/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */

/* eel-gdk-pixbuf-extensions.c: Routines to augment what's in gdk-pixbuf.

   Copyright (C) 2000 Eazel, Inc.

   The Mate Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The Mate Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the Mate Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   Boston, MA 02110-1301, USA.

   Authors: Darin Adler <darin@eazel.com>
            Ramiro Estrugo <ramiro@eazel.com>
*/

#include <config.h>
#include "eel-gdk-pixbuf-extensions.h"

#include "eel-debug.h"
#include "eel-gdk-extensions.h"
#include "eel-glib-extensions.h"
#include "eel-graphic-effects.h"
#include "eel-lib-self-check-functions.h"
#include "eel-string.h"
#include <gdk-pixbuf/gdk-pixbuf.h>
#include <gdk/gdkprivate.h>
#include <gdk/gdkx.h>
#include <gio/gio.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>

#define LOAD_BUFFER_SIZE 65536

const EelIRect eel_gdk_pixbuf_whole_pixbuf = { G_MININT, G_MININT, G_MAXINT, G_MAXINT };

struct EelPixbufLoadHandle
{
    GCancellable *cancellable;
    GInputStream *stream;
    EelPixbufLoadCallback callback;
    gpointer callback_data;
    GdkPixbufLoader *loader;
    guchar buffer[LOAD_BUFFER_SIZE];
};

GdkPixbuf *
eel_gdk_pixbuf_load (const char *uri)
{
    GdkPixbuf *pixbuf;
    GFile *file;
    GFileInputStream *stream;

    g_return_val_if_fail (uri != NULL, NULL);

    file = g_file_new_for_uri (uri);

    stream = g_file_read (file, NULL, NULL);

    g_object_unref (file);

    if (stream == NULL)
    {
        return NULL;
    }

    pixbuf = eel_gdk_pixbuf_load_from_stream (G_INPUT_STREAM (stream));

    g_object_unref (stream);

    return pixbuf;
}

GdkPixbuf *
eel_gdk_pixbuf_load_from_stream (GInputStream  *stream)
{
    return eel_gdk_pixbuf_load_from_stream_at_size (stream, -1);
}

static void
pixbuf_loader_size_prepared (GdkPixbufLoader *loader,
                             int              width,
                             int              height,
                             gpointer         desired_size_ptr)
{
    int size, desired_size;
    float scale;

    size = MAX (width, height);
    desired_size = GPOINTER_TO_INT (desired_size_ptr);

    if (size != desired_size)
    {
        scale = (float) desired_size / size;
        gdk_pixbuf_loader_set_size (loader,
                                    floor (scale * width + 0.5),
                                    floor (scale * height + 0.5));
    }
}

GdkPixbuf *
eel_gdk_pixbuf_load_from_stream_at_size (GInputStream  *stream,
        int            size)
{
    guchar buffer[LOAD_BUFFER_SIZE];
    gssize bytes_read;
    GdkPixbufLoader *loader;
    GdkPixbuf *pixbuf;
    gboolean got_eos;


    g_return_val_if_fail (stream != NULL, NULL);

    got_eos = FALSE;
    loader = gdk_pixbuf_loader_new ();

    if (size > 0)
    {
        g_signal_connect (loader, "size-prepared",
                          G_CALLBACK (pixbuf_loader_size_prepared),
                          GINT_TO_POINTER (size));
    }

    while (1)
    {
        bytes_read = g_input_stream_read (stream, buffer, sizeof (buffer),
                                          NULL, NULL);

        if (bytes_read < 0)
        {
            break;
        }
        if (bytes_read == 0)
        {
            got_eos = TRUE;
            break;
        }
        if (!gdk_pixbuf_loader_write (loader,
                                      buffer,
                                      bytes_read,
                                      NULL))
        {
            break;
        }
    }

    g_input_stream_close (stream, NULL, NULL);
    gdk_pixbuf_loader_close (loader, NULL);

    pixbuf = NULL;
    if (got_eos)
    {
        pixbuf = gdk_pixbuf_loader_get_pixbuf (loader);
        if (pixbuf != NULL)
        {
            g_object_ref (pixbuf);
        }
    }

    g_object_unref (loader);

    return pixbuf;
}

static void
free_pixbuf_load_handle (EelPixbufLoadHandle *handle)
{
    g_object_unref (handle->cancellable);
    if (handle->loader != NULL)
    {
        g_object_unref (handle->loader);
    }
    if (handle->stream)
    {
        g_input_stream_close_async (handle->stream, 0, NULL, NULL, NULL);
        g_object_unref (handle->stream);
    }
    g_free (handle);
}

static void
load_done (EelPixbufLoadHandle *handle, GError *error, gboolean get_pixbuf)
{
    GdkPixbuf *pixbuf;

    if (handle->loader != NULL)
    {
        gdk_pixbuf_loader_close (handle->loader, NULL);
    }

    pixbuf = get_pixbuf ? gdk_pixbuf_loader_get_pixbuf (handle->loader) : NULL;

    handle->callback (error, pixbuf, handle->callback_data);

    free_pixbuf_load_handle (handle);
}

static void
file_read_callback (GObject *source_object,
                    GAsyncResult *res,
                    gpointer user_data)
{
    EelPixbufLoadHandle *handle;
    gssize bytes_read;
    GError *error;

    handle = user_data;

    if (g_cancellable_is_cancelled (handle->cancellable))
    {
        free_pixbuf_load_handle (handle);
        return;
    }

    error = NULL;
    bytes_read = g_input_stream_read_finish  (G_INPUT_STREAM (source_object),
                 res, &error);

    if (bytes_read > 0)
    {
        if (!gdk_pixbuf_loader_write (handle->loader,
                                      handle->buffer,
                                      bytes_read,
                                      &error))
        {
            bytes_read = -1;
        }
        else
        {
            g_input_stream_read_async (handle->stream,
                                       handle->buffer,
                                       sizeof (handle->buffer),
                                       0,
                                       handle->cancellable,
                                       file_read_callback, handle);
            return;
        }
    }

