Rounded corners with C++ - c++

Question

I'm looking for some c++ drawing graphics library to create rounded corners with anti-aliasing option for dynamic keyboard key creator. I've already tested OpenCV and Magick++ functions but the result was not so good. Can anyone help me with this?
This is a sample of one code to create a rounded corner with Magick++ library
void create_rounded_image (int size, int border) {
Magick::Image image_bk (Magick::Geometry (size, size), Magick::Color ("black"));
image_bk.strokeColor ("white");
image_bk.fillColor ("white");
image_bk.strokeWidth(1);
image_bk.draw (DrawableCircle(size, size, size*0.3, size*0.3));
image_bk.write ("rounded.png");
}
This is the result I'm getting
This is the result I'm looking for

Answer 1

Googling some online documentation, I found:
strokeAntiAlias - bool - Enable or disable anti-aliasing when drawing object outlines.
I suggest:
image_bk.strokeAntiAlias(true);

Answer 2

Expanding on Lamar's answer. Magick::Image.strokeAntiAlias and Magick::DrawableStrokeAntiAlias is what you want. But I would suggest using std::list<Drawable> to generate a context stack. This would allow your application to manage what-will-be-drawn independently of image i/o.
using namespace Magick;
size_t size = 405;
size_t border = 6;
std::list<Drawable> ctx;
ctx.push_back(DrawableStrokeAntialias(MagickTrue));
ctx.push_back(DrawableStrokeColor("#CAF99B"));
ctx.push_back(DrawableStrokeWidth(border));
ctx.push_back(DrawableFillColor("#68C77B"));
ctx.push_back(DrawableCircle(size*0.75, size*0.25, size*0.33, size*0.66));
Image image_bk( Geometry(size, size), Color("white"));
image_bk.draw(ctx);