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app: add gimp_transform_polygon_coords()

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... which is the same as gimp_transform_polygon(), but using
GimpCoords for the vertices, instead of GimpVector2.

Specify when the input and output arguments may alias, in the
description of gimp_transform_polygon().
This commit is contained in:
Ell
2018-02-03 04:54:03 -05:00
parent ea34bbc92b
commit 6b62cce03b
2 changed files with 101 additions and 1 deletions
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96
app/core/gimp-transform-utils.c
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@ -24,6 +24,7 @@
#include "core-types.h"
#include "gimp-transform-utils.h"
#include "gimpcoords.h"
#define EPSILON 1e-6
@ -561,7 +562,11 @@ gimp_transform_polygon_is_convex (gdouble x1,
* which happens when the entire input is clipped. in general, the maximal
* possible number of transformed vertices is '3 * n_vertices / 2' (rounded
* down), however, for convex polygons the number is 'n_vertices + 1', and for
* a single line segment the number is 2.
* a single line segment ('n_vertices == 2' and 'closed == FALSE') the number
* is 2.
*
* 't_vertices' may not alias 'vertices', except when transforming a single
* line segment.
*/
void
gimp_transform_polygon (const GimpMatrix3 *matrix,
@ -638,3 +643,92 @@ gimp_transform_polygon (const GimpMatrix3 *matrix,
}
}
}
/* same as gimp_transform_polygon(), but using GimpCoords as the vertex type,
* instead of GimpVector2.
*/
void
gimp_transform_polygon_coords (const GimpMatrix3 *matrix,
const GimpCoords *vertices,
gint n_vertices,
gboolean closed,
GimpCoords *t_vertices,
gint *n_t_vertices)
{
GimpVector3 curr;
gboolean curr_visible;
gint i;
g_return_if_fail (matrix != NULL);
g_return_if_fail (vertices != NULL);
g_return_if_fail (n_vertices >= 0);
g_return_if_fail (t_vertices != NULL);
g_return_if_fail (n_t_vertices != NULL);
*n_t_vertices = 0;
if (n_vertices == 0)
return;
curr.x = matrix->coeff[0][0] * vertices[0].x +
matrix->coeff[0][1] * vertices[0].y +
matrix->coeff[0][2];
curr.y = matrix->coeff[1][0] * vertices[0].x +
matrix->coeff[1][1] * vertices[0].y +
matrix->coeff[1][2];
curr.z = matrix->coeff[2][0] * vertices[0].x +
matrix->coeff[2][1] * vertices[0].y +
matrix->coeff[2][2];
curr_visible = (curr.z >= GIMP_TRANSFORM_NEAR_Z);
for (i = 0; i < n_vertices; i++)
{
if (curr_visible)
{
t_vertices[*n_t_vertices] = vertices[i];
t_vertices[*n_t_vertices].x = curr.x / curr.z;
t_vertices[*n_t_vertices].y = curr.y / curr.z;
(*n_t_vertices)++;
}
if (i < n_vertices - 1 || closed)
{
GimpVector3 next;
gboolean next_visible;
gint j = (i + 1) % n_vertices;
next.x = matrix->coeff[0][0] * vertices[j].x +
matrix->coeff[0][1] * vertices[j].y +
matrix->coeff[0][2];
next.y = matrix->coeff[1][0] * vertices[j].x +
matrix->coeff[1][1] * vertices[j].y +
matrix->coeff[1][2];
next.z = matrix->coeff[2][0] * vertices[j].x +
matrix->coeff[2][1] * vertices[j].y +
matrix->coeff[2][2];
next_visible = (next.z >= GIMP_TRANSFORM_NEAR_Z);
if (next_visible != curr_visible)
{
gdouble ratio = (curr.z - GIMP_TRANSFORM_NEAR_Z) / (curr.z - next.z);
gimp_coords_mix (1.0 - ratio, &vertices[i],
ratio, &vertices[j],
&t_vertices[*n_t_vertices]);
t_vertices[*n_t_vertices].x = (curr.x + (next.x - curr.x) * ratio) /
GIMP_TRANSFORM_NEAR_Z;
t_vertices[*n_t_vertices].y = (curr.y + (next.y - curr.y) * ratio) /
GIMP_TRANSFORM_NEAR_Z;
(*n_t_vertices)++;
}
curr = next;
curr_visible = next_visible;
}
}
}