    load_done (handle, error, bytes_read == 0);

    if (error != NULL)
    {
        g_error_free (error);
    }
}

static void
file_opened_callback (GObject *source_object,
                      GAsyncResult *res,
                      gpointer user_data)
{
    EelPixbufLoadHandle *handle;
    GFileInputStream *stream;
    GError *error;

    handle = user_data;

    if (g_cancellable_is_cancelled (handle->cancellable))
    {
        free_pixbuf_load_handle (handle);
        return;
    }

    error = NULL;
    stream = g_file_read_finish (G_FILE (source_object), res, &error);

    if (stream == NULL)
    {
        load_done (handle, error, FALSE);
        g_error_free (error);
        return;
    }

    handle->stream = G_INPUT_STREAM (stream);
    handle->loader = gdk_pixbuf_loader_new ();


    g_input_stream_read_async (handle->stream,
                               handle->buffer,
                               sizeof (handle->buffer),
                               0,
                               handle->cancellable,
                               file_read_callback, handle);
}

EelPixbufLoadHandle *
eel_gdk_pixbuf_load_async (const char *uri,
                           int priority,
                           EelPixbufLoadCallback callback,
                           gpointer callback_data)
{
    EelPixbufLoadHandle *handle;
    GFile *file;

    handle = g_new0 (EelPixbufLoadHandle, 1);
    handle->cancellable = g_cancellable_new ();
    handle->callback = callback;
    handle->callback_data = callback_data;

    file = g_file_new_for_uri (uri);

    g_file_read_async (file, priority, handle->cancellable,
                       file_opened_callback, handle);

    return handle;
}

void
eel_cancel_gdk_pixbuf_load (EelPixbufLoadHandle *handle)
{
    if (handle == NULL)
    {
        return;
    }

    g_cancellable_cancel (handle->cancellable);
}

/* return the average value of each component */
guint32
eel_gdk_pixbuf_average_value (GdkPixbuf *pixbuf)
{
    guint64 a_total, r_total, g_total, b_total;
    guint row, column;
    int row_stride;
    const guchar *pixels, *p;
    int r, g, b, a;
    guint64 dividend;
    guint width, height;

    width = gdk_pixbuf_get_width (pixbuf);
    height = gdk_pixbuf_get_height (pixbuf);
    row_stride = gdk_pixbuf_get_rowstride (pixbuf);
    pixels = gdk_pixbuf_get_pixels (pixbuf);

    /* iterate through the pixbuf, counting up each component */
    a_total = 0;
    r_total = 0;
    g_total = 0;
    b_total = 0;

    if (gdk_pixbuf_get_has_alpha (pixbuf))
    {
        for (row = 0; row < height; row++)
        {
            p = pixels + (row * row_stride);
            for (column = 0; column < width; column++)
            {
                r = *p++;
                g = *p++;
                b = *p++;
                a = *p++;

                a_total += a;
                r_total += r * a;
                g_total += g * a;
                b_total += b * a;
            }
        }
        dividend = height * width * 0xFF;
        a_total *= 0xFF;
    }
    else
    {
        for (row = 0; row < height; row++)
        {
            p = pixels + (row * row_stride);
            for (column = 0; column < width; column++)
            {
                r = *p++;
                g = *p++;
                b = *p++;

                r_total += r;
                g_total += g;
                b_total += b;
            }
        }
        dividend = height * width;
        a_total = dividend * 0xFF;
    }

    return ((a_total + dividend / 2) / dividend) << 24
           | ((r_total + dividend / 2) / dividend) << 16
           | ((g_total + dividend / 2) / dividend) << 8
           | ((b_total + dividend / 2) / dividend);
}

double
eel_gdk_scale_to_fit_factor (int width, int height,
                             int max_width, int max_height,
                             int *scaled_width, int *scaled_height)
{
    double scale_factor;

    scale_factor = MIN (max_width  / (double) width, max_height / (double) height);

    *scaled_width  = floor (width * scale_factor + .5);
    *scaled_height = floor (height * scale_factor + .5);

    return scale_factor;
}

/* Returns a scaled copy of pixbuf, preserving aspect ratio. The copy will
 * be scaled as large as possible without exceeding the specified width and height.
 */
GdkPixbuf *
eel_gdk_pixbuf_scale_to_fit (GdkPixbuf *pixbuf, int max_width, int max_height)
{
    int scaled_width;
    int scaled_height;

    eel_gdk_scale_to_fit_factor (gdk_pixbuf_get_width(pixbuf), gdk_pixbuf_get_height(pixbuf),
                                 max_width, max_height,
                                 &scaled_width, &scaled_height);

    return gdk_pixbuf_scale_simple (pixbuf, scaled_width, scaled_height, GDK_INTERP_BILINEAR);
}

/* Returns a copy of pixbuf scaled down, preserving aspect ratio, to fit
 * within the specified width and height. If it already fits, a copy of
 * the original, without scaling, is returned.
 */
GdkPixbuf *
eel_gdk_pixbuf_scale_down_to_fit (GdkPixbuf *pixbuf, int max_width, int max_height)
{
    int scaled_width;
    int scaled_height;

    double scale_factor;

    scale_factor = eel_gdk_scale_to_fit_factor (gdk_pixbuf_get_width(pixbuf), gdk_pixbuf_get_height(pixbuf),
                   max_width, max_height,
                   &scaled_width, &scaled_height);

    if (scale_factor >= 1.0)
    {
        return gdk_pixbuf_copy (pixbuf);
    }
    else
    {
        return eel_gdk_pixbuf_scale_down (pixbuf, scaled_width, scaled_height);
    }
}

double
eel_gdk_scale_to_min_factor (int width, int height,
                             int min_width, int min_height,
                             int *scaled_width, int *scaled_height)
{
    double scale_factor;

    scale_factor = MAX (min_width / (double) width, min_height / (double) height);

