Re: Some questions I\

[Olexiy Avramchenko <olexiy irtech cn ua>]

Freddie Unpenstein wrote:

> There's a few things that've been bugging me of late, and I was just wondering if anyone here could shed any 
> light on any of these points:
>
> 1) An easy way to determine what image format a file is encoded in, if in fact it is an image at all.  (And 
> possibly obtain some basic image stats)  At present I'm loading the entire image, just to see if it is an 
> image, and throw it away again.  There are other ways, but although slow, this is the easiest.  The closest I 
> can think of without resorting to running external programs, or fiddling around with image libraries, is to 
> use the progressive Image Loader.  As I understand it, it will emit a signal as soon as it has basic image 
> configuration information.  I don't recall from the documentation, however, how to determine the format of 
> the image being loaded?
>  
I've attached small sample that shows how to do this with 
GdkPixbufLoader. You can learn more at:
http://developer.gnome.org/doc/API/2.0/gdk-pixbuf/GdkPixbufLoader.html
http://developer.gnome.org/doc/API/2.0/gdk-pixbuf/gdk-pixbuf-Module-Interface.html#GdkPixbufFormat

PS: As for question 4) - when you get "size-prepared" signal, the image 
dimensions are known, so you can use gtk_widget_size_request to resize 
your widgets.

   Olexiy

#include <stdio.h>
#include <stdlib.h>
#include <gdk/gdk.h>
#include <gdk-pixbuf/gdk-pixbuf.h>


static void get_format(GdkPixbufLoader *loader)
{
gchar           **ss;
GdkPixbufFormat *format;

        format = gdk_pixbuf_loader_get_format(loader);
        g_return_if_fail(format!=NULL);

        printf("%s\n", gdk_pixbuf_format_get_name(format));

        ss = gdk_pixbuf_format_get_mime_types(format);
        for (; *ss; ss++)
                printf("\tMIME type: '%s'\n", *ss);

        exit(0);
}

int main(int argc, char **argv)
{
char            buffer[1024];
size_t          size;
FILE            *f;
GdkPixbufLoader *loader;

        if (argc < 2) {
                fprintf(stderr, "Usage: ff <filename>\n");
                return -1;
        }

        gdk_init(&argc, &argv);

        loader = gdk_pixbuf_loader_new();
        g_signal_connect(loader, "size-prepared", G_CALLBACK(get_format), 0);

        f = fopen(argv[1], "r");
        if ( !f ) {
                fprintf(stderr, "Can't open \"%s\"\n", argv[1]);
                return -1;
        }

        while ( (size=fread(buffer, 1, sizeof(buffer), f)) > 0 )
                gdk_pixbuf_loader_write(loader, buffer, size, NULL);

        fclose(f);

        return -1;
}

ff: ff.c
        gcc -Wall `pkg-config --cflags --libs gdk-pixbuf-2.0 gdk-2.0` $< -o $@