Fitting image to GtkImage size

tnetennba · **Joined:** Thu Dec 29, 2011 11:45 am **Posts:** 5

I use gtk_image_set_from_file to load a picture into GtkImage, but it resizes the control so that the whole image is shown. I would like it to be scaled down to the current size of GtkImage widget. How to fit the picture in GtkImage?

asdfgh2091 · **Joined:** Fri Sep 04, 2009 6:53 am **Posts:** 61

First you have to load you picture in an GdkPixBuf by using gdk_pixbuf_new_from_file, then you have to scale it by using gdk_pixbuf_scale or gdk_pixbuf_scale_simple. Something like this should work in gtk+2.0:

Code:

#define WIDTH 500
#define HEIGHT 500

#include <gtk/gtk.h>

int main(int argc, char **argv)
{
    gtk_init(&argc,&argv);
    GtkWidget *window=gtk_window_new(GTK_WINDOW_TOPLEVEL);
    g_signal_connect(G_OBJECT(window),"destroy",G_CALLBACK(gtk_main_quit),NULL);

    GtkWidget *image=gtk_image_new();
    gtk_container_add(GTK_CONTAINER(window),image);
    gtk_widget_set_size_request(image,WIDTH,HEIGHT);

    GdkPixbuf *original=gdk_pixbuf_new_from_file("test.jpg",NULL);
// error handling is missing
    GdkPixbuf *scaled=
        gdk_pixbuf_scale_simple(original,WIDTH,HEIGHT,GDK_INTERP_HYPER);
    gtk_image_set_from_pixbuf(GTK_IMAGE(image),scaled);

    gtk_widget_show_all(window);
    gtk_main();
    return 0;
}

tnetennba · **Joined:** Thu Dec 29, 2011 11:45 am **Posts:** 5

Seems fine but the thing is, that my GtkImage has to fill one part of VBox which changes size whenever the window is resizes. Nevertheless, I haven't got fixed width and height, I would have to extract it somehow from GtkImage control size. How to do that?

asdfgh2091 · **Joined:** Fri Sep 04, 2009 6:53 am **Posts:** 61

It might be easier to draw your image in a drawing area by using cairo:

Code:

#include <gtk/gtk.h>

GdkPixbuf *scaled=NULL;
GdkPixbuf *original=NULL;

void on_size(GtkWidget *widget, GdkRectangle *allocation, gpointer data)
{
    static gint height_old=-1;
    static gint width_old=-1;
    if ((width_old==allocation->width) && (height_old==allocation->height))
    {
        return;
    }
    if (scaled)
    {
        g_object_unref(scaled); // not sure if this prevents memory overflow
    }
    scaled=gdk_pixbuf_scale_simple(original,
                                   allocation->width,allocation->height,  
                                   GDK_INTERP_HYPER);
    height_old=allocation->height;
    width_old=allocation->width;
}

gboolean on_expose(GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
    cairo_t *cr=gdk_cairo_create(gtk_widget_get_window(widget));
    gdk_cairo_set_source_pixbuf(cr,scaled,0,0);
    cairo_paint(cr);
    cairo_destroy(cr);
    return TRUE;
}

int main(int argc, char **argv)
{
    gtk_init(&argc,&argv);
    GtkWidget *window=gtk_window_new(GTK_WINDOW_TOPLEVEL);
    g_signal_connect(G_OBJECT(window),"destroy",G_CALLBACK(gtk_main_quit),NULL);

    GtkWidget *drawing_area=gtk_drawing_area_new();
    gtk_container_add(GTK_CONTAINER(window),drawing_area);
    gtk_widget_set_app_paintable(drawing_area,FALSE);

    original=gdk_pixbuf_new_from_file("test.jpg",NULL);

    g_signal_connect(G_OBJECT(drawing_area),"size-allocate",
                     G_CALLBACK(on_size),NULL);
    g_signal_connect(G_OBJECT(drawing_area),"expose-event",
                     G_CALLBACK(on_expose),NULL);

    gtk_widget_show_all(window);
    gtk_main();
    return 0;
}

tnetennba · **Joined:** Thu Dec 29, 2011 11:45 am **Posts:** 5

Okay, It doesn't seem to work, or, which is more likely, I am unable to place this code into my application. I need the image to be shown after selecting it from GtkIconView. I think I have already handled that - in function which is called when item-activated event (signal? I'm getting used to GTK...) occurs I retrieve the path of the file to be shown and I'd like to trigger image drawing (in GtkDrawingArea as you suggested) from there - when the file is selected.

Nevertheless, what I got in the output using your solution was

Code:

(App1.exe:932): Gtk-CRITICAL **: gtk_widget_set_app_paintable: assertion `GTK
_IS_WIDGET (widget)' failed

(App1.exe:932): GLib-GObject-WARNING **: invalid (NULL) pointer instance

(App1.exe:932): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion `G
_TYPE_CHECK_INSTANCE (instance)' failed

(App1.exe:932): GLib-GObject-WARNING **: invalid (NULL) pointer instance

(App1.exe:932): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion `G
_TYPE_CHECK_INSTANCE (instance)' failed

asdfgh2091 · **Joined:** Fri Sep 04, 2009 6:53 am **Posts:** 61

You have called gtk_widget_set_app_paintable() with the argument widget=NULL. You have forgotten to initialize widget=gtk_widget_drawing_area_new() or whatever you have called the drawing area..

tnetennba · **Joined:** Thu Dec 29, 2011 11:45 am **Posts:** 5

How to get GdkRectangle of GtkDrawingArea manually? Or else: I'd like to paint the picture after loading it from file (file name got with dialog in Button-Clicked event). By the way, can I put GtkDrawingArea in a scrolled window container?

GTK+ Forums

Fitting image to GtkImage size

Who is online