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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd">
<html><head><title>QImageWriter Class Reference</title><style>h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm }
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</style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr /><td align="left" valign="top" width="32"><img align="left" border="0" height="32" src="images/rb-logo.png" width="32" /></td><td width="1">  </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="modules.html"><font color="#004faf">Modules</font></a></td></table><h1 align="center">QImageWriter Class Reference<br /><sup><sup>[<a href="qtgui.html">QtGui</a> module]</sup></sup></h1><p>The QImageWriter class provides a format independent interface
for writing images to files or other devices. <a href="#details">More...</a></p>
<h3>Types</h3><ul><li><div class="fn" />enum <b><a href="qimagewriter.html#ImageWriterError-enum">ImageWriterError</a></b> { UnknownError, DeviceError, UnsupportedFormatError }</li></ul><h3>Methods</h3><ul><li><div class="fn" /><b><a href="qimagewriter.html#QImageWriter">__init__</a></b> (<i>self</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#QImageWriter-2">__init__</a></b> (<i>self</i>, QIODevice <i>device</i>, QByteArray <i>format</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#QImageWriter-3">__init__</a></b> (<i>self</i>, QString <i>fileName</i>, QByteArray <i>format</i> = QByteArray())</li><li><div class="fn" />bool <b><a href="qimagewriter.html#canWrite">canWrite</a></b> (<i>self</i>)</li><li><div class="fn" />int <b><a href="qimagewriter.html#compression">compression</a></b> (<i>self</i>)</li><li><div class="fn" />QString <b><a href="qimagewriter.html#description">description</a></b> (<i>self</i>)</li><li><div class="fn" />QIODevice <b><a href="qimagewriter.html#device">device</a></b> (<i>self</i>)</li><li><div class="fn" />ImageWriterError <b><a href="qimagewriter.html#error">error</a></b> (<i>self</i>)</li><li><div class="fn" />QString <b><a href="qimagewriter.html#errorString">errorString</a></b> (<i>self</i>)</li><li><div class="fn" />QString <b><a href="qimagewriter.html#fileName">fileName</a></b> (<i>self</i>)</li><li><div class="fn" />QByteArray <b><a href="qimagewriter.html#format">format</a></b> (<i>self</i>)</li><li><div class="fn" />float <b><a href="qimagewriter.html#gamma">gamma</a></b> (<i>self</i>)</li><li><div class="fn" />int <b><a href="qimagewriter.html#quality">quality</a></b> (<i>self</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setCompression">setCompression</a></b> (<i>self</i>, int <i>compression</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setDescription">setDescription</a></b> (<i>self</i>, QString <i>description</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setDevice">setDevice</a></b> (<i>self</i>, QIODevice <i>device</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setFileName">setFileName</a></b> (<i>self</i>, QString <i>fileName</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setFormat">setFormat</a></b> (<i>self</i>, QByteArray <i>format</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setGamma">setGamma</a></b> (<i>self</i>, float <i>gamma</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setQuality">setQuality</a></b> (<i>self</i>, int <i>quality</i>)</li><li><div class="fn" /><b><a href="qimagewriter.html#setText">setText</a></b> (<i>self</i>, QString <i>key</i>, QString <i>text</i>)</li><li><div class="fn" />bool <b><a href="qimagewriter.html#supportsOption">supportsOption</a></b> (<i>self</i>, QImageIOHandler.ImageOption <i>option</i>)</li><li><div class="fn" />bool <b><a href="qimagewriter.html#write">write</a></b> (<i>self</i>, QImage <i>image</i>)</li></ul><h3>Static Methods</h3><ul><li><div class="fn" />unknown-type <b><a href="qimagewriter.html#supportedImageFormats">supportedImageFormats</a></b> ()</li></ul><a name="details" /><hr /><h2>Detailed Description</h2><p>The QImageWriter class provides a format independent interface
for writing images to files or other devices.</p>
<p>QImageWriter supports setting format specific options, such as
the gamma level, compression level and quality, prior to storing
the image. If you do not need such options, you can use <a href="qimage.html#save">QImage.save</a>() or <a href="qpixmap.html#save">QPixmap.save</a>() instead.</p>
<p>To store an image, you start by constructing a QImageWriter
object. Pass either a file name or a device pointer, and the image
format to QImageWriter's constructor. You can then set several
options, such as the gamma level (by calling <a href="qimagewriter.html#setGamma">setGamma</a>()) and quality (by
calling <a href="qimagewriter.html#setQuality">setQuality</a>()).
