generate image for stroke width 2.0 and 3.0 on C++

gen_polyline.cpp

#include <stdio.h>
#include <Magick++.h>
using namespace Magick;


void gen_line_png(float line_width)
{
    Image image = Image(Geometry(200, 200), Color("white"));
    char filename[50];
    CoordinateList coords;
    DrawableList drawables;
    Color blankColor;
    Color ptColor = Color("magenta");
    Color lineColor = Color("red");

    image.type(TrueColorMatteType);

    drawables.push_back(DrawableFillColor(ptColor));
    drawables.push_back(DrawableStrokeColor(ptColor));

    int i, x, y, height, width;
    float r = 1.0;
    height = image.size().height();
    width = image.size().width();

    int v[6][2] = {{50,50}, {75,60}, {100,80}, {150,150}, {150,30}, {180,10}};

    for (i = 0; i < 6; ++i) {
        x = v[i][0]; y = v[i][1];
        coords.push_back(Coordinate(x, height - y));
        y = height - y;
        drawables.push_back(DrawableCircle(x, y, x + r, y + r));
    }

    drawables.push_back(DrawableFillColor(blankColor));
    drawables.push_back(DrawableStrokeColor(lineColor));
    drawables.push_back(DrawableStrokeLineJoin(RoundJoin));
    drawables.push_back(DrawableStrokeWidth(line_width));
    drawables.push_back(DrawablePolyline(coords));

    image.draw(drawables);

    sprintf(filename, "test-im%d.png", int(line_width));
    image.write(filename);
}

int main(int argc, char **argv)
{
    InitializeMagick(*argv);

    gen_line_png(2.0);
    gen_line_png(3.0);

    return 0;
}