GTK+ Forums

gtkguan · Posted: Sat Sep 06, 2008 7:37 pm Post subject: A problem about zoom a image.

How do I zoom a image in? What is the exhaustive steps?
In my program, I use gdk_pixbuf_new_from_file() and gtk_image_new_from_pixbuf() functions to display the image. Then get the new pixbuf that modified the width and the height by gdk_pixbuf_scale_simple() .
But when I run this program, I find that it expend the memory each zooming the image (including zoom in and zoom out).
I know my program has a lot of faults. I want the concrete steps that zooming a image.
Thank you!

dreblen · Posted: Sat Sep 06, 2008 11:13 pm Post subject:

I don't really understand what your problem is (is memory not being freed?), but here's an example of gdk_pixbuf_scale_simple:

Code: (C)

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#include <gtk/gtk.h>

typedef struct _ImData
{
GtkImage *im;
GdkPixbuf *disp;
GdkPixbuf *full;
GtkRange *scale;
} ImData;

void file_set_cb(GtkFileChooser *fc, ImData *id)
{
GError *err;
gchar *filename;

err = NULL;

/* get a filename, if the action was canceled, filename will be == NULL */
filename = gtk_file_chooser_get_filename(fc);
if(filename == NULL)
return;

/* reset the hscale and make sure that it's sensitive */
gtk_range_set_value(id->scale, 1);
if(GTK_WIDGET_SENSITIVE(id->scale) == FALSE)
gtk_widget_set_sensitive(GTK_WIDGET(id->scale), TRUE);

/* if our full and disp != NULL, then free them since they're old */
if(id->full != NULL)
g_free(id->full);
if(id->disp != NULL)
g_free(id->disp);

/* get our fullsized pixbuf */
id->full = gdk_pixbuf_new_from_file(filename, &err);
if(err != NULL)
{
g_warning(err->message);
g_error_free(err);
return;
}

/* right now, disp is the same as the fullsized pixbuf */
id->disp = id->full;

/* update the image */
gtk_image_set_from_pixbuf(id->im, id->disp);
}

void value_changed_cb(GtkRange *range, ImData *id)
{
gdouble scalef;
gint w, h;

/* if the pixbuf hasn't been initialized yet */
if(id->full == NULL)
return;

/* the scale factor is == the value of the hscale */
scalef = gtk_range_get_value(range);

/* get the width and height ... */
w = gdk_pixbuf_get_width(id->full);
h = gdk_pixbuf_get_height(id->full);

/* ...now scale the width and height by the scale factor */
w *= scalef;
h *= scalef;

/* free our old disp pixbuf */
g_free(id->disp);
/* now disp is == full scaled by scalef */
id->disp = gdk_pixbuf_scale_simple(id->full, w, h, GDK_INTERP_BILINEAR);
/* update the image */
gtk_image_set_from_pixbuf(id->im, id->disp);
}

int main(int argc, char **argv)
{
GtkWidget *win;
GtkWidget *vbox;
GtkWidget *button;
GtkWidget *hscale;
GtkWidget *swin;
GtkWidget *im;

ImData *id;

id = g_slice_new(ImData);
id->disp = id->full = NULL;

gtk_init(&argc, &argv);

win = gtk_window_new(GTK_WINDOW_TOPLEVEL);
g_signal_connect(win, "delete-event", G_CALLBACK(gtk_main_quit), NULL);

vbox = gtk_vbox_new(FALSE, 2);
gtk_container_add(GTK_CONTAINER(win), vbox);
gtk_widget_show(vbox);

im = gtk_image_new();
id->im = GTK_IMAGE(im);

button = gtk_file_chooser_button_new("Select file", GTK_FILE_CHOOSER_ACTION_OPEN);
g_signal_connect(button, "file-set", G_CALLBACK(file_set_cb), (gpointer)id);
gtk_box_pack_start(GTK_BOX(vbox), button, FALSE, FALSE, 0);
gtk_widget_show(button);

hscale = gtk_hscale_new_with_range(0.1, 2, 0.1);
g_signal_connect(hscale, "value-changed", G_CALLBACK(value_changed_cb), (gpointer)id);
gtk_range_set_value(GTK_RANGE(hscale), 1);
gtk_box_pack_start(GTK_BOX(vbox), hscale, FALSE, FALSE, 0);
gtk_widget_show(hscale);
gtk_widget_set_sensitive(hscale, FALSE);
id->scale = GTK_RANGE(hscale);

swin = gtk_scrolled_window_new(NULL, NULL);
gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(swin), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
gtk_box_pack_start(GTK_BOX(vbox), swin, TRUE, TRUE, 0);
gtk_widget_show(swin);

gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(swin), im);
gtk_widget_show(im);

gtk_widget_show(win);

gtk_main();

return 0;
}

gtkguan · Posted: Tue Sep 09, 2008 10:51 pm Post subject:

thanks!
But I think there is a defect in the upper example.(I run this program in MS windows xp. )
I opend a 1MB bitmap file and maximize the window. And every time I move the slider back and forth, the memory space occupied by this program is increasing all the time. At last
the value reaches to 330,000KB.I do not explain this phenomenon.
But when I minimize the window, the value declines to 3,120KB.

dreblen · Posted: Tue Sep 09, 2008 11:04 pm Post subject:

thanks for pointing that out, I'll be looking into it as soon as I can...