    *scaled_width  = floor (width * scale_factor + .5);
    *scaled_height = floor (height * scale_factor + .5);

    return scale_factor;
}

/* Returns a scaled copy of pixbuf, preserving aspect ratio. The copy will
 * be scaled as small as possible without going under the specified width and height.
 */
GdkPixbuf *
eel_gdk_pixbuf_scale_to_min (GdkPixbuf *pixbuf, int min_width, int min_height)
{
    int scaled_width;
    int scaled_height;

    eel_gdk_scale_to_min_factor (gdk_pixbuf_get_width(pixbuf), gdk_pixbuf_get_height(pixbuf),
                                 min_width, min_height,
                                 &scaled_width, &scaled_height);

    return gdk_pixbuf_scale_simple (pixbuf, scaled_width, scaled_height, GDK_INTERP_BILINEAR);
}

/**
 * eel_gdk_pixbuf_is_valid:
 * @pixbuf: A GdkPixbuf
 *
 * Return value: A boolean indicating whether the given pixbuf is valid.
 *
 * A pixbuf is valid if:
 *
 *   1. It is non NULL
 *   2. It is has non NULL pixel data.
 *   3. It has width and height greater than 0.
 */
gboolean
eel_gdk_pixbuf_is_valid (const GdkPixbuf *pixbuf)
{
    return ((pixbuf != NULL)
            && (gdk_pixbuf_get_pixels (pixbuf) != NULL)
            && (gdk_pixbuf_get_width (pixbuf) > 0)
            && (gdk_pixbuf_get_height (pixbuf) > 0));
}

/**
 * eel_gdk_pixbuf_get_dimensions:
 * @pixbuf: A GdkPixbuf
 *
 * Return value: The dimensions of the pixbuf as a EelDimensions.
 *
 * This function is useful in code that uses libart rect
 * intersection routines.
 */
EelDimensions
eel_gdk_pixbuf_get_dimensions (const GdkPixbuf *pixbuf)
{
    EelDimensions dimensions;

    g_return_val_if_fail (eel_gdk_pixbuf_is_valid (pixbuf), eel_dimensions_empty);

    dimensions.width = gdk_pixbuf_get_width (pixbuf);
    dimensions.height = gdk_pixbuf_get_height (pixbuf);

    return dimensions;
}

/**
 * eel_gdk_pixbuf_fill_rectangle_with_color:
 * @pixbuf: Target pixbuf to fill into.
 * @area: Rectangle to fill.
 * @color: The color to use.
 *
 * Fill the rectangle with the the given color.
 */
void
eel_gdk_pixbuf_fill_rectangle_with_color (GdkPixbuf *pixbuf,
        EelIRect area,
        guint32 color)
{
    EelIRect target;
    guchar red;
    guchar green;
    guchar blue;
    guchar alpha;
    guchar *pixels;
    gboolean has_alpha;
    guint pixel_offset;
    guint rowstride;
    guchar *row_offset;
    int x;
    int y;

    g_return_if_fail (eel_gdk_pixbuf_is_valid (pixbuf));

    target = eel_gdk_pixbuf_intersect (pixbuf, 0, 0, area);
    if (eel_irect_is_empty (&target))
    {
        return;
    }

    pixels = gdk_pixbuf_get_pixels (pixbuf);
    rowstride = gdk_pixbuf_get_rowstride (pixbuf);
    has_alpha = gdk_pixbuf_get_has_alpha (pixbuf);
    pixel_offset = has_alpha ? 4 : 3;
    red = EEL_RGBA_COLOR_GET_R (color);
    green = EEL_RGBA_COLOR_GET_G (color);
    blue = EEL_RGBA_COLOR_GET_B (color);
    alpha = EEL_RGBA_COLOR_GET_A (color);

    row_offset = pixels + target.y0 * rowstride;

    for (y = target.y0; y < target.y1; y++)
    {
        guchar *offset = row_offset + (target.x0 * pixel_offset);

        for (x = target.x0; x < target.x1; x++)
        {
            *(offset++) = red;
            *(offset++) = green;
            *(offset++) = blue;

            if (has_alpha)
            {
                *(offset++) = alpha;
            }

        }

        row_offset += rowstride;
    }
}

gboolean
eel_gdk_pixbuf_save_to_file (const GdkPixbuf *pixbuf,
                             const char *file_name)
{
    return gdk_pixbuf_save ((GdkPixbuf *) pixbuf,
                            file_name, "png", NULL, NULL);
}

void
eel_gdk_pixbuf_ref_if_not_null (GdkPixbuf *pixbuf_or_null)
{
    if (pixbuf_or_null != NULL)
    {
        g_object_ref (pixbuf_or_null);
    }
}

void
eel_gdk_pixbuf_unref_if_not_null (GdkPixbuf *pixbuf_or_null)
{
    if (pixbuf_or_null != NULL)
    {
        g_object_unref (pixbuf_or_null);
    }
}

void
eel_gdk_pixbuf_draw_to_drawable (const GdkPixbuf *pixbuf,
#if GTK_CHECK_VERSION (3, 0, 0)
                                 cairo_t  *cr,
#else
                                 GdkDrawable *drawable,
#endif
                                 int source_x,
                                 int source_y,
                                 EelIRect destination_area)
{
    EelDimensions dimensions;
    EelIRect target;
    EelIRect source;
    int target_width;
    int target_height;
    int source_width;
    int source_height;
#if !GTK_CHECK_VERSION (3, 0, 0)
    cairo_t *cr;
#endif

    g_return_if_fail (eel_gdk_pixbuf_is_valid (pixbuf));
#if GTK_CHECK_VERSION (3, 0, 0)
    g_return_if_fail (cr != NULL);
#else
    g_return_if_fail (drawable != NULL);
#endif
    g_return_if_fail (!eel_irect_is_empty (&destination_area));

    dimensions = eel_gdk_pixbuf_get_dimensions (pixbuf);

    g_return_if_fail (source_x >= 0);
    g_return_if_fail (source_y >= 0);
    g_return_if_fail (source_x < dimensions.width);
    g_return_if_fail (source_y < dimensions.height);

