if (!cc)
cc=1;
color[alpha] = C[alpha] / cc;
if (color[alpha])
{
/* go from premultiplied to postmultiplied alpha */
for (i = 0; i < alpha; i++)
color[i] = ((C[i] / cc) * 255) / color[alpha];
}
else
{
for (i = 0; i < alpha; i++)
color[i] = 0;
}
}
/* access interleaved pixels */
#define CUBIC_ROW(dx, row, step) \
gimp_drawable_transform_cubic(dx,\
(row)[0], (row)[step], (row)[step+step], (row)[step+step+step])
#define CUBIC_SCALED_ROW(dx, row, arow, step) \
gimp_drawable_transform_cubic(dx, \
(arow)[0] * (row)[0], \
(arow)[step] * (row)[step], \
(arow)[step+step] * (row)[step+step], \
(arow)[step+step+step] * (row)[step+step+step])
/* Note: cubic function no longer clips result. */
/* Inlining this function makes sample_cubic() run about 10% faster. (Sven) */
static inline gdouble
gimp_drawable_transform_cubic (gdouble dx,
gint jm1,
gint j,
gint jp1,
gint jp2)
{
gdouble result;
#if 0
/* Equivalent to Gimp 1.1.1 and earlier - some ringing */
result = ((( ( - jm1 + j - jp1 + jp2 ) * dx +
( jm1 + jm1 - j - j + jp1 - jp2 ) ) * dx +
( - jm1 + jp1 ) ) * dx + j );
/* Recommended by Mitchell and Netravali - too blurred? */
result = ((( ( - 7 * jm1 + 21 * j - 21 * jp1 + 7 * jp2 ) * dx +
( 15 * jm1 - 36 * j + 27 * jp1 - 6 * jp2 ) ) * dx +
( - 9 * jm1 + 9 * jp1 ) ) * dx + (jm1 + 16 * j + jp1) ) / 18.0;
#endif
/* Catmull-Rom - not bad */
result = ((( ( - jm1 + 3 * j - 3 * jp1 + jp2 ) * dx +
( 2 * jm1 - 5 * j + 4 * jp1 - jp2 ) ) * dx +
( - jm1 + jp1 ) ) * dx + (j + j) ) / 2.0;
return result;
}
/* u & v are the subpixel coordinates of the point in
* the original selection's floating buffer.
* We need the four integer pixel coords around them:
* iu to iu + 3, iv to iv + 3
*/
static void
sample_cubic (PixelSurround *surround,
gdouble u,
gdouble v,
guchar *color,
gint bytes,
gint alpha)
{
gdouble a_val, a_recip;
gint i;
gint iu = floor(u);
gint iv = floor(v);
gint row;
gdouble du,dv;
guchar *data;
/* lock the pixel surround */
data = pixel_surround_lock (surround, iu - 1 , iv - 1 );
row = pixel_surround_rowstride (surround);
/* the fractional error */
du = u - iu;
dv = v - iv;
/* calculate alpha of result */
a_val = gimp_drawable_transform_cubic
(dv,
CUBIC_ROW (du, data + alpha + row * 0, bytes),
CUBIC_ROW (du, data + alpha + row * 1, bytes),
CUBIC_ROW (du, data + alpha + row * 2, bytes),
CUBIC_ROW (du, data + alpha + row * 3, bytes));
if (a_val <= 0.0)
{
a_recip = 0.0;
color[alpha] = 0;
}
else if (a_val > 255.0)
{
a_recip = 1.0 / a_val;
color[alpha] = 255;
}
else
{
a_recip = 1.0 / a_val;
color[alpha] = RINT (a_val);
}
/* for colour channels c,
* result = bicubic (c * alpha) / bicubic (alpha)
*
* never entered for alpha == 0
*/
for (i = 0; i < alpha; i++)
{
gint newval = (a_recip *
gimp_drawable_transform_cubic
(dv,
CUBIC_SCALED_ROW (du,
i + data + row * 0,
data + alpha + row * 0,
bytes),
CUBIC_SCALED_ROW (du,
i + data + row * 1,
data + alpha + row * 1,
bytes),
CUBIC_SCALED_ROW (du,
i + data + row * 2,
data + alpha + row * 2,
bytes),
CUBIC_SCALED_ROW (du,
i + data + row * 3,
data + alpha + row * 3,
bytes)));
color[i] = CLAMP (newval, 0, 255);
}
pixel_surround_release (surround);
}
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