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Bill Skaggs <weskaggs@primate.ucdavis.edu> 

* app/core/gimpchannel-combine.c: improve anti-aliasing for
	elliptical selections, as described in bug #147836.
This commit is contained in:
William Skaggs 2004-07-18 19:31:29 +00:00
parent 55c03a25b5
commit f7cca5f2f2
2 changed files with 125 additions and 86 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2004-07-18 Bill Skaggs <weskaggs@primate.ucdavis.edu>
* app/core/gimpchannel-combine.c: improve anti-aliasing for
elliptical selections, as described in bug #147836.
2004-07-18 Sven Neumann <sven@gimp.org>
* app/composite/gimp-composite-mmx.h: don't start a comment with

206
app/core/gimpchannel-combine.c
View File

@ -191,26 +191,44 @@ gimp_channel_combine_rect (GimpChannel *mask,
gimp_drawable_update (GIMP_DRAWABLE (mask), x, y, w, h);
}
/**
* gimp_channel_combine_ellipse:
* @mask: the channel with which to combine the ellipse
* @op: whether to replace, add to, or subtract from the current contents
* @x: x coordinate of upper left corner of ellipse
* @y: y coordinate of upper left corner of ellipse
* @w: width of ellipse bounding box
* @h: height of ellipse bounding box
* @antialias: if %TRUE, antialias the ellipse
*
* Mainly used for elliptical selections. If @op is "replace" or
* "add", sets pixels within the ellipse to 255. If @op is
* "subtract", sets pixels within to zero. If antialiasing is
* turned on, a pixels that impinge on the edge of the ellipse
* are set to intermediate values, depending on how much they
* overlap.
**/
void
gimp_channel_combine_ellipse (GimpChannel *mask,
GimpChannelOps op,
gint x,
gint y,
gint w,
gint h,
gboolean antialias)
GimpChannelOps op,
gint x,
gint y,
gint w,
gint h,
gboolean antialias)
{
gint i, j;
gint x0, x1, x2;
gint val, last;
gfloat a, b;
gfloat a_sqr, b_sqr, aob_sqr;
gfloat w_sqr, h_sqr;
gfloat y_sqr;
gfloat t0, t1;
gfloat r;
gfloat xj, yi;
gfloat xdist, ydist;
gfloat cx, cy;
gfloat rad;
gfloat dist;
gfloat r;
g_return_if_fail (GIMP_IS_CHANNEL (mask));
@ -227,91 +245,107 @@ gimp_channel_combine_ellipse (GimpChannel *mask,
for (i = y; i < (y + h); i++)
{
if (i >= 0 && i < GIMP_ITEM (mask)->height)
{
/* Non-antialiased code */
if (!antialias)
{
y_sqr = (i + 0.5 - cy) * (i + 0.5 - cy);
rad = sqrt (a_sqr - a_sqr * y_sqr / (double) b_sqr);
x1 = ROUND (cx - rad);
x2 = ROUND (cx + rad);
{
/* Non-antialiased code */
if (!antialias)
{
y_sqr = (i + 0.5 - cy) * (i + 0.5 - cy);
rad = sqrt (a_sqr - a_sqr * y_sqr / (double) b_sqr);
x1 = ROUND (cx - rad);
x2 = ROUND (cx + rad);
switch (op)
{
case GIMP_CHANNEL_OP_ADD:
case GIMP_CHANNEL_OP_REPLACE:
gimp_channel_add_segment (mask, x1, i, (x2 - x1), 255);
break;
switch (op)
{
case GIMP_CHANNEL_OP_ADD:
case GIMP_CHANNEL_OP_REPLACE:
gimp_channel_add_segment (mask, x1, i, (x2 - x1), 255);
break;
case GIMP_CHANNEL_OP_SUBTRACT:
gimp_channel_sub_segment (mask, x1, i, (x2 - x1), 255);
break;
case GIMP_CHANNEL_OP_SUBTRACT:
gimp_channel_sub_segment (mask, x1, i, (x2 - x1), 255);
break;
default:
g_warning ("Only ADD, REPLACE, and SUBTRACT are valid for channel_combine!");
break;
}
}
/* antialiasing */
else
{
x0 = x;
last = 0;
h_sqr = (i + 0.5 - cy) * (i + 0.5 - cy);
for (j = x; j < (x + w); j++)
{
w_sqr = (j + 0.5 - cx) * (j + 0.5 - cx);
default:
g_warning ("Only ADD, REPLACE, and SUBTRACT are valid for channel_combine!");
break;
}
}
/* antialiasing */
else
{
/** algorithm changed 7-18-04, because the previous one did not
* work well for eccentric ellipses. The new algorithm
* measures the distance to the ellipse in the X and Y directions,
* and uses trigonometry to approximate the distance to the
* ellipse as the distance to the hypotenuse of a right triangle
* whose legs are the X and Y distances. (WES)
**/
x0 = x;
last = 0;
yi = ABS (i + 0.5 - cy);
if (h_sqr != 0)
{
t0 = w_sqr / h_sqr;
t1 = a_sqr / (t0 + aob_sqr);
r = sqrt (t1 + t0 * t1);
rad = sqrt (w_sqr + h_sqr);
dist = rad - r;
}
else
dist = -1.0;
for (j = x; j < (x + w); j++)
{
xj = ABS (j + 0.5 - cx);
if (dist < -0.5)
val = 255;
else if (dist < 0.5)
val = (int) (255 * (1 - (dist + 0.5)));
else
val = 0;
if (yi < b)
xdist = xj - a * sqrt (1 - yi * yi / b_sqr);
else
xdist = 100.; /* anything large will work */
if (last != val && last)
{
switch (op)
{
case GIMP_CHANNEL_OP_ADD:
case GIMP_CHANNEL_OP_REPLACE:
gimp_channel_add_segment (mask, x0, i, j - x0, last);
break;
if (xj < a)
ydist = yi - b * sqrt (1 - xj * xj / a_sqr);
else
ydist = 100.; /* anything large will work */
r = hypot (xdist, ydist);
if (r < 0.001)
dist = 0.;
else
dist = xdist * ydist / r; /* trig formula for dist to hypotenuse */
case GIMP_CHANNEL_OP_SUBTRACT:
gimp_channel_sub_segment (mask, x0, i, j - x0, last);
break;
if (xdist < 0.)
dist *= -1;
default:
g_warning ("Only ADD, REPLACE, and SUBTRACT are valid for channel_combine!");
break;
}
}
if (dist < -0.5)
val = 255;
else if (dist < 0.5)
val = (int) (255 * (1 - (dist + 0.5)));
else
val = 0;
if (last != val)
{
x0 = j;
last = val;
/* because we are symetric accross the y axis we can
skip ahead a bit if we are inside the ellipse*/
if (val == 255 && j < cx)
j = cx + (cx - j) - 1;
}
}
if (last != val && last)
{
switch (op)
{
case GIMP_CHANNEL_OP_ADD:
case GIMP_CHANNEL_OP_REPLACE:
gimp_channel_add_segment (mask, x0, i, j - x0, last);
break;
if (last)
{
case GIMP_CHANNEL_OP_SUBTRACT:
gimp_channel_sub_segment (mask, x0, i, j - x0, last);
break;
default:
g_warning ("Only ADD, REPLACE, and SUBTRACT are valid for channel_combine!");
break;
}
}
if (last != val)
{
x0 = j;
last = val;
/* because we are symetric accross the y axis we can
skip ahead a bit if we are inside the ellipse*/
if (val == 255 && j < cx)
j = cx + (cx - j) - 1;
}
}
if (last)
{
switch (op)
{
case GIMP_CHANNEL_OP_ADD:
@ -327,8 +361,8 @@ gimp_channel_combine_ellipse (GimpChannel *mask,
g_warning ("Only ADD, REPLACE, and SUBTRACT are valid for channel_combine!");
break;
}
}
}
}
}
}
}