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<div class="sect1" title="Converting Applications to gdk-pixbuf">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id576634"></a>Converting Applications to <span class="application">gdk-pixbuf</span>
</h2></div></div></div>
<p>
This sections describes the actual changes you need to make in
an <span class="application">Imlib</span> program to make it use <span class="application">gdk-pixbuf</span> instead.
</p>
<div class="sect2" title="Image loading and creation">
<div class="titlepage"><div><div><h3 class="title">
<a name="id576663"></a>Image loading and creation</h3></div></div></div>
<p>
The <span class="application">gdk-pixbuf</span> library can load image files synchronously
(i.e. with a single function call), create images from RGB
data in memory, and as a convenience, it can also create
images from inline XPM data.
</p>
<p>
To load an image file in a single function call, simply use
<code class="function">gdk_pixbuf_new_from_file()</code>. Note that
this will make the program block until the whole file has
been read. This function effectively replaces
<code class="function">gdk_imlib_load_image()</code>.
</p>
<p>
If you have RGB data in memory, you can use
<code class="function">gdk_pixbuf_new_from_data()</code> to create a
pixbuf out of it; this is a replacement for
<code class="function">gdk_imlib_create_image_from_data()</code>.
<span class="application">gdk-pixbuf</span> does not copy the image data; it is up to you
to define the ownership policy by providing a destroy
notification function that will be called when the image
data needs to be freed. The function you provide can then
free the data or do something else, as appropriate.
</p>
<p>
As a convenience, you can use the
<code class="function">gdk_pixbuf_new_from_xpm_data()</code> function
to create a pixbuf out of inline XPM data that was compiled
into your C program. This is a replacement for
<code class="function">gdk_imlib_create_image_from_xpm_data()</code>.
</p>
<p>
After you have created a pixbuf, you can manipulate it in
any way you please and then finally call
<code class="function">g_object_unref()</code> when you are done
with it. This can be thought of as a replacement for
<code class="function">gdk_imlib_destroy_image()</code> but with much
cleaner semantics.
</p>
</div>
<div class="sect2" title="Rendering Images">
<div class="titlepage"><div><div><h3 class="title">
<a name="id576852"></a>Rendering Images</h3></div></div></div>
<p>
Applications that use <span class="application">Imlib</span> must first call
<code class="function">gdk_imlib_render()</code> to render the whole
image data onto a pixmap that <span class="application">Imlib</span> creates. Then they
must copy that pixmap's data into the final destination for
the image.
</p>
<p>
In contrast, <span class="application">gdk-pixbuf</span> provides convenience functions to
render arbitrary rectangular regions of an image onto a
drawable that your application provides. You can use
<code class="function">gdk_draw_pixbuf()</code> to do this; having
your application provide the destination drawable and
specify an arbitrary region means your application has
complete control over the way images are rendered.
</p>
<p>
As a convenience, <span class="application">gdk-pixbuf</span> also provides the
<code class="function">gdk_pixbuf_render_pixmap_and_mask()</code>
function; this will create new pixmap and mask drawables for
a whole pixbuf and render the image data onto them. Only
trivially simple applications should find a use for this
function, since usually you want finer control of how things
are rendered.
</p>
</div>
<div class="sect2" title="Scaling Images">
<div class="titlepage"><div><div><h3 class="title">
<a name="id576921"></a>Scaling Images</h3></div></div></div>
<p>
<span class="application">Imlib</span> lets you render scaled image data at the time you
call <code class="function">gdk_imlib_render()</code>. Again, this
unfortunately scales and renders the whole image onto a new
pixmap.
</p>
<p>
<span class="application">gdk-pixbuf</span> provides a number of functions that do scaling
of arbitrary regions of a source pixbuf onto a destination
one. These functions can also perform compositing
operations against the data in the destination pixbuf or
against a solid color or a colored checkerboard.
<sup>[<a name="id576954" href="#ftn.id576954" class="footnote">1</a>]</sup>
</p>
<p>
Very simple applications may find it sufficient to use
<code class="function">gdk_pixbuf_scale_simple()</code> or
<code class="function">gdk_pixbuf_composite_color_simple()</code>.
These functions scale the whole source image at a time and
create a new pixbuf with the result.
</p>
<p>
More sophisticated applications will need to use
<code class="function">gdk_pixbuf_scale()</code>,
<code class="function">gdk_pixbuf_composite()</code>, or
<code class="function">gdk_pixbuf_composite_color()</code> instead.
These functions let you scale and composite an arbitrary
region of the source pixbuf onto a destination pixbuf that
you provide.
</p>
</div>
<div class="sect2" title="Getting Image Data from a Drawable">
<div class="titlepage"><div><div><h3 class="title">
<a name="id577013"></a>Getting Image Data from a Drawable</h3></div></div></div>
<p>
<span class="application">Imlib</span> lets you create an image by fetching a drawable's
contents from the X server and converting those into RGB
data. This is done with the
<code class="function">gdk_imlib_create_image_from_drawable()</code>
function.
</p>
<p>
<span class="application">gdk-pixbuf</span> provides the
<code class="function">gdk_pixbuf_get_from_drawable()</code> function
instead. It lets you specify a destination pixbuf instead
of always creating a new one for you.
</p>
</div>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote">
<p><sup>[<a name="ftn.id576954" href="#id576954" class="para">1</a>] </sup>
You can use a colored checkerboard as the background for
compositing when you want to provide a visual indication
that the image has partially opaque areas. This is
normally used in image editing and viewing programs.
</p>
<p>
Compositing against a single solid color is actually a
special case of a checkerboard; it simply uses checks of
the same color.
</p>
</div>
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