path: root/docs/reference/gdk-pixbuf/tmpl/gdk-pixbuf.sgml

<!-- ##### SECTION Title ##### -->
The GdkPixbuf Structure

<!-- ##### SECTION Short_Description ##### -->
Information that describes an image.

<!-- ##### SECTION Long_Description ##### -->

  <para>
    The <structname>GdkPixbuf</structname> structure contains
    information that describes an image in memory.
  </para>

  <section id="image-data">
    <title>Image Data</title>

    <para>
      Image data in a pixbuf is stored in memory in uncompressed,
      packed format.  Rows in the image are stored top to bottom, and
      in each row pixels are stored from left to right.  There may be
      padding at the end of a row.  The "rowstride" value of a pixbuf,
      as returned by gdk_pixbuf_get_rowstride(), indicates the number
      of bytes between rows.
    </para>

    <example id="put-pixel">
      <title>put_pixel(<!-- -->) example</title>

      <para>
	The following code illustrates a simple put_pixel(<!-- -->)
	function for RGB pixbufs with 8 bits per channel with an alpha
	channel.  It is not included in the gdk-pixbuf library for
	performance reasons; rather than making several function calls
	for each pixel, your own code can take shortcuts.
      </para>

      <programlisting>
static void
put_pixel (GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha)
{
  int width, height, rowstride, n_channels;
  guchar *pixels, *p;

  n_channels = gdk_pixbuf_get_n_channels (pixbuf);

  g_assert (gdk_pixbuf_get_colorspace (pixbuf) == GDK_COLORSPACE_RGB);
  g_assert (gdk_pixbuf_get_bits_per_sample (pixbuf) == 8);
  g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
  g_assert (n_channels == 4);

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

  g_assert (x &gt;= 0 &amp;&amp; x &lt; width);
  g_assert (y &gt;= 0 &amp;&amp; y &lt; height);

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

  p = pixels + y * rowstride + x * n_channels;
  p[0] = red;
  p[1] = green;
  p[2] = blue;
  p[3] = alpha;
}
      </programlisting>

      <para>
	This function will not work for pixbufs with images that are
	other than 8 bits per sample or channel, but it will work for
	most of the pixbufs that GTK+ uses.
      </para>
    </example>

    <note>
      <para>
	If you are doing memcpy() of raw pixbuf data, note that the
	last row in the pixbuf may not be as wide as the full
	rowstride, but rather just as wide as the pixel data needs to
	be.  That is, it is unsafe to do <literal>memcpy (dest,
	pixels, rowstride * height)</literal> to copy a whole pixbuf.
	Use gdk_pixbuf_copy() instead, or compute the width in bytes
	of the last row as <literal>width * ((n_channels *
	bits_per_sample + 7) / 8)</literal>.
      </para>
    </note>
  </section>

<!-- ##### SECTION See_Also ##### -->
  <para>
  </para>

<!-- ##### SECTION Stability_Level ##### -->


<!-- ##### ENUM GdkPixbufError ##### -->
<para>
An error code in the #GDK_PIXBUF_ERROR domain. Many &gdk-pixbuf;
operations can cause errors in this domain, or in the #G_FILE_ERROR
domain.
</para>

@GDK_PIXBUF_ERROR_CORRUPT_IMAGE: An image file was broken somehow.
@GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY: Not enough memory.
@GDK_PIXBUF_ERROR_BAD_OPTION: A bad option was passed to a pixbuf save module.
@GDK_PIXBUF_ERROR_UNKNOWN_TYPE: Unknown image type.
@GDK_PIXBUF_ERROR_UNSUPPORTED_OPERATION: Don't know how to perform the
given operation on the type of image at hand.
@GDK_PIXBUF_ERROR_FAILED: Generic failure code, something went wrong.

<!-- ##### MACRO GDK_PIXBUF_ERROR ##### -->
<para>
Error domain used for pixbuf operations. Indicates that the error code
will be in the #GdkPixbufError enumeration. See #GError for
information on error domains and error codes.
</para>



<!-- ##### ENUM GdkColorspace ##### -->
  <para>
    This enumeration defines the color spaces that are supported by
    the &gdk-pixbuf; library.  Currently only RGB is supported.
  </para>

@GDK_COLORSPACE_RGB: Indicates a red/green/blue additive color space.

<!-- ##### ENUM GdkPixbufAlphaMode ##### -->
  <para>
    These values can be passed to
    gdk_pixbuf_render_to_drawable_alpha() to control how the alpha
    channel of an image should be handled.  This function can create a
    bilevel clipping mask (black and white) and use it while painting
    the image.  In the future, when the X Window System gets an alpha
    channel extension, it will be possible to do full alpha
    compositing onto arbitrary drawables.  For now both cases fall
    back to a bilevel clipping mask.
  </para>

@GDK_PIXBUF_ALPHA_BILEVEL: A bilevel clipping mask (black and white)
will be created and used to draw the image.  Pixels below 0.5 opacity
will be considered fully transparent, and all others will be
considered fully opaque.
@GDK_PIXBUF_ALPHA_FULL: For now falls back to #GDK_PIXBUF_ALPHA_BILEVEL.
In the future it will do full alpha compositing.

<!-- ##### STRUCT GdkPixbuf ##### -->
  <para>
    This is the main structure in the &gdk-pixbuf; library.  It is
    used to represent images.  It contains information about the
    image's pixel data, its color space, bits per sample, width and
    height, and the rowstride (the number of bytes between the start of
    one row and the start of the next). 
  </para>


<!-- ##### ARG GdkPixbuf:bits-per-sample ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:colorspace ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:has-alpha ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:height ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:n-channels ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:pixels ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:rowstride ##### -->
<para>

</para>

<!-- ##### ARG GdkPixbuf:width ##### -->
<para>

</para>

<!-- ##### FUNCTION gdk_pixbuf_get_colorspace ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_n_channels ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_has_alpha ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_bits_per_sample ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_pixels ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_width ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_height ##### -->
<para>

</para>

@pixbuf: 
@Returns: 


<!-- ##### FUNCTION gdk_pixbuf_get_rowstride ##### -->
<para>

</para>

@pixbuf: 
@Returns: <!--
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<!-- ##### FUNCTION gdk_pixbuf_get_option ##### -->
<para>

</para>

@pixbuf: 
@key: 
@Returns: 


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