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Connected discontiguous polygon corners

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This commit is contained in:
Andrew Murray 2022-01-21 11:55:59 +11:00
parent 48d32fe81f
commit b894c8c73d
3 changed files with 52 additions and 7 deletions
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Tests/images/imagedraw/discontiguous_corners_polygon.png Normal file
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12
Tests/test_imagedraw.py
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@ -1440,3 +1440,15 @@ def test_continuous_horizontal_edges_polygon():
assert_image_equal_tofile(
img, expected, "continuous horizontal edges polygon failed"
)
def test_discontiguous_corners_polygon():
img, draw = create_base_image_draw((84, 68))
draw.polygon(((1, 21), (34, 4), (71, 1), (38, 18)), BLACK)
draw.polygon(((71, 44), (38, 27), (1, 24)), BLACK)
draw.polygon(
((38, 66), (5, 49), (77, 49), (47, 66), (82, 63), (82, 47), (1, 47), (1, 63)),
BLACK,
)
expected = os.path.join(IMAGES_PATH, "discontiguous_corners_polygon.png")
assert_image_similar_tofile(img, expected, 1)

41
src/libImaging/Draw.c
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@ -450,7 +450,8 @@ polygon_generic(Imaging im, int n, Edge *e, int ink, int eofill, hline_handler h
int edge_count = 0;
int ymin = im->ysize - 1;
int ymax = 0;
int i;
int i, j, k;
float adjacent_line_x, adjacent_line_x_other_edge;
if (n <= 0) {
return 0;
@ -493,16 +494,48 @@ polygon_generic(Imaging im, int n, Edge *e, int ink, int eofill, hline_handler h
return -1;
}
for (; ymin <= ymax; ymin++) {
int j = 0;
j = 0;
for (i = 0; i < edge_count; i++) {
Edge *current = edge_table[i];
if (ymin >= current->ymin && ymin <= current->ymax) {
xx[j++] = (ymin - current->y0) * current->dx + current->x0;
}
/* Needed to draw consistent polygons */
if (ymin == current->ymax && ymin < ymax) {
// Needed to draw consistent polygons
xx[j] = xx[j - 1];
j++;
} else if (current->dx != 0 && roundf(xx[j-1]) == xx[j-1]) {
// Connect discontiguous corners
for (k = 0; k < i; k++) {
Edge *other_edge = edge_table[k];
if ((current->dx > 0 && other_edge->dx <= 0) ||
(current->dx < 0 && other_edge->dx >= 0)) {
continue;
}
// Check if the two edges join to make a corner
if (xx[j-1] == (ymin - other_edge->y0) * other_edge->dx + other_edge->x0) {
// Determine points from the edges on the next row
// Or if this is the last row, check the previous row
int offset = ymin == ymax ? -1 : 1;
adjacent_line_x = (ymin + offset - current->y0) * current->dx + current->x0;
adjacent_line_x_other_edge = (ymin + offset - other_edge->y0) * other_edge->dx + other_edge->x0;
if (ymin == current->ymax) {
if (current->dx > 0) {
xx[k] = fmax(adjacent_line_x, adjacent_line_x_other_edge) + 1;
} else {
xx[k] = fmin(adjacent_line_x, adjacent_line_x_other_edge) - 1;
}
} else {
if (current->dx > 0) {
xx[k] = fmin(adjacent_line_x, adjacent_line_x_other_edge);
} else {
xx[k] = fmax(adjacent_line_x, adjacent_line_x_other_edge) + 1;
}
}
break;
}
}
}
}
}
qsort(xx, j, sizeof(float), x_cmp);