typedef enum {
    ANGLE_0 = 0,
    ANGLE_90 = 90,
    ANGLE_180 = 180,
    ANGLE_270 = 270
} rotate_angle_t;

static GdkPixbuf *
pixbuf_rotate(GdkPixbuf *src, rotate_angle_t angle) {
    GdkPixbuf *dest;
    int has_alpha;
    int s_width, s_height, s_rowstride;
    int d_width, d_height, d_rowstride;
    guchar *s_pix;
    guchar *d_pix;
    guchar *sp;
    guchar *dp;
    int i, j, pix_width;

    if (!src) return NULL;

    if (angle == ANGLE_0)
        return gdk_pixbuf_copy(src);

    s_width = gdk_pixbuf_get_width(src);
    s_height = gdk_pixbuf_get_height(src);
    has_alpha = gdk_pixbuf_get_has_alpha(src);
    s_rowstride = gdk_pixbuf_get_rowstride(src);
    s_pix = gdk_pixbuf_get_pixels(src);

    switch (angle) {
        case ANGLE_90:
        case ANGLE_270:
            d_width = s_height;
            d_height = s_width;
            break;
        default:
        case ANGLE_0:/* Avoid compiler warnings... */
        case ANGLE_180:
            d_width = s_width;
            d_height = s_height;
            break;
    }

    dest = gdk_pixbuf_new(GDK_COLORSPACE_RGB, has_alpha, 8, d_width, d_height);
    d_rowstride = gdk_pixbuf_get_rowstride(dest);
    d_pix = gdk_pixbuf_get_pixels(dest);

    pix_width = (has_alpha ? 4 : 3);

    for (i = 0; i < s_height; i++) {
        sp = s_pix + (i * s_rowstride);
        for (j = 0; j < s_width; j++) {
            switch (angle) {
                case ANGLE_180:
                    dp = d_pix + ((d_height - i - 1) * d_rowstride) + ((d_width - j - 1) * pix_width);
                    break;
                case ANGLE_90:
                    dp = d_pix + (j * d_rowstride) + ((d_width - i - 1) * pix_width);
                    break;
                case ANGLE_270:
                    dp = d_pix + ((d_height - j - 1) * d_rowstride) + (i * pix_width);
                    break;
                default:
                case ANGLE_0:/* Avoid compiler warnings... */
                    dp = d_pix + (i * d_rowstride) + (j * pix_width);
                    break;
            }

            *(dp++) = *(sp++);    /* red */
            *(dp++) = *(sp++);    /* green */
            *(dp++) = *(sp++);    /* blue */
            if (has_alpha) *(dp) = *(sp++);    /* alpha */
        }
    }

    return dest;
}