<a href="qimagewriter.html#canWrite">canWrite</a>() returns true if
QImageWriter can write the image (i.e., the image format is
supported and the device is open for writing). Call <a href="qimagewriter.html#write">write</a>() to write the image to the
device.</p>
<p>If any error occurs when writing the image, <a href="qimagewriter.html#write">write</a>() will return false. You can
then call <a href="qimagewriter.html#error">error</a>() to find the
type of error that occurred, or <a href="qimagewriter.html#errorString">errorString</a>() to get a human
readable description of what went wrong.</p>
<p>Call <a href="qimagewriter.html#supportedImageFormats">supportedImageFormats</a>()
for a list of formats that QImageWriter can write. QImageWriter
supports all built-in image formats, in addition to any image
format plugins that support writing.</p>
<hr /><h2>Type Documentation</h2><h3 class="fn"><a name="ImageWriterError-enum" />QImageWriter.ImageWriterError</h3><p>This enum describes errors that can occur when writing images
with <a href="qimagewriter.html">QImageWriter</a>.</p>
<table class="valuelist">
<tr class="odd" valign="top">
<th class="tblConst">Constant</th>
<th class="tblval">Value</th>
<th class="tbldscr">Description</th>
</tr>
<tr>
<td class="topAlign"><tt>QImageWriter.DeviceError</tt></td>
<td class="topAlign"><tt>1</tt></td>
<td class="topAlign"><a href="qimagewriter.html">QImageWriter</a>
encountered a device error when writing the image data. Consult
your device for more details on what went wrong.</td>
</tr>
<tr>
<td class="topAlign">
<tt>QImageWriter.UnsupportedFormatError</tt></td>
<td class="topAlign"><tt>2</tt></td>
<td class="topAlign">Qt does not support the requested image
format.</td>
</tr>
<tr>
<td class="topAlign"><tt>QImageWriter.UnknownError</tt></td>
<td class="topAlign"><tt>0</tt></td>
<td class="topAlign">An unknown error occurred. If you get this
value after calling <a href="qimagewriter.html#write">write</a>(),
it is most likely caused by a bug in <a href="qimagewriter.html">QImageWriter</a>.</td>
</tr>
</table>
<hr /><h2>Method Documentation</h2><h3 class="fn"><a name="QImageWriter" />QImageWriter.__init__ (<i>self</i>)</h3><p>Constructs an empty <a href="qimagewriter.html">QImageWriter</a>
object. Before writing, you must call <a href="qimagewriter.html#setFormat">setFormat</a>() to set an image
format, then <a href="qimagewriter.html#setDevice">setDevice</a>()
or <a href="qimagewriter.html#setFileName">setFileName</a>().</p>
<h3 class="fn"><a name="QImageWriter-2" />QImageWriter.__init__ (<i>self</i>, <a href="qiodevice.html">QIODevice</a> <i>device</i>, <a href="qbytearray.html">QByteArray</a> <i>format</i>)</h3><p>Constructs a <a href="qimagewriter.html">QImageWriter</a> object
using the device <i>device</i> and image format <i>format</i>.</p>
<h3 class="fn"><a name="QImageWriter-3" />QImageWriter.__init__ (<i>self</i>, QString <i>fileName</i>, <a href="qbytearray.html">QByteArray</a> <i>format</i> = QByteArray())</h3><p>Constructs a <a href="qimagewriter.html">QImageWriter</a>
objects that will write to a file with the name <i>fileName</i>,
using the image format <i>format</i>. If <i>format</i> is not
provided, <a href="qimagewriter.html">QImageWriter</a> will detect
the image format by inspecting the extension of
<i>fileName</i>.</p>
<h3 class="fn"><a name="canWrite" />bool QImageWriter.canWrite (<i>self</i>)</h3><p>Returns true if <a href="qimagewriter.html">QImageWriter</a> can
write the image; i.e., the image format is supported and the
assigned device is open for reading.</p>
<p><b>See also</b> <a href="qimagewriter.html#write">write</a>(),
<a href="qimagewriter.html#setDevice">setDevice</a>(), and <a href="qimagewriter.html#setFormat">setFormat</a>().</p>
<h3 class="fn"><a name="compression" />int QImageWriter.compression (<i>self</i>)</h3><p>Returns the compression of the image.</p>
<p><b>See also</b> <a href="qimagewriter.html#setCompression">setCompression</a>().</p>
