GTK BMP viewer

//#include <config.h>
#include <glib/gi18n.h>
#include <gtk/gtk.h>
#include <stdint.h>

struct _sBmpHeader {
    char bm[2];
    uint32_t size;
    uint32_t reserve;
    uint32_t offset;
    uint32_t header_size;
    uint32_t width;
    uint32_t height;
    uint16_t planes;
    uint16_t bpp;
    uint32_t compression;
    uint32_t bitmap_size;
    uint32_t hres;
    uint32_t vres;
    uint32_t used;
    uint32_t important;
} __attribute__((__packed__));

typedef struct _sBmpHeader sBmpHeader;

static void on_open_image(GtkButton *button, gpointer user_data) {
    GtkWidget *image = GTK_WIDGET(user_data);
    GtkWidget *toplevel = gtk_widget_get_toplevel(image);
    GtkFileFilter *filter = gtk_file_filter_new();
    GtkWidget *dialog = gtk_file_chooser_dialog_new(
        _("Open image"), GTK_WINDOW(toplevel), GTK_FILE_CHOOSER_ACTION_OPEN,
        GTK_STOCK_OK, GTK_RESPONSE_ACCEPT, GTK_STOCK_CANCEL,
        GTK_RESPONSE_CANCEL, NULL);

    gtk_file_filter_add_pixbuf_formats(filter);
    gtk_file_chooser_add_filter(GTK_FILE_CHOOSER(dialog), filter);

    switch (gtk_dialog_run(GTK_DIALOG(dialog))) {
        case GTK_RESPONSE_ACCEPT: {
            gchar *filename =
                gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(dialog));
            // gtk_image_set_from_file (GTK_IMAGE (image), filename);

            /*
            GdkPixbuf *
gdk_pixbuf_new (GdkColorspace colorspace,
    gboolean has_alpha,
    int bits_per_sample,
    int width,
    int height);
*/

            FILE *pFile = NULL;

            if ((pFile = fopen(filename, "rb")) == NULL) {
                printf("File could not be opened!\n");
                return;
            }

            sBmpHeader header;
            fread(&header, 54, 1, pFile);

            GdkPixbuf *pBuf = gdk_pixbuf_new(GDK_COLORSPACE_RGB, 0, 8,
                                             header.width, header.height);

            guchar *pixels = gdk_pixbuf_get_pixels(pBuf);

            size_t offset = 0;

            uint8_t *row_buf = malloc(header.width * sizeof(uint8_t) * 3);

            while (!feof(pFile)) {
                size_t count = fread(row_buf, 1,
                                     header.width * sizeof(uint8_t) * 3, pFile);

                // bgr -> rgb
                for (uint8_t *it = row_buf; it - row_buf < header.width * 3;
                     it += 3) {
                    // swap
                    uint8_t tmp = it[0];
                    it[0] = it[2];
                    it[2] = tmp;
                }

                memcpy(pixels +
                           ((header.width * 3 * (header.height - 1)) - offset),
                       row_buf, count);

                offset += count;
            }

            free(row_buf);

            gtk_image_set_from_pixbuf(GTK_IMAGE(image), pBuf);

            break;
        }
        default:
            break;
    }
    gtk_widget_destroy(dialog);
}

static GtkWidget *create_window(void) {
    GtkWidget *window;
    GtkWidget *button;
    GtkWidget *image;
    GtkWidget *box;

    /* Set up the UI */
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW(window), "image-viewer-c");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
    button = gtk_button_new_with_label(_("Open image"));
    image = gtk_image_new();

    gtk_box_pack_start(GTK_BOX(box), image, TRUE, TRUE, 0);
    gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 0);

    gtk_container_add(GTK_CONTAINER(window), box);

    /* Connect signals */

    /* Show open dialog when opening a file */
    g_signal_connect(button, "clicked", G_CALLBACK(on_open_image), image);

    /* Exit when the window is closed */
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    return window;
}

int main(int argc, char *argv[]) {
    GtkWidget *window;

#ifdef ENABLE_NLS
    bindtextdomain(GETTEXT_PACKAGE, PACKAGE_LOCALE_DIR);
    bind_textdomain_codeset(GETTEXT_PACKAGE, "UTF-8");
    textdomain(GETTEXT_PACKAGE);
#endif

    gtk_init(&argc, &argv);

    window = create_window();
    gtk_widget_show_all(window);

    gtk_main();
    return 0;
}