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mutter/src/gradient.c
Havoc Pennington d4b91dc654 now just uses meta_gradient_add_alpha (draw_op_as_pixbuf): implement alpha 
2002-05-31  Havoc Pennington  <hp@redhat.com>

	* src/theme.c (multiply_alpha): now just uses
	meta_gradient_add_alpha
	(draw_op_as_pixbuf): implement alpha gradients for tint, gradient,
	and image draw ops, so I can implement garrett's stuff.

	* src/gradient.c (meta_gradient_add_alpha): new function to
	multiply the alpha channel of a pixbuf by an alpha gradient
2002-05-31 21:18:11 +00:00

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/* Metacity gradient rendering */
/*
* Copyright (C) 2001 Havoc Pennington, 99% copied from wrlib in
* WindowMaker, Copyright (C) 1997-2000 Dan Pascu and Alfredo Kojima
*
* 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 "gradient.h"
#include "util.h"
#include <string.h>
/* This is all Alfredo's and Dan's usual very nice WindowMaker code,
* slightly GTK-ized
*/
static GdkPixbuf* meta_gradient_create_horizontal (int width,
int height,
const GdkColor *from,
const GdkColor *to);
static GdkPixbuf* meta_gradient_create_vertical (int width,
int height,
const GdkColor *from,
const GdkColor *to);
static GdkPixbuf* meta_gradient_create_diagonal (int width,
int height,
const GdkColor *from,
const GdkColor *to);
static GdkPixbuf* meta_gradient_create_multi_horizontal (int width,
int height,
const GdkColor *colors,
int count);
static GdkPixbuf* meta_gradient_create_multi_vertical (int width,
int height,
const GdkColor *colors,
int count);
static GdkPixbuf* meta_gradient_create_multi_diagonal (int width,
int height,
const GdkColor *colors,
int count);
/* Used as the destroy notification function for gdk_pixbuf_new() */
static void
free_buffer (guchar *pixels, gpointer data)
{
g_free (pixels);
}
static GdkPixbuf*
blank_pixbuf (int width, int height, gboolean no_padding)
{
guchar *buf;
int rowstride;
g_return_val_if_fail (width > 0, NULL);
g_return_val_if_fail (height > 0, NULL);
if (no_padding)
rowstride = width * 3;
else
/* Always align rows to 32-bit boundaries */
rowstride = 4 * ((3 * width + 3) / 4);
buf = g_try_malloc (height * rowstride);
if (!buf)
return NULL;
return gdk_pixbuf_new_from_data (buf, GDK_COLORSPACE_RGB,
FALSE, 8,
width, height, rowstride,
free_buffer, NULL);
}
GdkPixbuf*
meta_gradient_create_simple (int width,
int height,
const GdkColor *from,
const GdkColor *to,
MetaGradientType style)
{
switch (style)
{
case META_GRADIENT_HORIZONTAL:
return meta_gradient_create_horizontal (width, height,
from, to);
case META_GRADIENT_VERTICAL:
return meta_gradient_create_vertical (width, height,
from, to);
case META_GRADIENT_DIAGONAL:
return meta_gradient_create_diagonal (width, height,
from, to);
case META_GRADIENT_LAST:
break;
}
g_assert_not_reached ();
return NULL;
}
GdkPixbuf*
meta_gradient_create_multi (int width,
int height,
const GdkColor *colors,
int n_colors,
MetaGradientType style)
{
if (n_colors > 2)
{
switch (style)
{
case META_GRADIENT_HORIZONTAL:
return meta_gradient_create_multi_horizontal (width, height, colors, n_colors);
case META_GRADIENT_VERTICAL:
return meta_gradient_create_multi_vertical (width, height, colors, n_colors);
case META_GRADIENT_DIAGONAL:
return meta_gradient_create_multi_diagonal (width, height, colors, n_colors);
case META_GRADIENT_LAST:
g_assert_not_reached ();
break;
}
}
else if (n_colors > 1)
{
return meta_gradient_create_simple (width, height, &colors[0], &colors[1],
style);
}
else if (n_colors > 0)
{
return meta_gradient_create_simple (width, height, &colors[0], &colors[0],
style);
}
g_assert_not_reached ();
return NULL;
}
/* Interwoven essentially means we have two vertical gradients,
* cut into horizontal strips of the given thickness, and then the strips
* are alternated. I'm not sure what it's good for, just copied since
* WindowMaker had it.
