Use mask in C when drawing wide polygon lines

src/PIL/ImageDraw.py

@@ -365,22 +365,10 @@ def polygon(
                 # 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(mask)
                 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)
+                self.draw.draw_polygon(xy, ink, 0, width * 2 - 1, mask.im)
 
     def regular_polygon(
         self,

src/_imaging.c

@@ -3220,7 +3220,8 @@
                     (int)p[3],
                     &ink,
                     width,
-                    self->blend
+                    self->blend,
+                    NULL
                 ) < 0) {
                 free(xy);
                 return NULL;
@@ -3358,7 +3359,10 @@
     int ink;
     int fill = 0;
     int width = 0;
-    if (!PyArg_ParseTuple(args, "Oi|ii", &data, &ink, &fill, &width)) {
+    ImagingObject *maskp = NULL;
+    if (!PyArg_ParseTuple(
+            args, "Oi|iiO!", &data, &ink, &fill, &width, &Imaging_Type, &maskp
+        )) {
         return NULL;
     }
 
@@ -3388,8 +3392,16 @@
 
     free(xy);
 
-    if (ImagingDrawPolygon(self->image->image, n, ixy, &ink, fill, width, self->blend) <
-        0) {
+    if (ImagingDrawPolygon(
+            self->image->image,
+            n,
+            ixy,
+            &ink,
+            fill,
+            width,
+            self->blend,
+            maskp ? maskp->image : NULL
+        ) < 0) {
         free(ixy);
         return NULL;
     }

src/libImaging/Draw.c

@@ -63,7 +63,7 @@
 } Edge;
 
 /* Type used in "polygon*" functions */
-typedef void (*hline_handler)(Imaging, int, int, int, int);
+typedef void (*hline_handler)(Imaging, int, int, int, int, Imaging);
 
 static inline void
 point8(Imaging im, int x, int y, int ink) {
@@ -103,7 +103,7 @@
 }
 
 static inline void
-hline8(Imaging im, int x0, int y0, int x1, int ink) {
+hline8(Imaging im, int x0, int y0, int x1, int ink, Imaging mask) {
     int pixelwidth;
 
     if (y0 >= 0 && y0 < im->ysize) {
@@ -119,15 +119,30 @@
         }
         if (x0 <= x1) {
             pixelwidth = strncmp(im->mode, "I;16", 4) == 0 ? 2 : 1;
-            memset(
-                im->image8[y0] + x0 * pixelwidth, (UINT8)ink, (x1 - x0 + 1) * pixelwidth
-            );
+            if (mask == NULL) {
+                memset(
+                    im->image8[y0] + x0 * pixelwidth,
+                    (UINT8)ink,
+                    (x1 - x0 + 1) * pixelwidth
+                );
+            } else {
+                UINT8 *p = im->image8[y0];
+                while (x0 <= x1) {
+                    if (mask->image8[y0][x0]) {
+                        p[x0 * pixelwidth] = ink;
+                        if (pixelwidth == 2) {
+                            p[x0 * pixelwidth + 1] = ink;
+                        }
+                    }
+                    x0++;
+                }
+            }
         }
     }
 }
 
 static inline void
-hline32(Imaging im, int x0, int y0, int x1, int ink) {
+hline32(Imaging im, int x0, int y0, int x1, int ink, Imaging mask) {
     INT32 *p;
 
     if (y0 >= 0 && y0 < im->ysize) {
@@ -143,13 +158,16 @@
         }
         p = im->image32[y0];
         while (x0 <= x1) {
-            p[x0++] = ink;
+            if (mask == NULL || mask->image8[y0][x0]) {
+                p[x0] = ink;
+            }
+            x0++;
         }
     }
 }
 
 static inline void
-hline32rgba(Imaging im, int x0, int y0, int x1, int ink) {
+hline32rgba(Imaging im, int x0, int y0, int x1, int ink, Imaging mask) {
     unsigned int tmp;
 
     if (y0 >= 0 && y0 < im->ysize) {
@@ -167,9 +185,11 @@
             UINT8 *out = (UINT8 *)im->image[y0] + x0 * 4;
             UINT8 *in = (UINT8 *)&ink;
             while (x0 <= x1) {
-                out[0] = BLEND(in[3], out[0], in[0], tmp);
-                out[1] = BLEND(in[3], out[1], in[1], tmp);
-                out[2] = BLEND(in[3], out[2], in[2], tmp);
+                if (mask == NULL || mask->image8[y0][x0]) {
+                    out[0] = BLEND(in[3], out[0], in[0], tmp);
+                    out[1] = BLEND(in[3], out[1], in[1], tmp);
+                    out[2] = BLEND(in[3], out[2], in[2], tmp);
+                }
                 x0++;
                 out += 4;
             }
@@ -407,7 +427,14 @@
 
