Hello, I apologize if this is off-topic as it deals a lot with Cairo,
I feel it is a borderline thing. Please feel free to send me packing
to somewhere else if I'm wrong on that point :-)
I'm trying to load an image into a DrawingArea, then put lines on it
with Cairo and get that back out. Is this possible or do I need to go
figure out something with GC and Drawable?
Here's the guts of the procedure so far, sorry it's big but I don't
know how to trim it down and keep it understandable.
---------------------------------------------
class ExampleWindow : public Gtk::Window {
public:
ExampleWindow (std::string path) {
imagePB = Gdk::Pixbuf::create_from_file(path);
drawOnMe.signal_expose_event().connect(sigc::mem_fun(*this,&ExampleWindow::on_da_expose_event));
add(drawOnMe);
show_all();
}
private:
Gtk::DrawingArea drawOnMe;
Glib::RefPtr<Gdk::Pixbuf> imagePB;
bool on_da_expose_event (GdkEventExpose * event) {
std::cout << "Expose Event" << std::endl;
Glib::RefPtr<Gdk::Window> window =
drawOnMe.get_window();
Cairo::RefPtr<Cairo::Context> context =
window->create_cairo_context();
Cairo::RefPtr<Cairo::ImageSurface> image_surface =
Cairo::ImageSurface::create (Cairo::FORMAT_RGB24,
imagePB->get_width(), imagePB->get_height());
Cairo::RefPtr<Cairo::Context> image_context =
Cairo::Context::create(image_surface);
Gdk::Cairo::set_source_pixbuf (image_context, imagePB,
0.0, 0.0);
image_context->paint();
context->set_source(image_surface, 0.0, 0.0);
context->paint();
context->set_line_width(5.0);
context->set_source_rgb(0.8, 0.0, 0.0);
context->move_to(10,20);
context->line_to(100, 200);
context->stroke();
return false;
}
};
---------------------------------------------
I tried getting a surface from that context after the stroke() call
and then a write to PNG:
Cairo::RefPtr<Cairo::Surface> sfc = context->get_target();
sfc->write_to_png("please_work.png");
That just crashed on an expose event and I didn't bother to debug. I
have the feeling I've gone wrong in my understanding of Cairo.
So I guess what it boils down to is I'm curious if there is an easier
path by using something in Gtkmm (which I chased my tail for a long
time trying to find something) or if there is a way to get that drawn
data back out of there.
Thanks for any and all help :-)
- John Hobbs
[EMAIL PROTECTED]
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