Question

当我调整GtkWindow的大小时，我希望GtkImage也可以调整大小，同时保持与以前相同的宽高比。关于如何使用GTK3

进行设置，我找不到任何好的例子

这是我到目前为止所尝试的：

#include <gtk/gtk.h>
#include <gdk-pixbuf/gdk-pixbuf.h>

GtkAllocation *allocation = g_new0 (GtkAllocation, 1); 

gboolean resize_image(GtkWidget *widget, GdkEvent *event, GtkWidget *window) {
    GdkPixbuf *pixbuf = gtk_image_get_pixbuf(GTK_IMAGE(widget));
    if (pixbuf == NULL) {
        g_printerr("Failed to resize image\n");
        return 1;
    }
    gtk_widget_get_allocation(GTK_WIDGET(widget), allocation);
    pixbuf = gdk_pixbuf_scale_simple(pixbuf, widget->allocation.width, widget->allocation.height, GDK_INTERP_BILINEAR);
    gtk_image_set_from_pixbuf(GTK_IMAGE(widget), pixbuf);
    return FALSE;
}

int main(int argc, char **argv) {
    GtkWidget *window = NULL;
    GtkWidget *image = NULL;
    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    image = gtk_image_new_from_file("image.jpg");
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(image, "draw", G_CALLBACK(resize_image), (gpointer)window);
    gtk_container_add(GTK_CONTAINER(window), image);
    gtk_widget_show_all(GTK_WIDGET(window));
    gtk_main();
    return 0;
}

此代码应该只是将Pixbuf的大小调整为父级的大小，但它不起作用，我得到这些错误：

GdkPixbuf-CRITICAL **：gdk_pixbuf_get_width：断言'GDK_IS_PIXBUF   （pixbuf）'失败

GLib-GObject-CRITICAL **：g_object_unref：断言'G_IS_OBJECT   （对象）'失败

即使这段代码有效，我也无法保持相同的宽高比，如何实现这一目标？

先谢谢

Answer 1

嗯，这样做的一个技巧是在图像和窗口之间使用GtkLayout。另外，请使用draw信号，而不是使用size-allocate信号。

我们将加载一个GdkPixbuf并将其用作缩放的参考，否则质量会因累积'调整大小'而恶化。

一个简单的方法是：

#include <gtk/gtk.h>
#include <gdk-pixbuf/gdk-pixbuf.h>

struct _resize_widgets {
   GtkWidget *image;
   GdkPixbuf *pixbuf;
};

typedef struct _resize_widgets ResizeWidgets;

gboolean resize_image(GtkWidget *widget, GdkRectangle *allocation, gpointer user_data) {
   int x,y,w,h;
   GdkPixbuf *pxbscaled;
   GtkWidget *image = (GtkWidget *) ((ResizeWidgets *) user_data)->image; 
   GdkPixbuf *pixbuf= (GdkPixbuf *) ((ResizeWidgets *) user_data)->pixbuf; 

   x = 0;
   y = 0;

   h = allocation->height;
   w = (gdk_pixbuf_get_width(pixbuf) * h) / gdk_pixbuf_get_height(pixbuf);

   pxbscaled = gdk_pixbuf_scale_simple(pixbuf, w, h, GDK_INTERP_BILINEAR);

   if (w < allocation->width) {
      x = (allocation->width - w) / 2;
      gtk_layout_move(GTK_LAYOUT(widget), image, x, y);
   }

   gtk_image_set_from_pixbuf(GTK_IMAGE(image), pxbscaled);

   g_object_unref (pxbscaled);

   return FALSE;
}

int main(int argc, char **argv) {
   GtkWidget *window = NULL;
   GtkWidget *image = NULL;
   GtkWidget *container = NULL;
   GdkPixbuf *pixbuf = NULL;
   ResizeWidgets *widgets;

   gtk_init(&argc, &argv);

   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
   container = gtk_layout_new(NULL, NULL);
   image = gtk_image_new();

   pixbuf = gdk_pixbuf_new_from_file ("image.png", NULL);
   if (pixbuf == NULL) {
      g_printerr("Failed to resize image\n");
      return 1;
   }

   widgets = g_new0(ResizeWidgets, 1);
   widgets->image = image;
   widgets->pixbuf = pixbuf;

   gtk_container_add(GTK_CONTAINER(window), container);
   gtk_layout_put(GTK_LAYOUT(container), image, 0, 0);

   gtk_widget_set_size_request (GTK_WIDGET(window), 20, 20);

   g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
   g_signal_connect(container, "size-allocate", G_CALLBACK(resize_image), widgets);

   gtk_widget_show_all(GTK_WIDGET(window));

   gtk_main();

   g_object_unref (pixbuf);
   g_free(widgets);

   return 0;
}

编译gcc -o main main.c pkg-config --cflags --libs gtk + -3.0`

这将保持纵横比。如果不需要，那么resize_image回调处理程序将是：

gboolean resize_image(GtkWidget *widget, GdkRectangle *allocation, gpointer user_data) {
   int x,y,w,h;
   GdkPixbuf *pxbscaled;
   GtkWidget *image = (GtkWidget *) ((ResizeWidgets *) user_data)->image; 
   GdkPixbuf *pixbuf= (GdkPixbuf *) ((ResizeWidgets *) user_data)->pixbuf; 

   pxbscaled = gdk_pixbuf_scale_simple(pixbuf, allocation->width, allocation->height, GDK_INTERP_BILINEAR);

   gtk_image_set_from_pixbuf(GTK_IMAGE(image), pxbscaled);

   g_object_unref (pxbscaled);

   return FALSE;
}

这是一个简单的黑客攻击，显然还有其他选择，例如用于绘制的cairo或只是检查更完整的Eye of Gnome (eog)实现。

GTK3：在保持纵横比的同时调整图像大小

1 个答案: