class_qwt_raster_data.html

QWT5.01用于Qt开发的二维图形库程序

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<p>
Discard a raster. 
<p>
After the composition of an image <a class="el" href="class_qwt_plot_spectrogram.html">QwtPlotSpectrogram</a> calls <a class="el" href="class_qwt_raster_data.html#369a5f525814bf569e01f88fbd8ddb5b">discardRaster()</a>.<p>
The default implementation does nothing, but if data has been loaded in <a class="el" href="class_qwt_raster_data.html#8405182366702abc965a2f938ccf1f14">initRaster()</a>, it could deleted now.<p>
<dl compact><dt><b>See also:</b></dt><dd><a class="el" href="class_qwt_raster_data.html#8405182366702abc965a2f938ccf1f14">initRaster()</a>, <a class="el" href="class_qwt_raster_data.html#6396fc013fcec893b1e8cea4cf03691e">value()</a> </dd></dl>

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Definition at line <a class="el" href="qwt__raster__data_8cpp-source.html#l00236">236</a> of file <a class="el" href="qwt__raster__data_8cpp-source.html">qwt_raster_data.cpp</a>.    </td>
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<a class="anchor" name="8405182366702abc965a2f938ccf1f14"></a><!-- doxytag: member="QwtRasterData::initRaster" ref="8405182366702abc965a2f938ccf1f14" args="(const QwtDoubleRect &amp;, const QSize &amp;raster)" --><p>
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          <td class="md" nowrap valign="top">void QwtRasterData::initRaster           </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="md" nowrap valign="top">const QwtDoubleRect &amp;&nbsp;</td>
          <td class="mdname" nowrap>, </td>
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          <td class="md" nowrap>const QSize &amp;&nbsp;</td>
          <td class="mdname" nowrap> <em>raster</em></td>
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          <td class="md">)&nbsp;</td>
          <td class="md" colspan="2"><code> [virtual]</code></td>
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<p>
Initialize a raster. 
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Before the composition of an image <a class="el" href="class_qwt_plot_spectrogram.html">QwtPlotSpectrogram</a> calls initRaster, announcing the area and its resolution that will be requested.<p>
The default implementation does nothing, but for data sets that are stored in files, it might be good idea to reimplement initRaster, where the data is resampled and loaded into memory.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
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    <tr><td valign="top"></td><td valign="top"><em>rect</em>&nbsp;</td><td>Area of the raster </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>raster</em>&nbsp;</td><td>Number of horizontal and vertical pixels</td></tr>
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<dl compact><dt><b>See also:</b></dt><dd><a class="el" href="class_qwt_raster_data.html#8405182366702abc965a2f938ccf1f14">initRaster()</a>, <a class="el" href="class_qwt_raster_data.html#6396fc013fcec893b1e8cea4cf03691e">value()</a> </dd></dl>

<p>
Definition at line <a class="el" href="qwt__raster__data_8cpp-source.html#l00222">222</a> of file <a class="el" href="qwt__raster__data_8cpp-source.html">qwt_raster_data.cpp</a>.    </td>
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<a class="anchor" name="6c282a2457d2307d26afe9b84cc0b775"></a><!-- doxytag: member="QwtRasterData::range" ref="6c282a2457d2307d26afe9b84cc0b775" args="() const =0" --><p>
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          <td class="md" nowrap valign="top">virtual <a class="el" href="class_qwt_double_interval.html">QwtDoubleInterval</a> QwtRasterData::range           </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="mdname1" valign="top" nowrap>          </td>
          <td class="md" valign="top">&nbsp;)&nbsp;</td>
          <td class="md" nowrap> const<code> [pure virtual]</code></td>
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<dl compact><dt><b>Returns:</b></dt><dd>the range of the values </dd></dl>
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<a class="anchor" name="81e17cbcf24c941526088e6458ba347f"></a><!-- doxytag: member="QwtRasterData::rasterHint" ref="81e17cbcf24c941526088e6458ba347f" args="(const QwtDoubleRect &amp;) const " --><p>
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          <td class="md" nowrap valign="top">QSize QwtRasterData::rasterHint           </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="md" nowrap valign="top">const QwtDoubleRect &amp;&nbsp;</td>
          <td class="mdname1" valign="top" nowrap>          </td>
          <td class="md" valign="top">&nbsp;)&nbsp;</td>
          <td class="md" nowrap> const<code> [virtual]</code></td>
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<p>
Find the raster of the data for an area. 
<p>
The resolution is the number of horizontal and vertical pixels that the data can return for an area. An invalid resolution indicates that the data can return values for any detail level.<p>
The resolution will limit the size of the image that is rendered from the data. F.e. this might be important when printing a spectrogram to a A0 printer with 600 dpi.<p>
The default implementation returns an invalid resolution (size)<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
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    <tr><td valign="top"></td><td valign="top"><em>rect</em>&nbsp;</td><td>In most implementations the resolution of the data doesn't depend on the requested rectangle.</td></tr>
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<dl compact><dt><b>Returns:</b></dt><dd>Resolution, as number of horizontal and vertical pixels </dd></dl>

<p>
Definition at line <a class="el" href="qwt__raster__data_8cpp-source.html#l00258">258</a> of file <a class="el" href="qwt__raster__data_8cpp-source.html">qwt_raster_data.cpp</a>.    </td>
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<a class="anchor" name="6396fc013fcec893b1e8cea4cf03691e"></a><!-- doxytag: member="QwtRasterData::value" ref="6396fc013fcec893b1e8cea4cf03691e" args="(double x, double y) const =0" --><p>
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          <td class="md" nowrap valign="top">virtual double QwtRasterData::value           </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="md" nowrap valign="top">double&nbsp;</td>
          <td class="mdname" nowrap> <em>x</em>, </td>
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          <td class="md" nowrap>double&nbsp;</td>
          <td class="mdname" nowrap> <em>y</em></td>
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          <td class="md">)&nbsp;</td>
          <td class="md" colspan="2"> const<code> [pure virtual]</code></td>
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<dl compact><dt><b>Returns:</b></dt><dd>the value at a raster position </dd></dl>
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