<h3 class="fn"><a name="description" />QString QImageWriter.description (<i>self</i>)</h3><h3 class="fn"><a name="device" /><a href="qiodevice.html">QIODevice</a> QImageWriter.device (<i>self</i>)</h3><p>Returns the device currently assigned to <a href="qimagewriter.html">QImageWriter</a>, or 0 if no device has been
assigned.</p>
<p><b>See also</b> <a href="qimagewriter.html#setDevice">setDevice</a>().</p>
<h3 class="fn"><a name="error" /><a href="qimagewriter.html#ImageWriterError-enum">ImageWriterError</a> QImageWriter.error (<i>self</i>)</h3><p>Returns the type of error that last occurred.</p>
<p><b>See also</b> <a href="qimagewriter.html#ImageWriterError-enum">ImageWriterError</a> and
<a href="qimagewriter.html#errorString">errorString</a>().</p>
<h3 class="fn"><a name="errorString" />QString QImageWriter.errorString (<i>self</i>)</h3><p>Returns a human readable description of the last error that
occurred.</p>
<p><b>See also</b> <a href="qimagewriter.html#error">error</a>().</p>
<h3 class="fn"><a name="fileName" />QString QImageWriter.fileName (<i>self</i>)</h3><p>If the currently assigned device is a <a href="qfile.html">QFile</a>, or if <a href="qimagewriter.html#setFileName">setFileName</a>() has been called,
this function returns the name of the file <a href="qimagewriter.html">QImageWriter</a> writes to. Otherwise (i.e., if
no device has been assigned or the device is not a <a href="qfile.html">QFile</a>), an empty <a href="qstring.html">QString</a> is returned.</p>
<p><b>See also</b> <a href="qimagewriter.html#setFileName">setFileName</a>() and <a href="qimagewriter.html#setDevice">setDevice</a>().</p>
<h3 class="fn"><a name="format" /><a href="qbytearray.html">QByteArray</a> QImageWriter.format (<i>self</i>)</h3><p>Returns the format <a href="qimagewriter.html">QImageWriter</a>
uses for writing images.</p>
<p><b>See also</b> <a href="qimagewriter.html#setFormat">setFormat</a>().</p>
<h3 class="fn"><a name="gamma" />float QImageWriter.gamma (<i>self</i>)</h3><p>Returns the gamma level of the image.</p>
<p><b>See also</b> <a href="qimagewriter.html#setGamma">setGamma</a>().</p>
<h3 class="fn"><a name="quality" />int QImageWriter.quality (<i>self</i>)</h3><p>Returns the quality level of the image.</p>
<p><b>See also</b> <a href="qimagewriter.html#setQuality">setQuality</a>().</p>
<h3 class="fn"><a name="setCompression" />QImageWriter.setCompression (<i>self</i>, int <i>compression</i>)</h3><p>This is an image format specific function that set the
compression of an image. For image formats that do not support
setting the compression, this value is ignored.</p>
<p>The value range of <i>compression</i> depends on the image
format. For example, the "tiff" format supports two values, 0(no
compression) and 1(LZW-compression).</p>
<p><b>See also</b> <a href="qimagewriter.html#compression">compression</a>().</p>
<h3 class="fn"><a name="setDescription" />QImageWriter.setDescription (<i>self</i>, QString <i>description</i>)</h3><h3 class="fn"><a name="setDevice" />QImageWriter.setDevice (<i>self</i>, <a href="qiodevice.html">QIODevice</a> <i>device</i>)</h3><p>Sets <a href="qimagewriter.html">QImageWriter</a>'s device to
<i>device</i>. If a device has already been set, the old device is
removed from <a href="qimagewriter.html">QImageWriter</a> and is
otherwise left unchanged.</p>
<p>If the device is not already open, <a href="qimagewriter.html">QImageWriter</a> will attempt to open the
device in <a href="qiodevice.html#OpenModeFlag-enum">QIODevice.WriteOnly</a> mode by
calling open(). Note that this does not work for certain devices,
such as <a href="qprocess.html">QProcess</a>, <a href="qtcpsocket.html">QTcpSocket</a> and <a href="qudpsocket.html">QUdpSocket</a>, where more logic is required to
open the device.</p>
<p><b>See also</b> <a href="qimagewriter.html#device">device</a>()
and <a href="qimagewriter.html#setFileName">setFileName</a>().</p>
<h3 class="fn"><a name="setFileName" />QImageWriter.setFileName (<i>self</i>, QString <i>fileName</i>)</h3><p>Sets the file name of <a href="qimagewriter.html">QImageWriter</a> to <i>fileName</i>.