    /* Clip the destination area to the pixbuf dimensions; bail if no work */
    target = eel_gdk_pixbuf_intersect (pixbuf,
                                       destination_area.x0,
                                       destination_area.y0,
                                       destination_area);
    if (eel_irect_is_empty (&target))
    {
        return;
    }

    /* Assign the source area */
    source = eel_irect_assign (source_x,
                               source_y,
                               dimensions.width - source_x,
                               dimensions.height - source_y);

    /* Adjust the target width if the source area is smaller than the
     * source pixbuf dimensions */
    target_width = target.x1 - target.x0;
    target_height = target.y1 - target.y0;
    source_width = source.x1 - source.x0;
    source_height = source.y1 - source.y0;

    target.x1 = target.x0 + MIN (target_width, source_width);
    target.y1 = target.y0 + MIN (target_height, source_height);

#if !GTK_CHECK_VERSION (3, 0, 0)
	cr = gdk_cairo_create (drawable);
#endif
	gdk_cairo_set_source_pixbuf (cr, (GdkPixbuf *) pixbuf,
				     source.x0 - target.x0, source.y0 - target.y0);
	cairo_rectangle (cr, target.x0, target.y0, 
                     target.x1 - target.x0,
			 target.y1 - target.y0);
	cairo_fill (cr);
	cairo_destroy (cr);
}

/**
 * eel_gdk_pixbuf_draw_to_pixbuf:
 * @pixbuf: The source pixbuf to draw.
 * @destination_pixbuf: The destination pixbuf.
 * @source_x: The source pixbuf x coordiate to composite from.
 * @source_y: The source pixbuf y coordiate to composite from.
 * @destination_area: The destination area within the destination pixbuf.
 *                    This area will be clipped if invalid in any way.
 *
 * Copy one pixbuf onto another another..  This function has some advantages
 * over plain gdk_pixbuf_copy_area():
 *
 *   Composition paramters (source coordinate, destination area) are
 *   given in a way that is consistent with the rest of the extensions
 *   in this file.  That is, it matches the declaration of
 *   eel_gdk_pixbuf_draw_to_pixbuf_alpha() and
 *   eel_gdk_pixbuf_draw_to_drawable() very closely.
 *
 *   All values are clipped to make sure they are valid.
 *
 */
void
eel_gdk_pixbuf_draw_to_pixbuf (const GdkPixbuf *pixbuf,
                               GdkPixbuf *destination_pixbuf,
                               int source_x,
                               int source_y,
                               EelIRect destination_area)
{
    EelDimensions dimensions;
    EelIRect target;
    EelIRect source;
    int target_width;
    int target_height;
    int source_width;
    int source_height;

    g_return_if_fail (eel_gdk_pixbuf_is_valid (pixbuf));
    g_return_if_fail (eel_gdk_pixbuf_is_valid (destination_pixbuf));
    g_return_if_fail (!eel_irect_is_empty (&destination_area));

    dimensions = eel_gdk_pixbuf_get_dimensions (pixbuf);

    g_return_if_fail (source_x >= 0);
    g_return_if_fail (source_y >= 0);
    g_return_if_fail (source_x < dimensions.width);
    g_return_if_fail (source_y < dimensions.height);

    /* Clip the destination area to the pixbuf dimensions; bail if no work */
    target = eel_gdk_pixbuf_intersect (destination_pixbuf, 0, 0, destination_area);
    if (eel_irect_is_empty (&target))
    {
        return;
    }

    /* Assign the source area */
    source = eel_irect_assign (source_x,
                               source_y,
                               dimensions.width - source_x,
                               dimensions.height - source_y);

    /* Adjust the target width if the source area is smaller than the
     * source pixbuf dimensions */
    target_width = target.x1 - target.x0;
    target_height = target.y1 - target.y0;
    source_width = source.x1 - source.x0;
    source_height = source.y1 - source.y0;

    target.x1 = target.x0 + MIN (target_width, source_width);
    target.y1 = target.y0 + MIN (target_height, source_height);

    gdk_pixbuf_copy_area (pixbuf,
                          source.x0,
                          source.y0,
                          target.x1 - target.x0,
                          target.y1 - target.y0,
                          destination_pixbuf,
                          target.x0,
                          target.y0);
}

/**
 * eel_gdk_pixbuf_draw_to_pixbuf_alpha:
 * @pixbuf: The source pixbuf to draw.
 * @destination_pixbuf: The destination pixbuf.
 * @source_x: The source pixbuf x coordiate to composite from.
 * @source_y: The source pixbuf y coordiate to composite from.
 * @destination_area: The destination area within the destination pixbuf.
 *                    This area will be clipped if invalid in any way.
 * @opacity: The opacity of the drawn tiles where 0 <= opacity <= 255.
 * @interpolation_mode: The interpolation mode.  See <gdk-pixbuf.h>
 *
 * Composite one pixbuf over another.  This function has some advantages
 * over plain gdk_pixbuf_composite():
 *
 *   Composition paramters (source coordinate, destination area) are
 *   given in a way that is consistent with the rest of the extensions
 *   in this file.  That is, it matches the declaration of
 *   eel_gdk_pixbuf_draw_to_pixbuf() and
 *   eel_gdk_pixbuf_draw_to_drawable() very closely.
 *
 *   All values are clipped to make sure they are valid.
 *
 *   Workaround a limitation in gdk_pixbuf_composite() that does not allow
 *   the source (x,y) to be greater than (0,0)
 *
 */
void
eel_gdk_pixbuf_draw_to_pixbuf_alpha (const GdkPixbuf *pixbuf,
                                     GdkPixbuf *destination_pixbuf,
                                     int source_x,
                                     int source_y,
                                     EelIRect destination_area,
                                     int opacity,
                                     GdkInterpType interpolation_mode)
{
    EelDimensions dimensions;
    EelIRect target;
    EelIRect source;
    int target_width;
    int target_height;
    int source_width;
    int source_height;

