Joining bezier curve to other drawings

Question

I have implemented a rounded rectangle extension method, defined here.

public static Graphics DrawRRectangle(this Graphics g, Pen p, int x, int y, int width, int height, int feathering)
    {
        g.DrawLine(p, x, y + feathering, x, y + height - feathering);
        g.DrawBezier(p, new Point(x, y + height - feathering),
                        new Point(x, y + height - feathering / 2), new Point(x + feathering / 2, y + height),
                        new Point(x + feathering, y + height));

        g.DrawLine(p, x + feathering, y + height , x + width - feathering, y + height);
        g.DrawBezier(p, new Point(x + width - feathering, y + height),
                        new Point(x + width - feathering / 2, y + height), new Point(x + width, y + height - feathering / 2),
                        new Point(x + width, y + height - feathering));

        g.DrawLine(p, x + width, y + height - feathering, x + width, y + feathering);
        g.DrawBezier(p, new Point(x + width, y + feathering),
                        new Point(x + width, y + feathering / 2), new Point(x + width - feathering / 2, y),
                        new Point(x + width - feathering, y));

        g.DrawLine(p, x + width - feathering, y, x + feathering, y);
        g.DrawBezier(p, new Point(x + feathering, y),
                        new Point(x + feathering / 2, y), new Point(x, y + feathering / 2),
                        new Point(x, y + feathering));
        return g;
    }

However when I use this method like so g.DrawRRectangle(p, 100, 100, 1000, 1000, 100);, I do not get the outcome I wanted, each of the corners are either misaligned of their pixels do not match up As seen in the images below.

Any suggestions anybody could offer would be helpful, I am unsure if this is a problem with the equations used to generate my curves however this is the first time I am dabbling with graphics, so it could just be my thinking. Thanks.

https://web.archive.org/web/20111110163706/http://www.switchonthecode.com/tutorials/csharp-creating-rounded-rectangles-using-a-graphics-path — Matthew Layton, May 02 '17 at 10:38
http://stackoverflow.com/questions/19167463/oddly-drawn-graphicspath-with-graphics-fillpath — Matthew Layton, May 02 '17 at 10:38
I tried that first links implementation however I am confused about this enum logic, I get errors with the syntax for each of the enum conditionals. `RectangleCorners.TopLeft & corners == RectangleCorners.TopLeft` it says that the & operand cannot be applied — Curtis, May 02 '17 at 12:21
an enum is a poor way to determine which corners should be rounded. Try the second example instead as this uses a BorderRadius class, which allows you to specify the rounding amount for each corner individually. — Matthew Layton, May 02 '17 at 12:23
Thanks, you can provide the second link as an answer and say we discussed it in the comments if you want the accepted answer. — Curtis, May 02 '17 at 13:16
`RectangleCorners.TopLeft & corners == RectangleCorners.TopLeft` works if you wrap the first logical and operation in parenthesis: `(RectangleCorners.TopLeft & corners) == RectangleCorners.TopLeft` Or you could use `Enum.HasFlag` https://msdn.microsoft.com/en-us/library/system.enum.hasflag(v=vs.110).aspx — Matthew Layton, May 02 '17 at 13:20

score 2 · Accepted Answer · edited May 23 '17 at 12:34

Whilst I can't comment on your implementation, you're going to run into problems further down the road with this. Your implementation will give the appearance of drawing a rounded rectangle, but say for example in future you want to fill the shape, you won't be able to because GDI/GDI+ won't see the drawn shapes as a single consecutive shape.

In this respect you should use a GraphicsPath.

See here for a complete solution for drawing rounded rectangles using a GraphicsPath.

Joining bezier curve to other drawings

1 Answers1