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<div class="refentry" title="Image Surfaces">
<a name="cairo-Image-Surfaces"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
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<h2><span class="refentrytitle"><a name="cairo-Image-Surfaces.top_of_page"></a>Image Surfaces</span></h2>
<p>Image Surfaces — Rendering to memory buffers</p>
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<div class="refsynopsisdiv" title="Synopsis">
<a name="cairo-Image-Surfaces.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">#define <a class="link" href="cairo-Image-Surfaces.html#CAIRO-HAS-IMAGE-SURFACE:CAPS" title="CAIRO_HAS_IMAGE_SURFACE">CAIRO_HAS_IMAGE_SURFACE</a>
enum <a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t">cairo_format_t</a>;
<span class="returnvalue">int</span> <a class="link" href="cairo-Image-Surfaces.html#cairo-format-stride-for-width" title="cairo_format_stride_for_width ()">cairo_format_stride_for_width</a> (<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>);
<a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="returnvalue">cairo_surface_t</span></a> * <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-create" title="cairo_image_surface_create ()">cairo_image_surface_create</a> (<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>,
<em class="parameter"><code><span class="type">int</span> height</code></em>);
<a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="returnvalue">cairo_surface_t</span></a> * <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-create-for-data" title="cairo_image_surface_create_for_data ()">cairo_image_surface_create_for_data</a> (<em class="parameter"><code>unsigned <span class="type">char</span> *data</code></em>,
<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>,
<em class="parameter"><code><span class="type">int</span> height</code></em>,
<em class="parameter"><code><span class="type">int</span> stride</code></em>);
unsigned <span class="returnvalue">char</span> * <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-get-data" title="cairo_image_surface_get_data ()">cairo_image_surface_get_data</a> (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);
<a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="returnvalue">cairo_format_t</span></a> <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-get-format" title="cairo_image_surface_get_format ()">cairo_image_surface_get_format</a> (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);
<span class="returnvalue">int</span> <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-get-width" title="cairo_image_surface_get_width ()">cairo_image_surface_get_width</a> (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);
<span class="returnvalue">int</span> <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-get-height" title="cairo_image_surface_get_height ()">cairo_image_surface_get_height</a> (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);
<span class="returnvalue">int</span> <a class="link" href="cairo-Image-Surfaces.html#cairo-image-surface-get-stride" title="cairo_image_surface_get_stride ()">cairo_image_surface_get_stride</a> (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);
</pre>
</div>
<div class="refsect1" title="Description">
<a name="cairo-Image-Surfaces.description"></a><h2>Description</h2>
<p>
Image surfaces provide the ability to render to memory buffers
either allocated by cairo or by the calling code. The supported
image formats are those defined in <a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a>.
</p>
</div>
<div class="refsect1" title="Details">
<a name="cairo-Image-Surfaces.details"></a><h2>Details</h2>
<div class="refsect2" title="CAIRO_HAS_IMAGE_SURFACE">
<a name="CAIRO-HAS-IMAGE-SURFACE:CAPS"></a><h3>CAIRO_HAS_IMAGE_SURFACE</h3>
<pre class="programlisting">#define CAIRO_HAS_IMAGE_SURFACE 1
</pre>
<p>
Defined if the image surface backend is available.
The image surface backend is always built in.
This macro was added for completeness in cairo 1.8.
</p>
<p>
<em class="parameter"><code>Since</code></em>: 1.8
</p>
</div>
<hr>
<div class="refsect2" title="enum cairo_format_t">
<a name="cairo-format-t"></a><h3>enum cairo_format_t</h3>
<pre class="programlisting">typedef enum _cairo_format {
CAIRO_FORMAT_INVALID = -1,
CAIRO_FORMAT_ARGB32 = 0,
CAIRO_FORMAT_RGB24 = 1,
CAIRO_FORMAT_A8 = 2,
CAIRO_FORMAT_A1 = 3,
CAIRO_FORMAT_RGB16_565 = 4
} cairo_format_t;
</pre>
<p>
<a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> is used to identify the memory format of
image data.
</p>
<p>
New entries may be added in future versions.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><a name="CAIRO-FORMAT-INVALID:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_INVALID</code></span></p></td>
<td>no such format exists or is supported.
</td>
</tr>
<tr>
<td><p><a name="CAIRO-FORMAT-ARGB32:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_ARGB32</code></span></p></td>
<td>each pixel is a 32-bit quantity, with
alpha in the upper 8 bits, then red, then green, then blue.
The 32-bit quantities are stored native-endian. Pre-multiplied
alpha is used. (That is, 50% transparent red is 0x80800000,
not 0x80ff0000.)
</td>
</tr>
<tr>
<td><p><a name="CAIRO-FORMAT-RGB24:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_RGB24</code></span></p></td>
<td>each pixel is a 32-bit quantity, with
the upper 8 bits unused. Red, Green, and Blue are stored
in the remaining 24 bits in that order.