    g_return_if_fail (eel_gdk_pixbuf_is_valid (pixbuf));
    g_return_if_fail (eel_gdk_pixbuf_is_valid (destination_pixbuf));
    g_return_if_fail (!eel_irect_is_empty (&destination_area));
    g_return_if_fail (opacity >= EEL_OPACITY_FULLY_TRANSPARENT);
    g_return_if_fail (opacity <= EEL_OPACITY_FULLY_OPAQUE);
    g_return_if_fail (interpolation_mode >= GDK_INTERP_NEAREST);
    g_return_if_fail (interpolation_mode <= GDK_INTERP_HYPER);

    dimensions = eel_gdk_pixbuf_get_dimensions (pixbuf);

    g_return_if_fail (source_x >= 0);
    g_return_if_fail (source_y >= 0);
    g_return_if_fail (source_x < dimensions.width);
    g_return_if_fail (source_y < dimensions.height);

    /* Clip the destination area to the pixbuf dimensions; bail if no work */
    target = eel_gdk_pixbuf_intersect (destination_pixbuf, 0, 0, destination_area);
    if (eel_irect_is_empty (&target))
    {
        return;
    }

    /* Assign the source area */
    source = eel_irect_assign (source_x,
                               source_y,
                               dimensions.width - source_x,
                               dimensions.height - source_y);

    /* Adjust the target width if the source area is smaller than the
     * source pixbuf dimensions */
    target_width = target.x1 - target.x0;
    target_height = target.y1 - target.y0;
    source_width = source.x1 - source.x0;
    source_height = source.y1 - source.y0;

    target.x1 = target.x0 + MIN (target_width, source_width);
    target.y1 = target.y0 + MIN (target_height, source_height);

    /* If the source point is not (0,0), then we need to create a sub pixbuf
     * with only the source area.  This is needed to work around a limitation
     * in gdk_pixbuf_composite() that requires the source area to be (0,0). */
    if (source.x0 != 0 || source.y0 != 0)
    {
        EelIRect area;
        int width;
        int height;

        width = dimensions.width - source.x0;
        height = dimensions.height - source.y0;

        area.x0 = source.x0;
        area.y0 = source.y0;
        area.x1 = area.x0 + width;
        area.y1 = area.y0 + height;

        pixbuf = eel_gdk_pixbuf_new_from_pixbuf_sub_area ((GdkPixbuf *) pixbuf, area);
    }
    else
    {
        g_object_ref (G_OBJECT (pixbuf));
    }

    gdk_pixbuf_composite (pixbuf,
                          destination_pixbuf,
                          target.x0,
                          target.y0,
                          target.x1 - target.x0,
                          target.y1 - target.y0,
                          target.x0,
                          target.y0,
                          1.0,
                          1.0,
                          interpolation_mode,
                          opacity);

    g_object_unref (G_OBJECT (pixbuf));
}

static void
pixbuf_destroy_callback (guchar  *pixels,
                         gpointer callback_data)
{
    g_assert (pixels != NULL);
    g_assert (callback_data != NULL);

    g_object_unref (callback_data);
}

/**
 * eel_gdk_pixbuf_new_from_pixbuf_sub_area:
 * @pixbuf: The source pixbuf.
 * @area: The area within the source pixbuf to use for the sub pixbuf.
 *        This area needs to be contained within the bounds of the
 *        source pixbuf, otherwise it will be clipped to that.
 *
 * Return value: A newly allocated pixbuf that shares the pixel data
 *               of the source pixbuf in order to represent a sub area.
 *
 * Create a pixbuf from a sub area of another pixbuf.  The resulting pixbuf
 * will share the pixel data of the source pixbuf.  Memory bookeeping is
 * all taken care for the caller.  All you need to do is g_object_unref()
 * the resulting pixbuf to properly free resources.
 */
GdkPixbuf *
eel_gdk_pixbuf_new_from_pixbuf_sub_area (GdkPixbuf *pixbuf,
        EelIRect area)
{
    GdkPixbuf *sub_pixbuf;
    EelIRect target;
    guchar *pixels;

    g_return_val_if_fail (eel_gdk_pixbuf_is_valid (pixbuf), NULL);
    g_return_val_if_fail (!eel_irect_is_empty (&area), NULL);

    /* Clip the pixbuf by the given area; bail if no work */
    target = eel_gdk_pixbuf_intersect (pixbuf, 0, 0, area);
    if (eel_irect_is_empty (&target))
    {
        return NULL;
    }

    /* Since we are going to be sharing the given pixbuf's data, we need
     * to ref it.  It will be unreffed in the destroy function above */
    g_object_ref (pixbuf);

    /* Compute the offset into the pixel data */
    pixels =
        gdk_pixbuf_get_pixels (pixbuf)
        + (target.y0 * gdk_pixbuf_get_rowstride (pixbuf))
        + (target.x0 * (gdk_pixbuf_get_has_alpha (pixbuf) ? 4 : 3));

