image-surface.cc

An example of using Cairo::ImageSurface class to render to PNG

/* M_PI is defined in math.h in the case of Microsoft Visual C++, Solaris,
 * et. al.
 */
#if defined(_MSC_VER)
#define _USE_MATH_DEFINES
#endif 

#include <string>
#include <iostream>
#include <cairommconfig.h>
#include <cairomm/context.h>
#include <cairomm/surface.h>

#include <cmath>

int main()
{
    auto surface =
        Cairo::ImageSurface::create(Cairo::FORMAT_ARGB32, 600, 400);

    auto cr = Cairo::Context::create(surface);

    cr->save(); // save the state of the context
    cr->set_source_rgb(0.86, 0.85, 0.47);
    cr->paint();    // fill image with the color
    cr->restore();  // color is back to black now

    cr->save();
    // draw a border around the image
    cr->set_line_width(20.0);    // make the line wider
    cr->rectangle(0.0, 0.0, surface->get_width(), surface->get_height());
    cr->stroke();

    cr->set_source_rgba(0.0, 0.0, 0.0, 0.7);
    // draw a circle in the center of the image
    cr->arc(surface->get_width() / 2.0, surface->get_height() / 2.0, 
            surface->get_height() / 4.0, 0.0, 2.0 * M_PI);
    cr->stroke();

    // draw a diagonal line
    cr->move_to(surface->get_width() / 4.0, surface->get_height() / 4.0);
    cr->line_to(surface->get_width() * 3.0 / 4.0, surface->get_height() * 3.0 / 4.0);
    cr->stroke();
    cr->restore();

#ifdef CAIRO_HAS_PNG_FUNCTIONS

    std::string filename = "image.png";
    surface->write_to_png(filename);

    std::cout << "Wrote png file \"" << filename << "\"" << std::endl;

#else

    std::cout << "You must compile cairo with PNG support for this example to work."
        << std::endl;

#endif
}