*/
GdkPixbuf*
meta_gradient_create_interwoven (int width,
int height,
const GdkColor colors1[2],
int thickness1,
const GdkColor colors2[2],
int thickness2)
{
int i, j, k, l, ll;
long r1, g1, b1, dr1, dg1, db1;
long r2, g2, b2, dr2, dg2, db2;
GdkPixbuf *pixbuf;
unsigned char *ptr;
unsigned char rr, gg, bb;
unsigned char *pixels;
int rowstride;
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
r1 = colors1[0].red<<8;
g1 = colors1[0].green<<8;
b1 = colors1[0].blue<<8;
r2 = colors2[0].red<<8;
g2 = colors2[0].green<<8;
b2 = colors2[0].blue<<8;
dr1 = ((colors1[1].red-colors1[0].red)<<8)/(int)height;
dg1 = ((colors1[1].green-colors1[0].green)<<8)/(int)height;
db1 = ((colors1[1].blue-colors1[0].blue)<<8)/(int)height;
dr2 = ((colors2[1].red-colors2[0].red)<<8)/(int)height;
dg2 = ((colors2[1].green-colors2[0].green)<<8)/(int)height;
db2 = ((colors2[1].blue-colors2[0].blue)<<8)/(int)height;
for (i=0,k=0,l=0,ll=thickness1; i<height; i++)
{
ptr = pixels + i * rowstride;
if (k == 0)
{
rr = r1>>16;
gg = g1>>16;
bb = b1>>16;
}
else
{
rr = r2>>16;
gg = g2>>16;
bb = b2>>16;
}
for (j=0; j<width/8; j++)
{
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
}
switch (width%8)
{
case 7: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 6: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 5: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 4: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 3: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 2: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 1: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
}
if (++l == ll)
{
if (k == 0)
{
k = 1;
ll = thickness2;
}
else
{
k = 0;
ll = thickness1;
}
l = 0;
}
r1+=dr1;
g1+=dg1;
b1+=db1;
r2+=dr2;
g2+=dg2;
b2+=db2;
}
return pixbuf;
}
/*
*----------------------------------------------------------------------
* meta_gradient_create_horizontal--
* Renders a horizontal linear gradient of the specified size in the
* GdkPixbuf format with a border of the specified type.
*
* Returns:
* A 24bit GdkPixbuf with the gradient (no alpha channel).
*
* Side effects:
* None
*----------------------------------------------------------------------
*/
static GdkPixbuf*
meta_gradient_create_horizontal (int width, int height,
const GdkColor *from,
const GdkColor *to)
{
int i;
long r, g, b, dr, dg, db;
GdkPixbuf *pixbuf;
unsigned char *ptr;
unsigned char *pixels;
int r0, g0, b0;
int rf, gf, bf;
int rowstride;
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
ptr = pixels;
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
r0 = (guchar) (from->red / 256.0);
g0 = (guchar) (from->green / 256.0);
b0 = (guchar) (from->blue / 256.0);
rf = (guchar) (to->red / 256.0);
gf = (guchar) (to->green / 256.0);
bf = (guchar) (to->blue / 256.0);
r = r0 << 16;
g = g0 << 16;
b = b0 << 16;
dr = ((rf-r0)<<16)/(int)width;
dg = ((gf-g0)<<16)/(int)width;
db = ((bf-b0)<<16)/(int)width;
/* render the first line */
for (i=0; i<width; i++)
{
*(ptr++) = (unsigned char)(r>>16);
*(ptr++) = (unsigned char)(g>>16);
*(ptr++) = (unsigned char)(b>>16);
r += dr;
g += dg;
b += db;
}
/* copy the first line to the other lines */
for (i=1; i<height; i++)
{
memcpy (&(pixels[i*rowstride]), pixels, rowstride);
}
return pixbuf;
}
/*
*----------------------------------------------------------------------
* meta_gradient_create_vertical--
* Renders a vertical linear gradient of the specified size in the
* GdkPixbuf format with a border of the specified type.
*
* Returns:
* A 24bit GdkPixbuf with the gradient (no alpha channel).