Internally, <a href="qimagewriter.html">QImageWriter</a> will
create a <a href="qfile.html">QFile</a> and open it in <a href="qiodevice.html#OpenModeFlag-enum">QIODevice.WriteOnly</a> mode,
and use this file when writing images.</p>
<p><b>See also</b> <a href="qimagewriter.html#fileName">fileName</a>() and <a href="qimagewriter.html#setDevice">setDevice</a>().</p>
<h3 class="fn"><a name="setFormat" />QImageWriter.setFormat (<i>self</i>, <a href="qbytearray.html">QByteArray</a> <i>format</i>)</h3><p>Sets the format <a href="qimagewriter.html">QImageWriter</a>
will use when writing images, to <i>format</i>. <i>format</i> is a
case insensitive text string. Example:</p>
<pre class="cpp">
<span class="type"><a href="qimagewriter.html">QImageWriter</a></span> writer;
writer<span class="operator">.</span>setFormat(<span class="string">"png"</span>); <span class="comment">// same as writer.setFormat("PNG");</span>
</pre>
<p>You can call <a href="qimagewriter.html#supportedImageFormats">supportedImageFormats</a>()
for the full list of formats <a href="qimagewriter.html">QImageWriter</a> supports.</p>
<p><b>See also</b> <a href="qimagewriter.html#format">format</a>().</p>
<h3 class="fn"><a name="setGamma" />QImageWriter.setGamma (<i>self</i>, float <i>gamma</i>)</h3><p>This is an image format specific function that sets the gamma
level of the image to <i>gamma</i>. For image formats that do not
support setting the gamma level, this value is ignored.</p>
<p>The value range of <i>gamma</i> depends on the image format. For
example, the "png" format supports a gamma range from 0.0 to
1.0.</p>
<p><b>See also</b> <a href="qimagewriter.html#gamma">gamma</a>()
and <a href="qimagewriter.html#quality">quality</a>().</p>
<h3 class="fn"><a name="setQuality" />QImageWriter.setQuality (<i>self</i>, int <i>quality</i>)</h3><p>This is an image format specific function that sets the quality
level of the image to <i>quality</i>. For image formats that do not
support setting the quality, this value is ignored.</p>
<p>The value range of <i>quality</i> depends on the image format.
For example, the "jpeg" format supports a quality range from 0 (low
quality, high compression) to 100 (high quality, low
compression).</p>
<p><b>See also</b> <a href="qimagewriter.html#quality">quality</a>().</p>
<h3 class="fn"><a name="setText" />QImageWriter.setText (<i>self</i>, QString <i>key</i>, QString <i>text</i>)</h3><p>Sets the image text associated with the key <i>key</i> to
<i>text</i>. This is useful for storing copyright information or
other information about the image. Example:</p>
<pre class="cpp">
<span class="type"><a href="qimage.html">QImage</a></span> image(<span class="string">"some/image.jpeg"</span>);
<span class="type"><a href="qimagewriter.html">QImageWriter</a></span> writer(<span class="string">"images/outimage.png"</span><span class="operator">,</span> <span class="string">"png"</span>);
writer<span class="operator">.</span>setText(<span class="string">"Author"</span><span class="operator">,</span> <span class="string">"John Smith"</span>);
writer<span class="operator">.</span><a href="qimagewriter.html#write">write</a>(image);
</pre>
<p>If you want to store a single block of data (e.g., a comment),
you can pass an empty key, or use a generic key like
"Description".</p>
<p>The key and text will be embedded into the image data after
calling <a href="qimagewriter.html#write">write</a>().</p>
<p>Support for this option is implemented through <a href="qimageiohandler.html#ImageOption-enum">QImageIOHandler.Description</a>.</p>
<p>This function was introduced in Qt 4.1.</p>
<p><b>See also</b> <a href="qimage.html#setText">QImage.setText</a>() and <a href="qimagereader.html#text">QImageReader.text</a>().</p>
