GTK+ Forums

kprasanna16 · Familiar Face Joined: 08 Dec 2006 Posts: 11

I want to genetate a GdkImage from a file .. (so that this GdkImage can be passed to gdk_draw_image())
I used following calls..

GtkImage *gtk_image = NULL;
GdkImage *gdk_image = NULL;
GdkBitmap *gdk_bitmap = NULL;

gtk_image_set_from_file (gtk_image, "1.jpg");
gtk_image_set_from_image (gtk_image, gdk_image, gdk_bitmap);
gdk_draw_image (pixmap, widget->style->white_gc, gdk_image,
0, 0, 60, 60, 100, 100);

but while running the appliction I'm getting following error..
Gtk-CRITICAL **: gtk_image_set_from_file: assertion `GTK_IS_IMAGE (image)' failed

can anyone tell what is the problem.

Micah Carrick · Posted: Wed Dec 20, 2006 6:42 pm Post subject:

You have to create the GtkImage first...

Code: (Plaintext)
1	gtk_image_new_from_file (gtk_image, "1.jpg");

As far as your two calls... why are you calling this? You've already set the image by filename.
gdk_draw_image. I'm assuming you're trying to draw the image onto a GdkPixmap you have defined elsewhere named "pixmap"?

Try this maybe... (just guessing here):

Code: (Plaintext)
1 2 3 4 5 6 7 8 9	GtkImage gtk_image = NULL; GdkImage gdk_image = NULL; gtk_image_new_from_file (gtk_image, "1.jpg"); gtk_image_get_image (gtk_image, &gdk_image, NULL); gdk_draw_image (pixmap, widget->style->white_gc, gdk_image, 0, 0, 60, 60, 100, 100);

kprasanna16 · Familiar Face Joined: 08 Dec 2006 Posts: 11

Micah Carrick · Posted: Thu Dec 21, 2006 8:51 am Post subject:

Okay... my bad. I just did that really quickly and didn't look closely at the return type. Furthermore, I believe gtk_image_new_from_file is loading a GTK_IMAGE_PIXBUF (GdkPixbuf). I haven't done muc with any of this... I'm just looking at the API-- I've never had to use much of the Gdk level image functions. But, could you use a GdkPixbuf instead? I can't really look into this thoroughly at the moment... but... it looks like you might be able to do something along the lines of:

Code: (Plaintext)
1 2 3 4 5 6	GdkPixbuf gdk_pixbuf = NULL; gdk_pixbuf = gdk_pixbuf_new_from_file ("1.jpg", NULL); / The NULL ignores errors */ gdk_draw_pixbuf (pixmap, widget->style->white_gc, gdk_image, 0, 0, 60, 60, 100, 100, GDK_RGB_DITHER_NONE, 0, 0);

If I may ask... what is this for? That is, what are you trying to achieve. I'm sure someone here could provide more help if we knew your overall objective.

PS.
The appropriate way to use the gtk_image_new_from_file function would have been:

Code: (Plaintext)
1 2	GtkWidget *gtk_image = NULL; gtk_image = gtk_image_new_from_file ("1.jpg");

and then you could pass it to function requiring a GtkImage by casting it:

Code: (Plaintext)
1	hypothetical_function (GTK_IMAGE (gtk_image), "foobar");

The idea here is that you can declare any widget which is derived from the base class of GtkWidget as a GtkWidget and then cast it into the type needed by the function.