 static void
 draw_horizontal_lines(
-    Imaging im, int n, Edge *e, int ink, int *x_pos, int y, hline_handler hline
+    Imaging im,
+    int n,
+    Edge *e,
+    int ink,
+    int *x_pos,
+    int y,
+    hline_handler hline,
+    Imaging mask
 ) {
     int i;
     for (i = 0; i < n; i++) {
@@ -429,7 +456,7 @@
                 }
             }
 
-            (*hline)(im, xmin, e[i].ymin, xmax, ink);
+            (*hline)(im, xmin, e[i].ymin, xmax, ink, mask);
             *x_pos = xmax + 1;
         }
     }
@@ -439,7 +466,9 @@
  * Filled polygon draw function using scan line algorithm.
  */
 static inline int
-polygon_generic(Imaging im, int n, Edge *e, int ink, int eofill, hline_handler hline) {
+polygon_generic(
+    Imaging im, int n, Edge *e, int ink, int eofill, hline_handler hline, Imaging mask
+) {
     Edge **edge_table;
     float *xx;
     int edge_count = 0;
@@ -469,7 +498,7 @@
         }
         if (e[i].ymin == e[i].ymax) {
             if (hasAlpha != 1) {
-                (*hline)(im, e[i].xmin, e[i].ymin, e[i].xmax, ink);
+                (*hline)(im, e[i].xmin, e[i].ymin, e[i].xmax, ink, mask);
             }
             continue;
         }
@@ -557,7 +586,7 @@
                     // Line would be before the current position
                     continue;
                 }
-                draw_horizontal_lines(im, n, e, ink, &x_pos, ymin, hline);
+                draw_horizontal_lines(im, n, e, ink, &x_pos, ymin, hline, mask);
                 if (x_end < x_pos) {
                     // Line would be before the current position
                     continue;
@@ -573,13 +602,13 @@
                         continue;
                     }
                 }
-                (*hline)(im, x_start, ymin, x_end, ink);
+                (*hline)(im, x_start, ymin, x_end, ink, mask);
                 x_pos = x_end + 1;
             }
-            draw_horizontal_lines(im, n, e, ink, &x_pos, ymin, hline);
+            draw_horizontal_lines(im, n, e, ink, &x_pos, ymin, hline, mask);
         } else {
             for (i = 1; i < j; i += 2) {
-                (*hline)(im, ROUND_UP(xx[i - 1]), ymin, ROUND_DOWN(xx[i]), ink);
+                (*hline)(im, ROUND_UP(xx[i - 1]), ymin, ROUND_DOWN(xx[i]), ink, mask);
             }
         }
     }
@@ -623,7 +652,7 @@
 
 typedef struct {
     void (*point)(Imaging im, int x, int y, int ink);
-    void (*hline)(Imaging im, int x0, int y0, int x1, int ink);
+    void (*hline)(Imaging im, int x0, int y0, int x1, int ink, Imaging mask);
     void (*line)(Imaging im, int x0, int y0, int x1, int y1, int ink);
 } DRAW;
 
@@ -674,7 +703,15 @@
 
 int
 ImagingDrawWideLine(
-    Imaging im, int x0, int y0, int x1, int y1, const void *ink_, int width, int op
+    Imaging im,
+    int x0,
+    int y0,
+    int x1,
+    int y1,
+    const void *ink_,
+    int width,
+    int op,
+    Imaging mask
 ) {
     DRAW *draw;
     INT32 ink;
@@ -714,7 +751,7 @@
         add_edge(e + 2, vertices[2][0], vertices[2][1], vertices[3][0], vertices[3][1]);
         add_edge(e + 3, vertices[3][0], vertices[3][1], vertices[0][0], vertices[0][1]);
 
-        polygon_generic(im, 4, e, ink, 0, draw->hline);
+        polygon_generic(im, 4, e, ink, 0, draw->hline, mask);
     }
     return 0;
 }
@@ -757,7 +794,7 @@
         }
 
         for (y = y0; y <= y1; y++) {
-            draw->hline(im, x0, y, x1, ink);
+            draw->hline(im, x0, y, x1, ink, NULL);
         }
 