    /* Make a pixbuf pretending its real estate is the sub area */
    sub_pixbuf = gdk_pixbuf_new_from_data (pixels,
                                           GDK_COLORSPACE_RGB,
                                           gdk_pixbuf_get_has_alpha (pixbuf),
                                           8,
                                           eel_irect_get_width (target),
                                           eel_irect_get_height (target),
                                           gdk_pixbuf_get_rowstride (pixbuf),
                                           pixbuf_destroy_callback,
                                           pixbuf);

    return sub_pixbuf;
}

/**
 * eel_gdk_pixbuf_new_from_existing_buffer:
 * @buffer: The existing buffer.
 * @buffer_rowstride: The existing buffer's rowstride.
 * @buffer_has_alpha: A boolean value indicating whether the buffer has alpha.
 * @area: The area within the existing buffer to use for the pixbuf.
 *        This area needs to be contained within the bounds of the
 *        buffer, otherwise memory will be trashed.
 *
 * Return value: A newly allocated pixbuf that uses the existing buffer
 *               for its pixel data.
 *
 * Create a pixbuf from an existing buffer.
 *
 * The resulting pixbuf is only valid for as long as &buffer is valid.  It is
 * up to the caller to make sure they both exist in the same scope.
 * Also, it is up to the caller to make sure that the given area is fully
 * contained in the buffer, otherwise memory trashing will happen.
 */
GdkPixbuf *
eel_gdk_pixbuf_new_from_existing_buffer (guchar *buffer,
        int buffer_rowstride,
        gboolean buffer_has_alpha,
        EelIRect area)
{
    GdkPixbuf *pixbuf;
    guchar *pixels;

    g_return_val_if_fail (buffer != NULL, NULL);
    g_return_val_if_fail (buffer_rowstride > 0, NULL);
    g_return_val_if_fail (!eel_irect_is_empty (&area), NULL);

    /* Compute the offset into the buffer */
    pixels =
        buffer
        + (area.y0 * buffer_rowstride)
        + (area.x0 * (buffer_has_alpha ? 4 : 3));

    pixbuf = gdk_pixbuf_new_from_data (pixels,
                                       GDK_COLORSPACE_RGB,
                                       buffer_has_alpha,
                                       8,
                                       eel_irect_get_width (area),
                                       eel_irect_get_height (area),
                                       buffer_rowstride,
                                       NULL,
                                       NULL);

    return pixbuf;
}

/**
 * eel_gdk_pixbuf_intersect:
 * @pixbuf: A GdkPixbuf.
 * @pixbuf_x: X coordinate of pixbuf.
 * @pixbuf_y: Y coordinate of pixbuf.
 * @rectangle: An EelIRect.
 *
 * Return value: The intersection of the pixbuf and the given rectangle.
 *
 */
EelIRect
eel_gdk_pixbuf_intersect (const GdkPixbuf *pixbuf,
                          int pixbuf_x,
                          int pixbuf_y,
                          EelIRect rectangle)
{
    EelIRect intersection;
    EelIRect bounds;
    EelDimensions dimensions;

    g_return_val_if_fail (eel_gdk_pixbuf_is_valid (pixbuf), eel_irect_empty);

    dimensions = eel_gdk_pixbuf_get_dimensions (pixbuf);
    bounds = eel_irect_assign_dimensions (pixbuf_x, pixbuf_y, dimensions);

    eel_irect_intersect (&intersection, &rectangle, &bounds);

    /* In theory, this is not needed because a rectangle is empty
     * regardless of how MUCH negative the dimensions are.
     * However, to make debugging and self checks simpler, we
     * consistenly return a standard empty rectangle.
     */
    if (eel_irect_is_empty (&intersection))
    {
        return eel_irect_empty;
    }

    return intersection;
}

GdkPixbuf *
eel_gdk_pixbuf_scale_down (GdkPixbuf *pixbuf,
                           int dest_width,
                           int dest_height)
{
    int source_width, source_height;
    int s_x1, s_y1, s_x2, s_y2;
    int s_xfrac, s_yfrac;
    int dx, dx_frac, dy, dy_frac;
    div_t ddx, ddy;
    int x, y;
    int r, g, b, a;
    int n_pixels;
    gboolean has_alpha;
    guchar *dest, *src, *xsrc, *src_pixels;
    GdkPixbuf *dest_pixbuf;
    int pixel_stride;
    int source_rowstride, dest_rowstride;

    if (dest_width == 0 || dest_height == 0)
    {
        return NULL;
    }

    source_width = gdk_pixbuf_get_width (pixbuf);
    source_height = gdk_pixbuf_get_height (pixbuf);

    g_assert (source_width >= dest_width);
    g_assert (source_height >= dest_height);

    ddx = div (source_width, dest_width);
    dx = ddx.quot;
    dx_frac = ddx.rem;

    ddy = div (source_height, dest_height);
    dy = ddy.quot;
    dy_frac = ddy.rem;

    has_alpha = gdk_pixbuf_get_has_alpha (pixbuf);
    source_rowstride = gdk_pixbuf_get_rowstride (pixbuf);
    src_pixels = gdk_pixbuf_get_pixels (pixbuf);

    dest_pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, has_alpha, 8,
                                  dest_width, dest_height);
    dest = gdk_pixbuf_get_pixels (dest_pixbuf);
    dest_rowstride = gdk_pixbuf_get_rowstride (dest_pixbuf);

    pixel_stride = (has_alpha)?4:3;

    s_y1 = 0;
    s_yfrac = -dest_height/2;
    while (s_y1 < source_height)
    {
        s_y2 = s_y1 + dy;
        s_yfrac += dy_frac;
        if (s_yfrac > 0)
        {
            s_y2++;
            s_yfrac -= dest_height;
        }

        s_x1 = 0;
        s_xfrac = -dest_width/2;
        while (s_x1 < source_width)
        {
            s_x2 = s_x1 + dx;
            s_xfrac += dx_frac;
            if (s_xfrac > 0)
            {
                s_x2++;
                s_xfrac -= dest_width;
            }

