Re: pixbuf rotation

[Aron Rubin <aron rubin lmco com>]

On 2/3/2009 2:41 AM, Roei Azachi wrote:
> Aron, Thank you very much fr your replay.
> if it is possible, can you specify the function I need to use for each 
> step you mentioned?
> I don't have very much experience in cairo.
> Again, Thanks a lot,
> Roei
>
> Aron Rubin wrote:
> > Roei Azachi wrote:
> >    
> > > Hi,
> > > Is there a way to rotate a pixbuf not by a multiple of 90 degrees (using
> > > gdk_pixbuf_rotate_simple)?
> > > I would like to rotate it by 10 degrees...
> > >      
> >
> > create a cairo image
> > make a cairo context on that new image
> > set the transform to be the rotation you want
> > load your original image
> > set the cairo source to be that original image
> > cairo paint
> > get the image back out (or not depending on your case)
> >      
Assuming you want to rotate to an image and not on screen it would look 
something like the attached code. If you wanted to rotate the image for 
display you could cut out the intermediate image.

Aron

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <glib.h>
#include <gtk/gtk.h>
#include <gdk/gdkcairo.h>

gboolean drawing_expose( GtkWidget *da, GdkEventExpose *event,
			 cairo_surface_t *img ) {
  cairo_t *cr = gdk_cairo_create( da->window );
  cairo_rectangle( cr, event->area.x, event->area.y,
		   event->area.width, event->area.height );
  cairo_clip( cr );
  cairo_set_source_surface( cr, img, 0, 0 );
  cairo_paint( cr );
  cairo_destroy( cr );
  
  return( FALSE );
}


cairo_surface_t *load_and_rotate_png( const char *filename, double angle_rad ) {
  cairo_t *cr;
  cairo_surface_t *iimg, *oimg;
  
  iimg = cairo_image_surface_create_from_png( filename );
  oimg = cairo_image_surface_create( CAIRO_FORMAT_RGB24,
				     cairo_image_surface_get_width( iimg ),
				     cairo_image_surface_get_height( iimg ) );
  cr = cairo_create( oimg );
  cairo_rotate( cr, angle_rad );
  cairo_set_source_surface( cr, iimg, 0, 0 );
  cairo_paint( cr );
  cairo_destroy( cr );

  cairo_surface_destroy( iimg );
  
  return( oimg );
}


void quit( void *unused ) {
  gtk_exit( 0 );
}


#define DEGTORAD (M_PI/180.0)

int main( int argc, char *argv[] ) {
  GtkWidget *win, *vbox, *da;
  cairo_surface_t *img;
  
  gtk_init( &argc, &argv );
  
  win = gtk_window_new( GTK_WINDOW_TOPLEVEL );
  gtk_widget_set_name( win, "Cairo Test" );
  
  vbox = gtk_vbox_new( FALSE, 0 );
  gtk_container_add( GTK_CONTAINER(win), vbox );
  gtk_widget_show( vbox );
  
  g_signal_connect( win, "destroy", G_CALLBACK(quit), NULL );
  
  // Create the drawing area
  
  da = gtk_drawing_area_new();
  img = load_and_rotate_png( argc > 1 ? argv[1] : "height.png",
			     (argc > 2 ? atof( argv[2] ) : 10.0)*DEGTORAD );
  g_signal_connect( da, "expose-event", G_CALLBACK(drawing_expose), img );
  
  //gtk_drawing_area_size( GTK_DRAWING_AREA(pie), 512, 512);
  gtk_box_pack_start( GTK_BOX(vbox), da, TRUE, TRUE, 0 );
  gtk_widget_show( da );
  
  gtk_widget_show_all( win );
  
  gtk_main();
  
  exit( 0 );
}