*
* Side effects:
* None
*----------------------------------------------------------------------
*/
static GdkPixbuf*
meta_gradient_create_vertical (int width, int height,
const GdkColor *from,
const GdkColor *to)
{
int i, j;
long r, g, b, dr, dg, db;
GdkPixbuf *pixbuf;
unsigned char *ptr;
unsigned char rr, gg, bb;
int r0, g0, b0;
int rf, gf, bf;
int rowstride;
unsigned char *pixels;
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
r0 = (guchar) (from->red / 256.0);
g0 = (guchar) (from->green / 256.0);
b0 = (guchar) (from->blue / 256.0);
rf = (guchar) (to->red / 256.0);
gf = (guchar) (to->green / 256.0);
bf = (guchar) (to->blue / 256.0);
r = r0<<16;
g = g0<<16;
b = b0<<16;
dr = ((rf-r0)<<16)/(int)height;
dg = ((gf-g0)<<16)/(int)height;
db = ((bf-b0)<<16)/(int)height;
for (i=0; i<height; i++)
{
ptr = pixels + i * rowstride;
rr = r>>16;
gg = g>>16;
bb = b>>16;
for (j=0; j<width/8; j++)
{
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
*(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
}
switch (width%8)
{
case 7: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 6: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 5: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 4: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 3: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 2: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
case 1: *(ptr++) = rr; *(ptr++) = gg; *(ptr++) = bb;
}
r+=dr;
g+=dg;
b+=db;
}
return pixbuf;
}
/*
*----------------------------------------------------------------------
* meta_gradient_create_diagonal--
* Renders a diagonal linear gradient of the specified size in the
* GdkPixbuf format with a border of the specified type.
*
* Returns:
* A 24bit GdkPixbuf with the gradient (no alpha channel).
*
* Side effects:
* None
*----------------------------------------------------------------------
*/
static GdkPixbuf*
meta_gradient_create_diagonal (int width, int height,
const GdkColor *from,
const GdkColor *to)
{
GdkPixbuf *pixbuf, *tmp;
int j;
float a, offset;
unsigned char *ptr;
int r0, g0, b0;
int rf, gf, bf;
unsigned char *pixels;
int rowstride;
if (width == 1)
return meta_gradient_create_vertical (width, height, from, to);
else if (height == 1)
return meta_gradient_create_horizontal (width, height, from, to);
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
tmp = meta_gradient_create_horizontal (2*width-1, 1, from, to);
if (!tmp)
{
g_object_unref (G_OBJECT (pixbuf));
return NULL;
}
r0 = (guchar) (from->red / 256.0);
g0 = (guchar) (from->green / 256.0);
b0 = (guchar) (from->blue / 256.0);
rf = (guchar) (to->red / 256.0);
gf = (guchar) (to->green / 256.0);
bf = (guchar) (to->blue / 256.0);
ptr = gdk_pixbuf_get_pixels (tmp);
a = ((float)(width - 1))/((float)(height - 1));
width = width * 3;
/* copy the first line to the other lines with corresponding offset */
for (j=0, offset=0.0; j<rowstride*height; j += rowstride)
{
memcpy (&(pixels[j]), &ptr[3*(int)offset], width);
offset += a;
}
g_object_unref (G_OBJECT (tmp));
return pixbuf;
}
static GdkPixbuf*
meta_gradient_create_multi_horizontal (int width, int height,
const GdkColor *colors,
int count)
{
int i, j, k;
long r, g, b, dr, dg, db;
GdkPixbuf *pixbuf;
unsigned char *ptr;
unsigned char *pixels;
int width2;
int rowstride;
g_return_val_if_fail (count > 2, NULL);
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
ptr = pixels;
if (count > width)
count = width;
if (count > 1)
width2 = width/(count-1);
else
width2 = width;
k = 0;
r = colors[0].red << 8;
g = colors[0].green << 8;
b = colors[0].blue << 8;
