Add gdImageAAline (antialiased line)

Add AA support for gdImagePolygon

ext/gd/libgd/gd.c

@@ -1037,6 +1037,134 @@ gdImageLine (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
 	}
     }
 }
+
+
+#define BLEND_COLOR(a, nc, c, cc) \
+nc = (cc) + (((((c) - (cc)) * (a)) + ((((c) - (cc)) * (a)) >> 8) + 0x80) >> 8);
+
+inline static void gdImageSetAAPixelColor(gdImagePtr im, int x, int y, int color, int t)
+{
+	int dr,dg,db,p,r,g,b;
+	dr = gdTrueColorGetRed(color);
+	dg = gdTrueColorGetGreen(color);
+	db = gdTrueColorGetBlue(color);
+
+	p = gdImageGetPixel(im,x,y);
+	r = gdTrueColorGetRed(p);
+	g = gdTrueColorGetGreen(p);
+	b = gdTrueColorGetBlue(p);
+
+	BLEND_COLOR(t, dr, r, dr);
+	BLEND_COLOR(t, dg, g, dg);
+	BLEND_COLOR(t, db, b, db);
+	im->tpixels[y][x]=gdTrueColorAlpha(dr, dg, db,  gdAlphaOpaque);
+}  
+
+void gdImageAALine (gdImagePtr im, int x1, int y1, int x2, int y2, int col)
+{
+/* keep them as 32bits */
+long x, y, inc;
+	long dx, dy,tmp;
+
+	if (y1 < 0 && y2 < 0) {
+		return;
+	}
+	if (y1 < 0) {
+	x1 += (y1 * (x1 - x2)) / (y2 - y1);
+		y1 = 0;
+	}
+	if (y2 < 0) {
+		x2 += (y2 * (x1 - x2)) / (y2 - y1);
+	y2 = 0;
+	}
+
+	/* bottom edge */
+	if (y1 >= im->sy && y2 >= im->sy) {
+		return;
+	}
+	if (y1 >= im->sy) {
+		x1 -= ((im->sy - y1) * (x1 - x2)) / (y2 - y1);
+		y1 = im->sy - 1;
+	}
+	if (y2 >= im->sy) {
+		x2 -= ((im->sy - y2) * (x1 - x2)) / (y2 - y1);
+		y2 = im->sy - 1;
+	}
+
+	/* left edge */
+	if (x1 < 0 && x2 < 0) {
+		return;
+	}
+	if (x1 < 0) {
+		y1 += (x1 * (y1 - y2)) / (x2 - x1);
+		x1 = 0;
+	}
+	if (x2 < 0) {
+		y2 += (x2 * (y1 - y2)) / (x2 - x1);
+		x2 = 0;
+	}
+	/* right edge */
+	if (x1 >= im->sx && x2 >= im->sx) {
+		return;
+	}
+	if (x1 >= im->sx) {
+		y1 -= ((im->sx - x1) * (y1 - y2)) / (x2 - x1);
+		x1 = im->sx - 1;
+	}
+	if (x2 >= im->sx) {
+		y2 -= ((im->sx - x2) * (y1 - y2)) / (x2 - x1);
+		x2 = im->sx - 1;
+	}
+
+	dx = x2 - x1;
+	dy = y2 - y1;
+
+	if (dx == 0 && dy == 0) {
+		return;
+	}
+	if (abs(dx) > abs(dy)) {
+		if (dx < 0) {
+			tmp = x1;
+			x1 = x2;
+			x2 = tmp;
+			tmp = y1;
+			y1 = y2;
+			y2 = tmp;
+			dx = x2 - x1;
+			dy = y2 - y1;
+		}
+		x = x1 << 16;
+		y = y1 << 16;
+		inc = (dy * 65536) / dx;
+		while ((x >> 16) < x2) {
+			gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (y >> 8) & 0xFF);
+			gdImageSetAAPixelColor(im, x >> 16, (y >> 16) + 1,col, (~y >> 8) & 0xFF);
+			x += (1 << 16);
+			y += inc;
+		}
+	} else {
+		if (dy < 0) {
+			tmp = x1;
+			x1 = x2;
+			x2 = tmp;
+			tmp = y1;
+			y1 = y2;
+			y2 = tmp;
+			dx = x2 - x1;
+			dy = y2 - y1;
+		}
+		x = x1 << 16;
+		y = y1 << 16;
+		inc = (dx * 65536) / dy;
+		while ((y>>16) < y2) {
+			gdImageSetAAPixelColor(im, x >> 16, y >> 16, col, (x >> 8) & 0xFF);
+			gdImageSetAAPixelColor(im, (x >> 16) + 1, (y >> 16),col, (~x >> 8) & 0xFF);
+			x += inc;
+			y += (1<<16);
+		}
+	}
+}
+
 static void dashedSet (gdImagePtr im, int x, int y, int color,
 		       int *onP, int *dashStepP, int wid, int vert);
 
@@ -2778,17 +2906,23 @@ gdImagePolygon (gdImagePtr im, gdPointPtr p, int n, int c)
 {
 	int i;
 	int lx, ly;
-  if (!n)
+	typedef void (*image_line)(gdImagePtr im, int x1, int y1, int x2, int y2, int color);
-    {
+	image_line draw_line;
+
+	if (!n) {
 		return;
 	}
+	if ( im->antialias) {
+		draw_line = gdImageAALine;
+	} else {
+		draw_line = gdImageLine;
+	}
 	lx = p->x;
 	ly = p->y;
-  gdImageLine (im, lx, ly, p[n - 1].x, p[n - 1].y, c);
+	draw_line(im, lx, ly, p[n - 1].x, p[n - 1].y, c);
-  for (i = 1; (i < n); i++)
+	for (i = 1; (i < n); i++) {
-    {
 		p++;
-      gdImageLine (im, lx, ly, p->x, p->y, c);
+		draw_line(im, lx, ly, p->x, p->y, c);
 		lx = p->x;
 		ly = p->y;
 	}
@@ -3082,6 +3216,12 @@ gdImageAlphaBlending (gdImagePtr im, int alphaBlendingArg)
   im->alphaBlendingFlag = alphaBlendingArg;
 }
 
+void
+gdImageAntialias (gdImagePtr im, int antialias)
+{
+	im->antialias = antialias;
+}
+
 void
 gdImageSaveAlpha (gdImagePtr im, int saveAlphaArg)
 {