optimise: fill QRCode with one colour (#626)

Author: TimothyMakkison

QRCoder/QRCode.cs

@@ -62,6 +62,7 @@ public Bitmap GetGraphic(int pixelsPerModule, Color darkColor, Color lightColor,
         using (var lightBrush = new SolidBrush(lightColor))
         using (var darkBrush = new SolidBrush(darkColor))
         {
+            gfx.FillRectangle(lightBrush, new Rectangle(0, 0, bmp.Width, bmp.Height));
             for (var x = 0; x < size + offset; x += pixelsPerModule)
             {
                 for (var y = 0; y < size + offset; y += pixelsPerModule)
@@ -72,10 +73,6 @@ public Bitmap GetGraphic(int pixelsPerModule, Color darkColor, Color lightColor,
                     {
                         gfx.FillRectangle(darkBrush, new Rectangle(x - offset, y - offset, pixelsPerModule, pixelsPerModule));
                     }
-                    else
-                    {
-                        gfx.FillRectangle(lightBrush, new Rectangle(x - offset, y - offset, pixelsPerModule, pixelsPerModule));
-                    }
                 }
             }