     } else {
@@ -766,8 +803,8 @@
             width = 1;
         }
         for (i = 0; i < width; i++) {
-            draw->hline(im, x0, y0 + i, x1, ink);
-            draw->hline(im, x0, y1 - i, x1, ink);
+            draw->hline(im, x0, y0 + i, x1, ink, NULL);
+            draw->hline(im, x0, y1 - i, x1, ink, NULL);
             draw->line(im, x1 - i, y0 + width, x1 - i, y1 - width + 1, ink);
             draw->line(im, x0 + i, y0 + width, x0 + i, y1 - width + 1, ink);
         }
@@ -778,7 +815,14 @@
 
 int
 ImagingDrawPolygon(
-    Imaging im, int count, int *xy, const void *ink_, int fill, int width, int op
+    Imaging im,
+    int count,
+    int *xy,
+    const void *ink_,
+    int fill,
+    int width,
+    int op,
+    Imaging mask
 ) {
     int i, n, x0, y0, x1, y1;
     DRAW *draw;
@@ -822,7 +866,7 @@
         if (xy[i * 2] != xy[0] || xy[i * 2 + 1] != xy[1]) {
             add_edge(&e[n++], xy[i * 2], xy[i * 2 + 1], xy[0], xy[1]);
         }
-        polygon_generic(im, n, e, ink, 0, draw->hline);
+        polygon_generic(im, n, e, ink, 0, draw->hline, mask);
         free(e);
 
     } else {
@@ -844,11 +888,12 @@
                     xy[i * 2 + 3],
                     ink_,
                     width,
-                    op
+                    op,
+                    mask
                 );
             }
             ImagingDrawWideLine(
-                im, xy[i * 2], xy[i * 2 + 1], xy[0], xy[1], ink_, width, op
+                im, xy[i * 2], xy[i * 2 + 1], xy[0], xy[1], ink_, width, op, mask
             );
         }
     }
@@ -1519,7 +1564,9 @@
     ellipse_init(&st, a, b, width);
     int32_t X0, Y, X1;
     while (ellipse_next(&st, &X0, &Y, &X1) != -1) {
-        draw->hline(im, x0 + (X0 + a) / 2, y0 + (Y + b) / 2, x0 + (X1 + a) / 2, ink);
+        draw->hline(
+            im, x0 + (X0 + a) / 2, y0 + (Y + b) / 2, x0 + (X1 + a) / 2, ink, NULL
+        );
     }
     return 0;
 }
@@ -1554,7 +1601,9 @@
     int32_t X0, Y, X1;
     int next_code;
     while ((next_code = clip_ellipse_next(&st, &X0, &Y, &X1)) >= 0) {
-        draw->hline(im, x0 + (X0 + a) / 2, y0 + (Y + b) / 2, x0 + (X1 + a) / 2, ink);
+        draw->hline(
+            im, x0 + (X0 + a) / 2, y0 + (Y + b) / 2, x0 + (X1 + a) / 2, ink, NULL
+        );
     }
     clip_ellipse_free(&st);
     return next_code == -1 ? 0 : -1;
@@ -1972,7 +2021,7 @@
 
     DRAWINIT();
 
-    polygon_generic(im, outline->count, outline->edges, ink, 0, draw->hline);
+    polygon_generic(im, outline->count, outline->edges, ink, 0, draw->hline, NULL);
 
     return 0;
 }

src/libImaging/Imaging.h

@@ -510,7 +510,15 @@ extern int
 ImagingDrawLine(Imaging im, int x0, int y0, int x1, int y1, const void *ink, int op);
 extern int
 ImagingDrawWideLine(
-    Imaging im, int x0, int y0, int x1, int y1, const void *ink, int width, int op
+    Imaging im,
+    int x0,
+    int y0,
+    int x1,
+    int y1,
+    const void *ink,
+    int width,
+    int op,
+    Imaging mask
 );
 extern int
 ImagingDrawPieslice(
@@ -530,7 +538,14 @@ 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 width, int op
+    Imaging im,
+    int points,
+    int *xy,
+    const void *ink,
+    int fill,
+    int width,
+    int op,
+    Imaging mask
 );
 extern int
 ImagingDrawRectangle(