/* render the first line */
for (i=1; i<count; i++)
{
dr = ((int)(colors[i].red - colors[i-1].red) <<8)/(int)width2;
dg = ((int)(colors[i].green - colors[i-1].green)<<8)/(int)width2;
db = ((int)(colors[i].blue - colors[i-1].blue) <<8)/(int)width2;
for (j=0; j<width2; j++)
{
*ptr++ = (unsigned char)(r>>16);
*ptr++ = (unsigned char)(g>>16);
*ptr++ = (unsigned char)(b>>16);
r += dr;
g += dg;
b += db;
k++;
}
r = colors[i].red << 8;
g = colors[i].green << 8;
b = colors[i].blue << 8;
}
for (j=k; j<width; j++)
{
*ptr++ = (unsigned char)(r>>16);
*ptr++ = (unsigned char)(g>>16);
*ptr++ = (unsigned char)(b>>16);
}
/* copy the first line to the other lines */
for (i=1; i<height; i++)
{
memcpy (&(pixels[i*rowstride]), pixels, rowstride);
}
return pixbuf;
}
static GdkPixbuf*
meta_gradient_create_multi_vertical (int width, int height,
const GdkColor *colors,
int count)
{
int i, j, k;
long r, g, b, dr, dg, db;
GdkPixbuf *pixbuf;
unsigned char *ptr, *tmp, *pixels;
int height2;
int x;
unsigned char rr, gg, bb;
int rowstride;
int pad;
g_return_val_if_fail (count > 2, NULL);
pixbuf = blank_pixbuf (width, height, FALSE);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
pad = rowstride - (width * 3);
ptr = pixels;
if (count > height)
count = height;
if (count > 1)
height2 = height/(count-1);
else
height2 = height;
k = 0;
r = colors[0].red << 8;
g = colors[0].green << 8;
b = colors[0].blue << 8;
for (i=1; i<count; i++)
{
dr = ((int)(colors[i].red - colors[i-1].red) <<8)/(int)height2;
dg = ((int)(colors[i].green - colors[i-1].green)<<8)/(int)height2;
db = ((int)(colors[i].blue - colors[i-1].blue) <<8)/(int)height2;
for (j=0; j<height2; j++)
{
rr = r>>16;
gg = g>>16;
bb = b>>16;
for (x=0; x<width/4; x++)
{
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
}
switch (width%4)
{
case 3: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
case 2: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
case 1: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
}
ptr += pad;
r += dr;
g += dg;
b += db;
k++;
}
r = colors[i].red << 8;
g = colors[i].green << 8;
b = colors[i].blue << 8;
}
rr = r>>16;
gg = g>>16;
bb = b>>16;
if (k<height)
{
tmp = ptr;
for (x=0; x<width/4; x++)
{
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
*ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
}
switch (width%4)
{
case 3: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
case 2: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
case 1: *ptr++ = rr; *ptr++ = gg; *ptr++ = bb;
default: break;
}
ptr += pad;
for (j=k+1; j<height; j++)
{
memcpy (ptr, tmp, rowstride);
ptr += rowstride;
}
}
return pixbuf;
}
static GdkPixbuf*
meta_gradient_create_multi_diagonal (int width, int height,
const GdkColor *colors,
int count)
{
GdkPixbuf *pixbuf, *tmp;
float a, offset;
int j;
unsigned char *ptr;
unsigned char *pixels;
int rowstride;
g_return_val_if_fail (count > 2, NULL);
if (width == 1)
return meta_gradient_create_multi_vertical (width, height, colors, count);
else if (height == 1)
return meta_gradient_create_multi_horizontal (width, height, colors, count);
pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8,
width, height);
if (pixbuf == NULL)
return NULL;
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
if (count > width)
count = width;
if (count > height)
count = height;
if (count > 2)
tmp = meta_gradient_create_multi_horizontal (2*width-1, 1, colors, count);
else
/* wrlib multiplies these colors by 256 before passing them in, but
* I think it's a bug in wrlib, so changed here. I could be wrong
* though, if we notice two-color multi diagonals not working.
