Commit b8240b0d authored by Mukund Sivaraman's avatar Mukund Sivaraman

color-to-alpha: Indent code according to our style

parent 3e523499
......@@ -41,7 +41,7 @@ gegl_chant_color (value, _("Color"), "black",
static void prepare (GeglOperation *operation)
{
gegl_operation_set_format (operation, "input",
gegl_operation_set_format (operation, "input",
babl_format ("RGBA float"));
gegl_operation_set_format (operation, "output",
babl_format ("RGBA float"));
......@@ -51,76 +51,76 @@ static void prepare (GeglOperation *operation)
* An excerpt from a discussion on #gimp that sheds some light on the ideas
* behind the algorithm that is being used here.
*
<clahey> so if a1 > c1, a2 > c2, and a3 > c2 and a1 - c1 > a2-c2, a3-c3,
then a1 = b1 * alpha + c1 * (1-alpha)
So, maximizing alpha without taking b1 above 1 gives
a1 = alpha + c1(1-alpha) and therefore alpha = (a1-c1) / (1-c1).
<sjburges> clahey: btw, the ordering of that a2, a3 in the white->alpha didn't
matter
<clahey> sjburges: You mean that it could be either a1, a2, a3 or
a1, a3, a2?
<sjburges> yeah
<sjburges> because neither one uses the other
<clahey> sjburges: That's exactly as it should be. They are both just
getting reduced to the same amount, limited by the the darkest
color.
<clahey> Then a2 = b2 * alpha + c2 * (1- alpha). Solving for b2 gives
b2 = (a1-c2)/alpha + c2.
<sjburges> yeah
<clahey> That gives us are formula for if the background is darker than the
foreground? Yep.
<clahey> Next if a1 < c1, a2 < c2, a3 < c3, and c1-a1 > c2-a2, c3-a3, and
by our desired result a1 = b1 * alpha + c1 * (1-alpha),
we maximize alpha without taking b1 negative gives
alpha = 1 - a1 / c1.
<clahey> And then again, b2 = (a2-c2) / alpha + c2 by the same formula.
(Actually, I think we can use that formula for all cases, though
it may possibly introduce rounding error.
<clahey> sjburges: I like the idea of using floats to avoid rounding error.
Good call.
*/
<clahey> so if a1 > c1, a2 > c2, and a3 > c2 and a1 - c1 > a2-c2, a3-c3,
then a1 = b1 * alpha + c1 * (1-alpha)
So, maximizing alpha without taking b1 above 1 gives
a1 = alpha + c1(1-alpha) and therefore alpha = (a1-c1) / (1-c1).
<sjburges> clahey: btw, the ordering of that a2, a3 in the white->alpha didn't
matter
<clahey> sjburges: You mean that it could be either a1, a2, a3 or
a1, a3, a2?
<sjburges> yeah
<sjburges> because neither one uses the other
<clahey> sjburges: That's exactly as it should be. They are both just
getting reduced to the same amount, limited by the the darkest
color.
<clahey> Then a2 = b2 * alpha + c2 * (1- alpha). Solving for b2 gives
b2 = (a1-c2)/alpha + c2.
<sjburges> yeah
<clahey> That gives us are formula for if the background is darker than the
foreground? Yep.
<clahey> Next if a1 < c1, a2 < c2, a3 < c3, and c1-a1 > c2-a2, c3-a3, and
by our desired result a1 = b1 * alpha + c1 * (1-alpha),
we maximize alpha without taking b1 negative gives
alpha = 1 - a1 / c1.
<clahey> And then again, b2 = (a2-c2) / alpha + c2 by the same formula.
(Actually, I think we can use that formula for all cases, though
it may possibly introduce rounding error.
<clahey> sjburges: I like the idea of using floats to avoid rounding error.
Good call.
*/
static void
color_to_alpha (gfloat *color,
gfloat *src,
gint offset)
{
gint i;
gfloat temp[4];
temp[3] = src[offset + 3];
src[offset+3] = temp[3];
for (i=0; i<3; i++)
if (color[i] < 0.0001)
temp[i] = src[offset+i];
else if (src[offset+i] > color[i])
temp[i] = (src[offset+i] - color[i]) / (1.0 - color[i]);
else if (src[offset+i] < color[i])
temp[i] = (color[i] - src[offset+i]) / color[i];
else
temp[i] = 0.0;
if (temp[0] > temp[1])
{
if (temp[0] > temp[2])
src[offset+3] = temp[0];
else
src[offset+3] = temp[2];
}
else if (temp[1] > temp[2])
src[offset+3] = temp[1];
else
src[offset+3] = temp[2];
if (src[offset+3] < 0.0001)
return;
for (i=0; i<3; i++)
src[offset+i] = (src[offset+i] - color[i]) / src[offset+3] + color[i];
src[offset+3] *=temp[3];
gint i;
gfloat temp[4];
temp[3] = src[offset + 3];
src[offset+3] = temp[3];
for (i=0; i<3; i++)
if (color[i] < 0.0001)
temp[i] = src[offset+i];
else if (src[offset+i] > color[i])
temp[i] = (src[offset+i] - color[i]) / (1.0 - color[i]);
else if (src[offset+i] < color[i])
temp[i] = (color[i] - src[offset+i]) / color[i];
else
temp[i] = 0.0;
if (temp[0] > temp[1])
{
if (temp[0] > temp[2])
src[offset+3] = temp[0];
else
src[offset+3] = temp[2];
}
else if (temp[1] > temp[2])
src[offset+3] = temp[1];
else
src[offset+3] = temp[2];
if (src[offset+3] < 0.0001)
return;
for (i=0; i<3; i++)
src[offset+i] = (src[offset+i] - color[i]) / src[offset+3] + color[i];
src[offset+3] *=temp[3];
}
......@@ -144,7 +144,7 @@ process (GeglOperation *operation,
gegl_color_get_rgba4f (o->value, color);
for (x = 0; x < result->width * result->height; x++)
color_to_alpha (color, src_buf, 4 * x);
color_to_alpha (color, src_buf, 4 * x);
gegl_buffer_set (output, result, format, src_buf, GEGL_AUTO_ROWSTRIDE);
......
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