Re: gdk-pixbuf: rotate?

[Michael Rothwell <rothwell holly-springs nc us>]

Libart seemed a little heavy, so I did this:

/* rotates 24-bit gdkpixbuf 180 degrees */
char *rotate_180(char *buf, int len)
{
        int     x,y,z;
        char    t;
        char    *out;
        int pixels;
        out=(char *)malloc(128+sizeof(char)*len);
        memset(out,0,128+sizeof(char)*len);
        pixels=len/3;
        printf("rotating %d bytes of image data\n",len);
        for (z=0; z<pixels; z++)
        {
                x=z*3;
                for(y=0;y<3;y++)
                {
                        out[x+y]=buf[len-x+y];
                };
        };
        printf("done\n");
        return out;
}

... I pass it the output of gdk_pixbuf_get_pixels(mypixmaparea) and then
wrap the output into a pixbuf with gdk_pixbuf_new_from_data().

... now, for MMX... 

oh wait, I'm not a masochist.

-M

josh wrote:
> Michael Rothwell wrote:
> > With gdkpixbuf, I can copy one pixbuf onto an area of another. Is there
> > a way to also rotate it? I need to do a 180-degree rotate before or
> > during (or even after) the overlay.
>
> You need to use the libart-lgpl functions (which I think underly
> GdkPixbuf) directly.  With libart you can perform general affine
> transformations including rotations.  To use this with GdkPixbuf you
> need to dump the pixbuf into a packed rgb.
>
> Here's a simple example which loads an image into a pixbuf, scales it by
> a factor of two, performs a rotation ccw by 30 degrees, and composes it
> onto a black (the g_new0 commands initializes our data to 0) background.
>
> There's no docs I know of except directly in the source for libart_lgpl,
> so have a look at the files in CVS, for example:
>
> http://cvs.gnome.org/lxr/source/libart_lgpl/art_affine.c
>
> josh
>
> /* libart_example.c
>  *
>  * Copyright (C) 2000 josh buhl <jbuhl users sourceforge net>
>  *
>  * This program is free software; you can redistribute it and/or
>  * modify it under the terms of the GNU General Public License as
>  * published by the Free Software Foundation; either version 2, or (at
>  * your option) any later version.
>  *
>  * This program is distributed in the hope that it will be useful, but
>  * WITHOUT ANY WARRANTY; without even the implied warranty of
>  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>  * General Public License for more details.
>  *
>  * You should have received a copy of the GNU General Public License
>  * along with this program (see the file COPYING); if not, write to
>  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
>  * Boston, MA 02111-1307, USA
>  *
>  * Some of this code is from `Wanda-the-Fish' applet code by George Lebl
>  * (C) 1998 The Free Software Foundation.
>  */
>
> #include <gtk/gtk.h>
> #include <gnome.h>
> #include <gdk-pixbuf/gdk-pixbuf.h>
>
> #include <libart_lgpl/art_alphagamma.h>
> #include <libart_lgpl/art_filterlevel.h>
> #include <libart_lgpl/art_pixbuf.h>
> #include <libart_lgpl/art_rgb_pixbuf_affine.h>
> #include <libart_lgpl/art_affine.h>
> #include <libart_lgpl/art_rgb.h>
> #include <libart_lgpl/art_rgb_affine.h>
> #include <libart_lgpl/art_rgb_rgba_affine.h>
>
> #define IMAGE_WIDTH      256
> #define IMAGE_HEIGHT     256
>
> GtkWidget *blah_window;
> GtkWidget *blah_darea;
>
> static void
> load_image(gchar *pixmap)
> {
>     GdkPixbuf *pixbuf;
>             int x, y, h, w;
>
>     pixbuf = gdk_pixbuf_new_from_file(pixmap);
>     if(pixbuf) {
>         double affine[6];
>         guchar *rgb;
>
>         gint width, height;
>
>         width = gdk_pixbuf_get_width (pixbuf);
>         height = gdk_pixbuf_get_height (pixbuf);
>
>         h=IMAGE_HEIGHT;
>         w=IMAGE_WIDTH;
>
>         affine[0] = 0.866*2.0; /* = 2*cos(30) */
>         affine[2] = 0.5*2.0; /* = 2*sin(30) */
>         affine[3] = 0.866*2.0; /* = 2*cos(30) */
>         affine[1] = -0.5*2.0; /* = -2*sin(30) */
>
>         affine[4] = 80; /* x translation */
>         affine[5] = 128; /* y translation */
>
>         rgb = g_new0(guchar,w*h*3);
>
>         if (gdk_pixbuf_get_has_alpha (pixbuf)) {
>             art_rgb_rgba_affine (rgb, 20, 20, w,h, w * 3,
>                                  gdk_pixbuf_get_pixels (pixbuf),
>                                  width, height,
>                                  gdk_pixbuf_get_rowstride (pixbuf),
>                                  affine,
>                                  ART_FILTER_NEAREST,
>                                  NULL);
>
>         } else {
>             art_rgb_affine (rgb,
>                             0, 0, w, h, w * 3,
>                             gdk_pixbuf_get_pixels (pixbuf),
>                             width, height,
>                             gdk_pixbuf_get_rowstride (pixbuf),
>                             affine,
>                             ART_FILTER_NEAREST,
>                             NULL);
>         }
>
>         gdk_draw_rgb_image(blah_darea->window,
>                            blah_window->style->fg_gc[GTK_STATE_NORMAL],
>                            0, 0, w, h, GDK_RGB_DITHER_NORMAL,
>                            rgb, w*3);
>
>         gdk_pixbuf_unref(pixbuf);
>         g_free(rgb);
>     }
>
> }
>
> static void destroy_cb(GtkWidget * widget, gpointer data)
> {
>         gtk_widget_destroy(widget);
>         gtk_main_quit();
>
>         return;
> }
>
> int main (int argc, char **argv)
> {
>     gchar *file;
>
>     gtk_init(&argc, &argv);
>
>     gdk_rgb_init();
>
>     gtk_widget_push_visual (gdk_rgb_get_visual ());
>     gtk_widget_push_colormap (gdk_rgb_get_cmap ());
>
>     blah_window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
>
>     blah_darea = gtk_drawing_area_new();
>     gtk_drawing_area_size (GTK_DRAWING_AREA (blah_darea), IMAGE_WIDTH,
> IMAGE_HEIGHT);
>     gtk_container_add(GTK_CONTAINER(blah_window),blah_darea);
>     gtk_widget_show_now(blah_darea);
>     gtk_widget_show_now(blah_window);
>
>     gtk_widget_pop_colormap ();
>     gtk_widget_pop_visual ();
>
>     file = gnome_unconditional_pixmap_file ("apple-red.png");
>
>     load_image(file);
>
>     gtk_signal_connect(GTK_OBJECT(blah_window), "destroy",
>                        GTK_SIGNAL_FUNC(destroy_cb), NULL);
>
>     gtk_main ();
>
>     return 0;
>
> }
>
> --
> "I'll rob that rich person and give his gold to some poor undeserving
> slob.  That will *prove* I'm Robin Hood."
>         -- Daffy Duck, "Robin Hood Daffy", [1958, Chuck Jones]
>
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