[cairo] Regarding saving a image surface as PNG

[Gerdus van Zyl]

You can use get_target anywhere in on_expose, the write_to_png should be
where it is now, after all painting is done before destroy.

On Wed, Apr 16, 2008 at 2:09 PM, Chandra Shekhar Sengupta <
sayan801 at gmail.com> wrote:

>
>
> Hi,
>
> i have tried with following code
>
> tsurf = cairo_get_target(cr);
> cairo_surface_write_to_png (tsurf, "sticker.png");
>
> but it is saving a zero Byte PNG. Could you tell me where to use
> "cairo_get_target" api ?
>
> Thanks in Advance.
>
> Regards,
> Chandra Shekhar Sengupta
>
>
> On Wed, Apr 16, 2008 at 3:34 PM, Gerdus van Zyl <gerdusvanzyl at gmail.com>
> wrote:
>
> > Its because you are not working with the surface cr is targeting. You
> > need code like
> > tsurf = cairo_get_target(cr); to get the temporary surface GTK is giving
> > you.
> >
> > ~Gerdus
> >
> > On Wed, Apr 16, 2008 at 8:11 AM, Chandra Shekhar Sengupta <
> > sayan801 at gmail.com> wrote:
> >
> > > Hi,
> > > I am new to cairo. i am trying to rotate and scale a image . After
> > > doing the transformation i am displaying it in the window, it is shown
> > > properly . But when i am saving the surface using
> > > "cairo_surface_write_to_png" , the original image is saved again , the
> > > changes due to transformation is not reflected. And when i was trying to get
> > > the width of scaled surface using "cairo_image_surface_get_width", it is
> > > giving the original width only.My code segment is given below.
> > >
> > > /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
> > >
> > > static gboolean on_expose_event(GtkWidget *widget,GdkEventExpose
> > > *event, gpointer data)
> > > {
> > >   cairo_t *cr;
> > > gint width,height;
> > >
> > > cr = gdk_cairo_create (widget->window);
> > >
> > > width = cairo_image_surface_get_width(image);
> > > height = cairo_image_surface_get_height(image);
> > >
> > >
> > > cairo_translate(cr,width/2,height/2);
> > >
> > > cairo_scale(cr,scale_factor,scale_factor);
> > >
> > > cairo_rotate(cr,rotate_angle*M_PI/180.0);
> > >
> > >  g_print("rotate_angle %f \n",rotate_angle);
> > >
> > >
> > > gtk_widget_set_size_request (da, width,height);
> > >
> > >  g_print("width = %d height = %d \n",width,height);
> > >
> > >  cairo_set_source_surface(cr, image,-width/2,-height/2);
> > >
> > >  cairo_paint(cr);
> > >  cairo_surface_write_to_png (image, "sticker.png");
> > >
> > >   cairo_destroy(cr);
> > >
> > >   return FALSE;
> > > }
> > >
> > >
> > > int main(int argc, char *argv[])
> > > {
> > >   /...../
> > >
> > >   image = cairo_image_surface_create_from_png(argv[1]);
> > >   width = cairo_image_surface_get_width(image);
> > >   height = cairo_image_surface_get_height(image);
> > >  g_print("width = %d height = %d \n",width,height);
> > >
> > > /...../
> > >
> > > da = gtk_drawing_area_new ();
> > > gtk_widget_set_size_request (da, width,height);
> > > gtk_fixed_put(GTK_FIXED(fixed),da,50,50);
> > > g_signal_connect(da, "expose-event",G_CALLBACK (on_expose_event),
> > > NULL);
> > >
> > > /...../
> > >
> > > cairo_surface_destroy(image);
> > >
> > >   return 0;
> > > }
> > >
> > > /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
> > >
> > > Thanks in Advance.
> > >
> > > Regards,
> > > Chandra Shekhar Sengupta
> > >
> > >
> > > _______________________________________________
> > > cairo mailing list
> > > cairo at cairographics.org
> > > http://lists.cairographics.org/mailman/listinfo/cairo
> > >
> >
> >
>
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