*/
tmp = meta_gradient_create_horizontal (2*width-1, 1,
&colors[0], &colors[1]);
if (!tmp)
{
g_object_unref (G_OBJECT (pixbuf));
return NULL;
}
ptr = gdk_pixbuf_get_pixels (tmp);
a = ((float)(width - 1))/((float)(height - 1));
width = width * 3;
/* copy the first line to the other lines with corresponding offset */
for (j=0, offset=0; j<rowstride*height; j += rowstride)
{
memcpy (&(pixels[j]), &ptr[3*(int)offset], width);
offset += a;
}
g_object_unref (G_OBJECT (tmp));
return pixbuf;
}
static void
simple_multiply_alpha (GdkPixbuf *pixbuf,
guchar alpha)
{
guchar *pixels;
int rowstride;
int height;
int row;
g_return_if_fail (GDK_IS_PIXBUF (pixbuf));
if (alpha == 255)
return;
g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
height = gdk_pixbuf_get_height (pixbuf);
row = 0;
while (row < height)
{
guchar *p;
guchar *end;
p = pixels + row * rowstride;
end = p + rowstride;
while (p != end)
{
p += 3; /* skip RGB */
/* multiply the two alpha channels. not sure this is right.
* but some end cases are that if the pixbuf contains 255,
* then it should be modified to contain "alpha"; if the
* pixbuf contains 0, it should remain 0.
*/
/* ((*p / 255.0) * (alpha / 255.0)) * 255; */
*p = (guchar) (((int) *p * (int) alpha) / (int) 255);
++p; /* skip A */
}
++row;
}
}
static void
meta_gradient_add_alpha_horizontal (GdkPixbuf *pixbuf,
const unsigned char *alphas,
int n_alphas)
{
int i, j;
long a, da;
unsigned char *p;
unsigned char *pixels;
int width2;
int rowstride;
int width, height;
unsigned char *gradient;
unsigned char *gradient_p;
unsigned char *gradient_end;
g_return_if_fail (n_alphas > 0);
if (n_alphas == 1)
{
/* Optimize this */
simple_multiply_alpha (pixbuf, alphas[0]);
return;
}
width = gdk_pixbuf_get_width (pixbuf);
height = gdk_pixbuf_get_height (pixbuf);
gradient = g_new (unsigned char, width);
gradient_end = gradient + width;
if (n_alphas > width)
n_alphas = width;
if (n_alphas > 1)
width2 = width / (n_alphas - 1);
else
width2 = width;
a = alphas[0] << 8;
gradient_p = gradient;
/* render the gradient into an array */
for (i = 1; i < n_alphas; i++)
{
da = (((int)(alphas[i] - (int) alphas[i-1])) << 8) / (int) width2;
for (j = 0; j < width2; j++)
{
*gradient_p++ = (a >> 8);
a += da;
}
a = alphas[i] << 8;
}
/* get leftover pixels */
while (gradient_p != gradient_end)
{
*gradient_p++ = a >> 8;
}
/* Now for each line of the pixbuf, fill in with the gradient */
pixels = gdk_pixbuf_get_pixels (pixbuf);
rowstride = gdk_pixbuf_get_rowstride (pixbuf);
p = pixels;
i = 0;
while (i < height)
{
unsigned char *row_end = p + rowstride;
gradient_p = gradient;
p += 3;
while (gradient_p != gradient_end)
{
/* multiply the two alpha channels. not sure this is right.
* but some end cases are that if the pixbuf contains 255,
* then it should be modified to contain "alpha"; if the
* pixbuf contains 0, it should remain 0.
*/
/* ((*p / 255.0) * (alpha / 255.0)) * 255; */
*p = (guchar) (((int) *p * (int) *gradient_p) / (int) 255);
p += 4;
++gradient_p;
}
p = row_end;
++i;
}
g_free (gradient);
}
void
meta_gradient_add_alpha (GdkPixbuf *pixbuf,
const guchar *alphas,
int n_alphas,
MetaGradientType type)
{
g_return_if_fail (GDK_IS_PIXBUF (pixbuf));
g_return_if_fail (gdk_pixbuf_get_has_alpha (pixbuf));
g_return_if_fail (n_alphas > 0);
switch (type)
{
case META_GRADIENT_HORIZONTAL:
meta_gradient_add_alpha_horizontal (pixbuf, alphas, n_alphas);
break;
case META_GRADIENT_VERTICAL:
g_printerr ("metacity: vertical alpha channel gradient not implemented yet\n");
break;
case META_GRADIENT_DIAGONAL:
g_printerr ("metacity: diagonal alpha channel gradient not implemented yet\n");
break;
case META_GRADIENT_LAST:
g_assert_not_reached ();
break;
}
}
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