Added line width argument to ImageDraw polygon

Tests/test_imagedraw.py

@@ -945,6 +945,18 @@ def test_triangle_right():
     )
 
 
+@pytest.mark.parametrize(
+    "fill, suffix",
+    ((BLACK, "width"), (None, "width_no_fill")),
+)
+def test_triangle_right_width(fill, suffix):
+    img, draw = create_base_image_draw((100, 100))
+    draw.polygon([(15, 25), (85, 25), (50, 60)], fill, WHITE, width=5)
+    assert_image_equal_tofile(
+        img, os.path.join(IMAGES_PATH, "triangle_right_" + suffix + ".png")
+    )
+
+
 def test_line_horizontal():
     img, draw = create_base_image_draw((20, 20))
     draw.line((5, 5, 14, 5), BLACK, 2)

src/PIL/ImageDraw.py

@@ -233,13 +233,35 @@ def point(self, xy, fill=None):
         if ink is not None:
             self.draw.draw_points(xy, ink)
 
-    def polygon(self, xy, fill=None, outline=None):
+    def polygon(self, xy, fill=None, outline=None, width=1):
         """Draw a polygon."""
         ink, fill = self._getink(outline, fill)
         if fill is not None:
             self.draw.draw_polygon(xy, fill, 1)
-        if ink is not None and ink != fill:
-            self.draw.draw_polygon(xy, ink, 0)
+        if ink is not None and ink != fill and width != 0:
+            if width == 1:
+                self.draw.draw_polygon(xy, ink, 0, width)
+            else:
+                # To avoid expanding the polygon outwards,
+                # use the fill as a mask
+                mask = Image.new("1", self.im.size)
+                mask_ink = self._getink(1)[0]
+
+                fill_im = mask.copy()
+                draw = Draw(fill_im)
+                draw.draw.draw_polygon(xy, mask_ink, 1)
+
+                ink_im = mask.copy()
+                draw = Draw(ink_im)
+                width = width * 2 - 1
+                draw.draw.draw_polygon(xy, mask_ink, 0, width)
+
+                mask.paste(ink_im, mask=fill_im)
+
+                im = Image.new(self.mode, self.im.size)
+                draw = Draw(im)
+                draw.draw.draw_polygon(xy, ink, 0, width)
+                self.im.paste(im.im, (0, 0) + im.size, mask.im)
 
     def regular_polygon(
         self, bounding_circle, n_sides, rotation=0, fill=None, outline=None

src/_imaging.c

@@ -3124,7 +3124,8 @@ _draw_polygon(ImagingDrawObject *self, PyObject *args) {
     PyObject *data;
     int ink;
     int fill = 0;
-    if (!PyArg_ParseTuple(args, "Oi|i", &data, &ink, &fill)) {
+    int width = 0;
+    if (!PyArg_ParseTuple(args, "Oi|ii", &data, &ink, &fill, &width)) {
         return NULL;
     }
 
@@ -3153,7 +3154,7 @@ _draw_polygon(ImagingDrawObject *self, PyObject *args) {
 
     free(xy);
 
-    if (ImagingDrawPolygon(self->image->image, n, ixy, &ink, fill, self->blend) < 0) {
+    if (ImagingDrawPolygon(self->image->image, n, ixy, &ink, fill, width, self->blend) < 0) {
         free(ixy);
         return NULL;
     }

src/libImaging/Draw.c

@@ -742,7 +742,7 @@ ImagingDrawRectangle(
 }
 
 int
-ImagingDrawPolygon(Imaging im, int count, int *xy, const void *ink_, int fill, int op) {
+ImagingDrawPolygon(Imaging im, int count, int *xy, const void *ink_, int fill, int width, int op) {
     int i, n, x0, y0, x1, y1;
     DRAW *draw;
     INT32 ink;
@@ -790,10 +790,17 @@ ImagingDrawPolygon(Imaging im, int count, int *xy, const void *ink_, int fill, i
 
     } else {
         /* Outline */
-        for (i = 0; i < count - 1; i++) {
-            draw->line(im, xy[i * 2], xy[i * 2 + 1], xy[i * 2 + 2], xy[i * 2 + 3], ink);
+        if (width == 1) {
+            for (i = 0; i < count - 1; i++) {
+                draw->line(im, xy[i * 2], xy[i * 2 + 1], xy[i * 2 + 2], xy[i * 2 + 3], ink);
+            }
+            draw->line(im, xy[i * 2], xy[i * 2 + 1], xy[0], xy[1], ink);
+        } else {
+            for (i = 0; i < count - 1; i++) {
+                ImagingDrawWideLine(im, xy[i * 2], xy[i * 2 + 1], xy[i * 2 + 2], xy[i * 2 + 3], ink_, width, op);
+            }
+            ImagingDrawWideLine(im, xy[i * 2], xy[i * 2 + 1], xy[0], xy[1], ink_, width, op);
         }
-        draw->line(im, xy[i * 2], xy[i * 2 + 1], xy[0], xy[1], ink);
     }
 
     return 0;

src/libImaging/Imaging.h

@@ -487,7 +487,7 @@ ImagingDrawPieslice(
 extern int
 ImagingDrawPoint(Imaging im, int x, int y, const void *ink, int op);
 extern int
-ImagingDrawPolygon(Imaging im, int points, int *xy, const void *ink, int fill, int op);
+ImagingDrawPolygon(Imaging im, int points, int *xy, const void *ink, int fill, int width, int op);
 extern int
 ImagingDrawRectangle(
     Imaging im,