            /* Average block of [x1,x2[ x [y1,y2[ and store in dest */
            r = g = b = a = 0;
            n_pixels = 0;

            src = src_pixels + s_y1 * source_rowstride + s_x1 * pixel_stride;
            for (y = s_y1; y < s_y2; y++)
            {
                xsrc = src;
                if (has_alpha)
                {
                    for (x = 0; x < s_x2-s_x1; x++)
                    {
                        n_pixels++;

                        r += xsrc[3] * xsrc[0];
                        g += xsrc[3] * xsrc[1];
                        b += xsrc[3] * xsrc[2];
                        a += xsrc[3];
                        xsrc += 4;
                    }
                }
                else
                {
                    for (x = 0; x < s_x2-s_x1; x++)
                    {
                        n_pixels++;
                        r += *xsrc++;
                        g += *xsrc++;
                        b += *xsrc++;
                    }
                }
                src += source_rowstride;
            }

            if (has_alpha)
            {
                if (a != 0)
                {
                    *dest++ = r / a;
                    *dest++ = g / a;
                    *dest++ = b / a;
                    *dest++ = a / n_pixels;
                }
                else
                {
                    *dest++ = 0;
                    *dest++ = 0;
                    *dest++ = 0;
                    *dest++ = 0;
                }
            }
            else
            {
                *dest++ = r / n_pixels;
                *dest++ = g / n_pixels;
                *dest++ = b / n_pixels;
            }

            s_x1 = s_x2;
        }
        s_y1 = s_y2;
        dest += dest_rowstride - dest_width * pixel_stride;
    }

    return dest_pixbuf;
}

static guchar
eel_gdk_pixbuf_lighten_pixbuf_component (guchar cur_value,
        guint lighten_value)
{
    int new_value = cur_value;
    if (lighten_value > 0)
    {
        new_value += lighten_value + (new_value >> 3);
        if (new_value > 255)
        {
            new_value = 255;
        }
    }
    return (guchar) new_value;
}

static GdkPixbuf *
eel_gdk_pixbuf_lighten (GdkPixbuf* src,
                        guint lighten_value)
{
    GdkPixbuf *dest;
    int i, j;
    int width, height, has_alpha, src_row_stride, dst_row_stride;
    guchar *target_pixels, *original_pixels;
    guchar *pixsrc, *pixdest;

    g_assert (gdk_pixbuf_get_colorspace (src) == GDK_COLORSPACE_RGB);
    g_assert ((!gdk_pixbuf_get_has_alpha (src)
               && gdk_pixbuf_get_n_channels (src) == 3)
              || (gdk_pixbuf_get_has_alpha (src)
                  && gdk_pixbuf_get_n_channels (src) == 4));
    g_assert (gdk_pixbuf_get_bits_per_sample (src) == 8);

    dest = gdk_pixbuf_new (gdk_pixbuf_get_colorspace (src),
                           gdk_pixbuf_get_has_alpha (src),
                           gdk_pixbuf_get_bits_per_sample (src),
                           gdk_pixbuf_get_width (src),
                           gdk_pixbuf_get_height (src));

    has_alpha = gdk_pixbuf_get_has_alpha (src);
    width = gdk_pixbuf_get_width (src);
    height = gdk_pixbuf_get_height (src);
    dst_row_stride = gdk_pixbuf_get_rowstride (dest);
    src_row_stride = gdk_pixbuf_get_rowstride (src);
    target_pixels = gdk_pixbuf_get_pixels (dest);
    original_pixels = gdk_pixbuf_get_pixels (src);

    for (i = 0; i < height; i++)
    {
        pixdest = target_pixels + i * dst_row_stride;
        pixsrc = original_pixels + i * src_row_stride;
        for (j = 0; j < width; j++)
        {
            *pixdest++ = eel_gdk_pixbuf_lighten_pixbuf_component (*pixsrc++, lighten_value);
            *pixdest++ = eel_gdk_pixbuf_lighten_pixbuf_component (*pixsrc++, lighten_value);
            *pixdest++ = eel_gdk_pixbuf_lighten_pixbuf_component (*pixsrc++, lighten_value);
            if (has_alpha)
            {
                *pixdest++ = *pixsrc++;
            }
        }
    }
    return dest;
}

GdkPixbuf *
eel_gdk_pixbuf_render (GdkPixbuf *pixbuf,
                       guint render_mode,
                       guint saturation,
                       guint brightness,
                       guint lighten_value,
                       guint color)
{
    GdkPixbuf *temp_pixbuf, *old_pixbuf;

    if (render_mode == 1)
    {
        /* lighten icon */
        temp_pixbuf = eel_create_spotlight_pixbuf (pixbuf);
    }
    else if (render_mode == 2)
    {
        /* colorize icon */
        temp_pixbuf = eel_create_colorized_pixbuf (pixbuf,
                      EEL_RGBA_COLOR_GET_R (color),
                      EEL_RGBA_COLOR_GET_G (color),
                      EEL_RGBA_COLOR_GET_B (color));
    }
    else if (render_mode == 3)
    {
        /* monochromely colorize icon */
        old_pixbuf = eel_create_darkened_pixbuf (pixbuf, 0, 255);
        temp_pixbuf = eel_create_colorized_pixbuf (old_pixbuf,
                      EEL_RGBA_COLOR_GET_R (color),
                      EEL_RGBA_COLOR_GET_G (color),
                      EEL_RGBA_COLOR_GET_B (color));
        g_object_unref (old_pixbuf);
    }
    else
    {
        temp_pixbuf = NULL;
    }

    if (saturation < 255 || brightness < 255 || temp_pixbuf == NULL)   // temp_pixbuf == NULL just for safer code (return copy)
    {
        old_pixbuf = temp_pixbuf;
        temp_pixbuf = eel_create_darkened_pixbuf (temp_pixbuf ? temp_pixbuf : pixbuf, saturation, brightness);
        if (old_pixbuf)
        {
            g_object_unref (old_pixbuf);
        }
    }