</td>
</tr>
<tr>
<td><p><a name="CAIRO-FORMAT-A8:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_A8</code></span></p></td>
<td>each pixel is a 8-bit quantity holding
an alpha value.
</td>
</tr>
<tr>
<td><p><a name="CAIRO-FORMAT-A1:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_A1</code></span></p></td>
<td>each pixel is a 1-bit quantity holding
an alpha value. Pixels are packed together into 32-bit
quantities. The ordering of the bits matches the
endianess of the platform. On a big-endian machine, the
first pixel is in the uppermost bit, on a little-endian
machine the first pixel is in the least-significant bit.
</td>
</tr>
<tr>
<td><p><a name="CAIRO-FORMAT-RGB16-565:CAPS"></a><span class="term"><code class="literal">CAIRO_FORMAT_RGB16_565</code></span></p></td>
<td>each pixel is a 16-bit quantity
with red in the upper 5 bits, then green in the middle
6 bits, and blue in the lower 5 bits.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" title="cairo_format_stride_for_width ()">
<a name="cairo-format-stride-for-width"></a><h3>cairo_format_stride_for_width ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> cairo_format_stride_for_width (<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>);</pre>
<p>
This function provides a stride value that will respect all
alignment requirements of the accelerated image-rendering code
within cairo. Typical usage will be of the form:
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
int stride;
unsigned char *data;
<a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t">cairo_surface_t</a> *surface;
stride = cairo_format_stride_for_width (format, width);
data = malloc (stride * height);
surface = cairo_image_surface_create_for_data (data, format,
width, height,
stride);
</pre></div>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>format</code></em> :</span></p></td>
<td>A <a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> value
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>width</code></em> :</span></p></td>
<td>The desired width of an image surface to be created.
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> the appropriate stride to use given the desired
format and width, or -1 if either the format is invalid or the width
too large.
</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 1.6</p>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_create ()">
<a name="cairo-image-surface-create"></a><h3>cairo_image_surface_create ()</h3>
<pre class="programlisting"><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="returnvalue">cairo_surface_t</span></a> * cairo_image_surface_create (<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>,
<em class="parameter"><code><span class="type">int</span> height</code></em>);</pre>
<p>
Creates an image surface of the specified format and
dimensions. Initially the surface contents are all
0. (Specifically, within each pixel, each color or alpha channel
belonging to format will be 0. The contents of bits within a pixel,
but not belonging to the given format are undefined).
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>format</code></em> :</span></p></td>
<td>format of pixels in the surface to create
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>width</code></em> :</span></p></td>
<td>width of the surface, in pixels
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>height</code></em> :</span></p></td>
<td>height of the surface, in pixels
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a pointer to the newly created surface. The caller
owns the surface and should call <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-destroy" title="cairo_surface_destroy ()"><code class="function">cairo_surface_destroy()</code></a> when done
with it.
This function always returns a valid pointer, but it will return a
pointer to a "nil" surface if an error such as out of memory
occurs. You can use <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-status" title="cairo_surface_status ()"><code class="function">cairo_surface_status()</code></a> to check for this.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_create_for_data ()">
<a name="cairo-image-surface-create-for-data"></a><h3>cairo_image_surface_create_for_data ()</h3>
<pre class="programlisting"><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="returnvalue">cairo_surface_t</span></a> * cairo_image_surface_create_for_data (<em class="parameter"><code>unsigned <span class="type">char</span> *data</code></em>,
<em class="parameter"><code><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="type">cairo_format_t</span></a> format</code></em>,
<em class="parameter"><code><span class="type">int</span> width</code></em>,
<em class="parameter"><code><span class="type">int</span> height</code></em>,
<em class="parameter"><code><span class="type">int</span> stride</code></em>);</pre>
<p>
Creates an image surface for the provided pixel data. The output
buffer must be kept around until the <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> is destroyed
or <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-finish" title="cairo_surface_finish ()"><code class="function">cairo_surface_finish()</code></a> is called on the surface. The initial
contents of <em class="parameter"><code>data</code></em> will be used as the initial image contents; you
must explicitly clear the buffer, using, for example,
<a class="link" href="cairo-Paths.html#cairo-rectangle" title="cairo_rectangle ()"><code class="function">cairo_rectangle()</code></a> and <a class="link" href="cairo-cairo-t.html#cairo-fill" title="cairo_fill ()"><code class="function">cairo_fill()</code></a> if you want it cleared.
</p>
<p>
Note that the stride may be larger than
width*bytes_per_pixel to provide proper alignment for each pixel
and row. This alignment is required to allow high-performance rendering
within cairo. The correct way to obtain a legal stride value is to
call <a class="link" href="cairo-Image-Surfaces.html#cairo-format-stride-for-width" title="cairo_format_stride_for_width ()"><code class="function">cairo_format_stride_for_width()</code></a> with the desired format and
maximum image width value, and then use the resulting stride value
to allocate the data and to create the image surface. See
<a class="link" href="cairo-Image-Surfaces.html#cairo-format-stride-for-width" title="cairo_format_stride_for_width ()"><code class="function">cairo_format_stride_for_width()</code></a> for example code.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>a pointer to a buffer supplied by the application in which
to write contents. This pointer must be suitably aligned for any
kind of variable, (for example, a pointer returned by malloc).