dreblen · Posted: Wed Sep 10, 2008 12:40 am Post subject:

okay, I've fixed the memory problems.
all that's changed is that i'm using gdk_pixbuf_copy instead of direct assignment,
and g_object_unref instead of g_free

Code: (C)

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#include <gtk/gtk.h>

typedef struct _ImData
{
GtkImage *im;
GdkPixbuf *disp;
GdkPixbuf *full;
GtkRange *scale;
} ImData;

void file_set_cb(GtkFileChooser *fc, ImData *id)
{
GError *err;
gchar *filename;

err = NULL;

/* get a filename, if the action was canceled, filename will be == NULL */
filename = gtk_file_chooser_get_filename(fc);
if(filename == NULL)
return;

/* reset the hscale and make sure that it's sensitive */
gtk_range_set_value(id->scale, 1);
if(GTK_WIDGET_SENSITIVE(id->scale) == FALSE)
gtk_widget_set_sensitive(GTK_WIDGET(id->scale), TRUE);

/* if our full and disp != NULL, then free them since they're old */
if(id->full != NULL)
g_free(id->full);
if(id->disp != NULL)
g_free(id->disp);

/* get our fullsized pixbuf */
id->full = gdk_pixbuf_new_from_file(filename, &err);
if(err != NULL)
{
g_warning(err->message);
g_error_free(err);
return;
}

/* right now, disp is the same as the fullsized pixbuf */
id->disp = gdk_pixbuf_copy(id->full);

/* update the image */
gtk_image_set_from_pixbuf(id->im, id->disp);
}

void value_changed_cb(GtkRange *range, ImData *id)
{
gdouble scalef;
gint w, h;

/* if the pixbuf hasn't been initialized yet */
if(id->full == NULL)
return;

/* the scale factor is == the value of the hscale */
scalef = gtk_range_get_value(range);

/* get the width and height ... */
w = gdk_pixbuf_get_width(id->full);
h = gdk_pixbuf_get_height(id->full);

/* ...now scale the width and height by the scale factor */
w *= scalef;
h *= scalef;

/* free our old disp pixbuf */
g_object_unref(id->disp);
/* now disp is == full scaled by scalef */
id->disp = gdk_pixbuf_scale_simple(id->full, w, h, GDK_INTERP_BILINEAR);
/* update the image */
gtk_image_set_from_pixbuf(id->im, id->disp);
}

int main(int argc, char **argv)
{
GtkWidget *win;
GtkWidget *vbox;
GtkWidget *button;
GtkWidget *hscale;
GtkWidget *swin;
GtkWidget *im;

ImData *id;

id = g_slice_new(ImData);
id->disp = id->full = NULL;

gtk_init(&argc, &argv);

win = gtk_window_new(GTK_WINDOW_TOPLEVEL);
g_signal_connect(win, "delete-event", G_CALLBACK(gtk_main_quit), NULL);

vbox = gtk_vbox_new(FALSE, 2);
gtk_container_add(GTK_CONTAINER(win), vbox);
gtk_widget_show(vbox);

im = gtk_image_new();
id->im = GTK_IMAGE(im);

button = gtk_file_chooser_button_new("Select file", GTK_FILE_CHOOSER_ACTION_OPEN);
g_signal_connect(button, "file-set", G_CALLBACK(file_set_cb), (gpointer)id);
gtk_box_pack_start(GTK_BOX(vbox), button, FALSE, FALSE, 0);
gtk_widget_show(button);

hscale = gtk_hscale_new_with_range(0.1, 2, 0.1);
g_signal_connect(hscale, "value-changed", G_CALLBACK(value_changed_cb), (gpointer)id);
gtk_range_set_value(GTK_RANGE(hscale), 1);
gtk_box_pack_start(GTK_BOX(vbox), hscale, FALSE, FALSE, 0);
gtk_widget_show(hscale);
gtk_widget_set_sensitive(hscale, FALSE);
id->scale = GTK_RANGE(hscale);

swin = gtk_scrolled_window_new(NULL, NULL);
gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(swin), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);
gtk_box_pack_start(GTK_BOX(vbox), swin, TRUE, TRUE, 0);
gtk_widget_show(swin);

gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(swin), im);
gtk_widget_show(im);

gtk_widget_show(win);

gtk_main();

return 0;
}

ramesh · GTK+ Guru Joined: 16 Nov 2006 Posts: 270 Location: INDIA

dreblen · Posted: Thu Sep 11, 2008 9:16 pm Post subject:

can you post your steps to reproduce?
I'm not getting a double free on my ubuntu system or my vista system.
are you using the latest version of the example?

virgoptrex@yahoo.com · Familiar Face Joined: 03 Feb 2010 Posts: 21

tadeboro · Posted: Mon Feb 08, 2010 7:44 pm Post subject:

Hi.

Those segfaults are probably caused by lines 30 and 32. g_free() on those lines should be replaced by g_object_unref().

Tadej

virgoptrex@yahoo.com · Familiar Face Joined: 03 Feb 2010 Posts: 21

tadeboro · Posted: Mon Feb 08, 2010 9:09 pm Post subject:

Hi.

What steps do you need to take to make this application segfault?

Tadej

virgoptrex@yahoo.com · Familiar Face Joined: 03 Feb 2010 Posts: 21