    if (lighten_value > 0)
    {
        old_pixbuf = temp_pixbuf;
        temp_pixbuf = eel_gdk_pixbuf_lighten (temp_pixbuf ? temp_pixbuf : pixbuf, lighten_value);
        if (old_pixbuf)
        {
            g_object_unref (old_pixbuf);
        }
    }

    return temp_pixbuf;
}


#if !defined (EEL_OMIT_SELF_CHECK)

static char *
check_average_value (int width, int height, const char* fill)
{
    char c;
    guint r, g, b, a;
    gboolean alpha, gray;
    int gray_tweak;
    GdkPixbuf *pixbuf;
    int x, y, rowstride, n_channels;
    guchar *pixels;
    guint32 average;
    guchar v;

    r = g = b = a = 0;
    alpha = FALSE;
    gray = FALSE;
    gray_tweak = 0;
    if (sscanf (fill, " %x,%x,%x,%x %c", &r, &g, &b, &a, &c) == 4)
    {
        alpha = TRUE;
    }
    else if (sscanf (fill, " %x,%x,%x %c", &r, &g, &b, &c) == 3)
    {
    }
    else if (sscanf (fill, " gray%d %c", &gray_tweak, &c) == 1)
    {
        gray = TRUE;
    }
    else
    {
        return g_strdup ("bad fill string format");
    }

    pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, alpha, 8, width, height);

    pixels = gdk_pixbuf_get_pixels (pixbuf);
    rowstride = gdk_pixbuf_get_rowstride (pixbuf);
    n_channels = gdk_pixbuf_get_n_channels (pixbuf);

    if (!gray)
    {
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                pixels [y * rowstride + x * n_channels + 0] = r;
                pixels [y * rowstride + x * n_channels + 1] = g;
                pixels [y * rowstride + x * n_channels + 2] = b;
                if (alpha)
                {
                    pixels [y * rowstride + x * n_channels + 3] = a;
                }
            }
        }
    }
    else
    {
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                v = ((x + y) & 1) ? 0x80 : 0x7F;
                if (((x + y) & 0xFF) == 0)
                    v += gray_tweak;
                pixels [y * rowstride + x * n_channels + 0] = v;
                pixels [y * rowstride + x * n_channels + 1] = v;
                pixels [y * rowstride + x * n_channels + 2] = v;
            }
        }
        pixels [0] += gray_tweak;
        pixels [1] += gray_tweak;
        pixels [2] += gray_tweak;
    }

    average = eel_gdk_pixbuf_average_value (pixbuf);
    g_object_unref (pixbuf);

    return g_strdup_printf ("%02X,%02X,%02X,%02X",
                            (average >> 16) & 0xFF,
                            (average >> 8) & 0xFF,
                            average & 0xFF,
                            average >> 24);
}

void
eel_self_check_gdk_pixbuf_extensions (void)
{
    GdkPixbuf *pixbuf;
    EelIRect clip_area;

    pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, 100, 100);

    EEL_CHECK_BOOLEAN_RESULT (eel_gdk_pixbuf_is_valid (pixbuf), TRUE);
    EEL_CHECK_BOOLEAN_RESULT (eel_gdk_pixbuf_is_valid (NULL), FALSE);

    EEL_CHECK_DIMENSIONS_RESULT (eel_gdk_pixbuf_get_dimensions (pixbuf), 100, 100);

    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, eel_gdk_pixbuf_whole_pixbuf), 0, 0, 100, 100);

    clip_area = eel_irect_assign (0, 0, 0, 0);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 0, 0);

    clip_area = eel_irect_assign (0, 0, 0, 0);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 0, 0);

    clip_area = eel_irect_assign (0, 0, 100, 100);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 100, 100);

    clip_area = eel_irect_assign (-10, -10, 100, 100);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 90, 90);

    clip_area = eel_irect_assign (-10, -10, 110, 110);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 100, 100);

    clip_area = eel_irect_assign (0, 0, 99, 99);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 99, 99);

    clip_area = eel_irect_assign (0, 0, 1, 1);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 1, 1);

    clip_area = eel_irect_assign (-1, -1, 1, 1);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 0, 0);

    clip_area = eel_irect_assign (-1, -1, 2, 2);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 1, 1);

    clip_area = eel_irect_assign (100, 100, 1, 1);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 0, 0);

    clip_area = eel_irect_assign (101, 101, 1, 1);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 0, 0, 0, 0);

    clip_area = eel_irect_assign (80, 0, 100, 100);
    EEL_CHECK_RECTANGLE_RESULT (eel_gdk_pixbuf_intersect (pixbuf, 0, 0, clip_area), 80, 0, 100, 100);

    g_object_unref (pixbuf);

    /* No checks for empty pixbufs because GdkPixbuf doesn't seem to allow them. */
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "00,00,00"), "00,00,00,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "00,00,00,00"), "00,00,00,00");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "00,00,00,FF"), "00,00,00,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "01,01,01"), "01,01,01,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "FE,FE,FE"), "FE,FE,FE,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "FF,FF,FF"), "FF,FF,FF,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "FF,FF,FF,00"), "00,00,00,00");
    EEL_CHECK_STRING_RESULT (check_average_value (1, 1, "11,22,33"), "11,22,33,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "00,00,00"), "00,00,00,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "00,00,00,00"), "00,00,00,00");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "00,00,00,FF"), "00,00,00,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "01,01,01"), "01,01,01,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "FE,FE,FE"), "FE,FE,FE,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "FF,FF,FF"), "FF,FF,FF,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "FF,FF,FF,00"), "00,00,00,00");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "11,22,33"), "11,22,33,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "gray -1"), "7F,7F,7F,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "gray 0"), "80,80,80,FF");
    EEL_CHECK_STRING_RESULT (check_average_value (1000, 1000, "gray 1"), "80,80,80,FF");
}

#endif /* !EEL_OMIT_SELF_CHECK */