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>format</code></em> :</span></p></td>
<td>the format of pixels in the buffer
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>width</code></em> :</span></p></td>
<td>the width of the image to be stored in the buffer
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>height</code></em> :</span></p></td>
<td>the height of the image to be stored in the buffer
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>stride</code></em> :</span></p></td>
<td>the number of bytes between the start of rows in the
buffer as allocated. This value should always be computed by
<a class="link" href="cairo-Image-Surfaces.html#cairo-format-stride-for-width" title="cairo_format_stride_for_width ()"><code class="function">cairo_format_stride_for_width()</code></a> before allocating the data
buffer.
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a pointer to the newly created surface. The caller
owns the surface and should call <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-destroy" title="cairo_surface_destroy ()"><code class="function">cairo_surface_destroy()</code></a> when done
with it.
This function always returns a valid pointer, but it will return a
pointer to a "nil" surface in the case of an error such as out of
memory or an invalid stride value. In case of invalid stride value
the error status of the returned surface will be
<a class="link" href="cairo-Error-handling.html#CAIRO-STATUS-INVALID-STRIDE:CAPS"><code class="literal">CAIRO_STATUS_INVALID_STRIDE</code></a>. You can use
<a class="link" href="cairo-cairo-surface-t.html#cairo-surface-status" title="cairo_surface_status ()"><code class="function">cairo_surface_status()</code></a> to check for this.
See <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-set-user-data" title="cairo_surface_set_user_data ()"><code class="function">cairo_surface_set_user_data()</code></a> for a means of attaching a
destroy-notification fallback to the surface if necessary.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_get_data ()">
<a name="cairo-image-surface-get-data"></a><h3>cairo_image_surface_get_data ()</h3>
<pre class="programlisting">unsigned <span class="returnvalue">char</span> * cairo_image_surface_get_data (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);</pre>
<p>
Get a pointer to the data of the image surface, for direct
inspection or modification.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>surface</code></em> :</span></p></td>
<td>a <span class="type">cairo_image_surface_t</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a pointer to the image data of this surface or <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>
if <em class="parameter"><code>surface</code></em> is not an image surface, or if <a class="link" href="cairo-cairo-surface-t.html#cairo-surface-finish" title="cairo_surface_finish ()"><code class="function">cairo_surface_finish()</code></a>
has been called.
</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 1.2</p>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_get_format ()">
<a name="cairo-image-surface-get-format"></a><h3>cairo_image_surface_get_format ()</h3>
<pre class="programlisting"><a class="link" href="cairo-Image-Surfaces.html#cairo-format-t" title="enum cairo_format_t"><span class="returnvalue">cairo_format_t</span></a> cairo_image_surface_get_format (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);</pre>
<p>
Get the format of the surface.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>surface</code></em> :</span></p></td>
<td>a <span class="type">cairo_image_surface_t</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> the format of the surface
</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 1.2</p>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_get_width ()">
<a name="cairo-image-surface-get-width"></a><h3>cairo_image_surface_get_width ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> cairo_image_surface_get_width (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);</pre>
<p>
Get the width of the image surface in pixels.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>surface</code></em> :</span></p></td>
<td>a <span class="type">cairo_image_surface_t</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> the width of the surface in pixels.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_get_height ()">
<a name="cairo-image-surface-get-height"></a><h3>cairo_image_surface_get_height ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> cairo_image_surface_get_height (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);</pre>
<p>
Get the height of the image surface in pixels.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>surface</code></em> :</span></p></td>
<td>a <span class="type">cairo_image_surface_t</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> the height of the surface in pixels.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" title="cairo_image_surface_get_stride ()">
<a name="cairo-image-surface-get-stride"></a><h3>cairo_image_surface_get_stride ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> cairo_image_surface_get_stride (<em class="parameter"><code><a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a> *surface</code></em>);</pre>
<p>
Get the stride of the image surface in bytes
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>surface</code></em> :</span></p></td>
<td>a <span class="type">cairo_image_surface_t</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> the stride of the image surface in bytes (or 0 if
<em class="parameter"><code>surface</code></em> is not an image surface). The stride is the distance in
bytes from the beginning of one row of the image data to the
beginning of the next row.
</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 1.2</p>
</div>
</div>
<div class="refsect1" title="See Also">
<a name="cairo-Image-Surfaces.see-also"></a><h2>See Also</h2>
<a class="link" href="cairo-cairo-surface-t.html#cairo-surface-t" title="cairo_surface_t"><span class="type">cairo_surface_t</span></a>
</div>
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