<h3 class="fn"><a name="supportedImageFormats" />unknown-type QImageWriter.supportedImageFormats ()</h3><p>Returns the list of image formats supported by <a href="qimagewriter.html">QImageWriter</a>.</p>
<p>By default, Qt can write the following formats:</p>
<table class="generic">
<thead>
<tr class="qt-style">
<th>Format</th>
<th>Description</th>
</tr>
</thead>
<tr class="odd" valign="top">
<td>BMP</td>
<td>Windows Bitmap</td>
</tr>
<tr class="even" valign="top">
<td>JPG</td>
<td>Joint Photographic Experts Group</td>
</tr>
<tr class="odd" valign="top">
<td>JPEG</td>
<td>Joint Photographic Experts Group</td>
</tr>
<tr class="even" valign="top">
<td>PNG</td>
<td>Portable Network Graphics</td>
</tr>
<tr class="odd" valign="top">
<td>PPM</td>
<td>Portable Pixmap</td>
</tr>
<tr class="even" valign="top">
<td>TIFF</td>
<td>Tagged Image File Format</td>
</tr>
<tr class="odd" valign="top">
<td>XBM</td>
<td>X11 Bitmap</td>
</tr>
<tr class="even" valign="top">
<td>XPM</td>
<td>X11 Pixmap</td>
</tr>
</table>
<p>Reading and writing SVG files is supported through Qt's <a href="qtsvg.html">SVG Module</a>.</p>
<p>Note that the <a href="qapplication.html">QApplication</a>
instance must be created before this function is called.</p>
<p><b>See also</b> <a href="qimagewriter.html#setFormat">setFormat</a>(), <a href="qimagereader.html#supportedImageFormats">QImageReader.supportedImageFormats</a>(),
and <a href="qimageioplugin.html">QImageIOPlugin</a>.</p>
<h3 class="fn"><a name="supportsOption" />bool QImageWriter.supportsOption (<i>self</i>, <a href="qimageiohandler.html#ImageOption-enum">QImageIOHandler.ImageOption</a> <i>option</i>)</h3><p>Returns true if the writer supports <i>option</i>; otherwise
returns false.</p>
<p>Different image formats support different options. Call this
function to determine whether a certain option is supported by the
current format. For example, the PNG format allows you to embed
text into the image's metadata (see text()).</p>
<pre class="cpp">
<span class="type"><a href="qimagewriter.html">QImageWriter</a></span> writer(fileName);
<span class="keyword">if</span> (writer<span class="operator">.</span>supportsOption(<span class="type"><a href="qimageiohandler.html">QImageIOHandler</a></span><span class="operator">.</span>Description))
writer<span class="operator">.</span><a href="qimagewriter.html#setText">setText</a>(<span class="string">"Author"</span><span class="operator">,</span> <span class="string">"John Smith"</span>);
</pre>
<p>Options can be tested after the writer has been associated with
a format.</p>
<p>This function was introduced in Qt 4.2.</p>
<p><b>See also</b> <a href="qimagereader.html#supportsOption">QImageReader.supportsOption</a>()
and <a href="qimagewriter.html#setFormat">setFormat</a>().</p>
<h3 class="fn"><a name="write" />bool QImageWriter.write (<i>self</i>, <a href="qimage.html">QImage</a> <i>image</i>)</h3><p>Writes the image <i>image</i> to the assigned device or file
name. Returns true on success; otherwise returns false. If the
operation fails, you can call <a href="qimagewriter.html#error">error</a>() to find the type of error
that occurred, or <a href="qimagewriter.html#errorString">errorString</a>() to get a human
readable description of the error.</p>
<p><b>See also</b> <a href="qimagewriter.html#canWrite">canWrite</a>(), <a href="qimagewriter.html#error">error</a>(), and <a href="qimagewriter.html#errorString">errorString</a>().</p>
<address><hr /><div align="center"><table border="0" cellspacing="0" width="100%"><tr class="address"><td align="left" width="25%">PyQt 4.12.1 for X11</td><td align="center" width="50%">Copyright © <a href="http://www.riverbankcomputing.com">Riverbank Computing Ltd</a> and <a href="http://www.qt.io">The Qt Company</a> 2015</td><td align="right" width="25%">Qt 4.8.7</td></tr></table></div></address></body></html>
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