[FEATURE] Allow classifying paletted renderer using unique values

from a raster layer Adds an easy way to style discrete rasters such as landuse classes using the Paletted renderer. Just select the Paletted renderer, pick a band, then hit the "Add Unique Values" button. The unique pixel values will be fetched from the layer and a color assigned to each using the currently selected color ramp. Fix #14845 Sponsored by - Stéphane Henriod - Satelligence (http://satelligence.com/) - Bird's Eye View (https://www.birdseyeviewgis.com/) - + other anonymous backers
qgis · Apr 3, 2017 · d03844d · d03844d
1 parent c8b728a
commit d03844d
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diff --git a/python/core/raster/qgspalettedrasterrenderer.sip b/python/core/raster/qgspalettedrasterrenderer.sip
@@ -40,6 +40,7 @@ class QgsPalettedRasterRenderer : QgsRasterRenderer
     static QgsPalettedRasterRenderer::ClassData classDataFromString( const QString &string );
     static QgsPalettedRasterRenderer::ClassData classDataFromFile( const QString &path );
     static QString classDataToString( const QgsPalettedRasterRenderer::ClassData &classes );
+    static QgsPalettedRasterRenderer::ClassData classDataFromRaster( QgsRasterInterface *raster, int bandNumber, QgsColorRamp *ramp = 0 );
 
   private:
 

diff --git a/src/core/raster/qgspalettedrasterrenderer.cpp b/src/core/raster/qgspalettedrasterrenderer.cpp
@@ -401,6 +401,50 @@ QString QgsPalettedRasterRenderer::classDataToString( const QgsPalettedRasterRen
   return out.join( '\n' );
 }
 
+QgsPalettedRasterRenderer::ClassData QgsPalettedRasterRenderer::classDataFromRaster( QgsRasterInterface *raster, int bandNumber, QgsColorRamp *ramp )
+{
+  if ( !raster )
+    return ClassData();
+
+  // get min and max value from raster
+  QgsRasterBandStats stats = raster->bandStatistics( bandNumber, QgsRasterBandStats::Min | QgsRasterBandStats::Max );
+  double min = stats.minimumValue;
+  double max = stats.maximumValue;
+  // need count of every individual value
+  int bins = ceil( max - min ) + 1;
+
+  QgsRasterHistogram histogram = raster->histogram( bandNumber, bins, min, max );
+  double interval = ( histogram.maximum - histogram.minimum + 1 ) / histogram.binCount;
+
+  ClassData data;
+
+  double currentValue = histogram.minimum;
+  double presentValues = 0;
+  for ( int idx = 0; idx < histogram.binCount; ++idx )
+  {
+    int count = histogram.histogramVector.at( idx );
+    if ( count > 0 )
+    {
+      data << Class( currentValue, QColor(), QString::number( currentValue ) );
+      presentValues++;
+    }
+    currentValue += interval;
+  }
+
+  // assign colors from ramp
+  if ( ramp )
+  {
+    int i = 0;
+    QgsPalettedRasterRenderer::ClassData::iterator cIt = data.begin();
+    for ( ; cIt != data.end(); ++cIt )
+    {
+      cIt->color = ramp->color( i / presentValues );
+      i++;
+    }
+  }
+  return data;
+}
+
 void QgsPalettedRasterRenderer::updateArrays()
 {
   // find maximum color index

diff --git a/src/core/raster/qgspalettedrasterrenderer.h b/src/core/raster/qgspalettedrasterrenderer.h
@@ -135,6 +135,13 @@ class CORE_EXPORT QgsPalettedRasterRenderer: public QgsRasterRenderer
      */
     static QString classDataToString( const QgsPalettedRasterRenderer::ClassData &classes );
 
+    /**
+     * Generates class data from a \a raster, for the specified \a bandNumber. An optional
+     * color \a ramp can be specified to automatically assign colors from the ramp.
+     * @note added in QGIS 3.0
+     */
+    static QgsPalettedRasterRenderer::ClassData classDataFromRaster( QgsRasterInterface *raster, int bandNumber, QgsColorRamp *ramp = nullptr );
+
   private:
 
     int mBand;

diff --git a/src/gui/raster/qgspalettedrendererwidget.cpp b/src/gui/raster/qgspalettedrendererwidget.cpp
@@ -93,6 +93,7 @@ QgsPalettedRendererWidget::QgsPalettedRendererWidget( QgsRasterLayer *layer, con
   connect( mAddEntryButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::addEntry );
   connect( mLoadFromFileButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::loadColorTable );
   connect( mExportToFileButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::saveColorTable );
+  connect( mClassifyButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::classify );
 }
 
 QgsRasterRenderer *QgsPalettedRendererWidget::renderer()
@@ -367,6 +368,23 @@ void QgsPalettedRendererWidget::saveColorTable()
   }
 }
 
+void QgsPalettedRendererWidget::classify()
+{
+  if ( mRasterLayer )
+  {
+    QgsRasterDataProvider *provider = mRasterLayer->dataProvider();
+    if ( !provider )
+    {
+      return;
+    }
+
+    std::unique_ptr< QgsColorRamp > ramp( btnColorRamp->colorRamp() );
+    QgsPalettedRasterRenderer::ClassData data = QgsPalettedRasterRenderer::classDataFromRaster( provider, mBandComboBox->currentData().toInt(), ramp.get() );
+    mModel->setClassData( data );
+    emit widgetChanged();
+  }
+}
+
 //
 // QgsPalettedRendererModel
 //

diff --git a/src/gui/raster/qgspalettedrendererwidget.h b/src/gui/raster/qgspalettedrendererwidget.h
@@ -109,6 +109,7 @@ class GUI_EXPORT QgsPalettedRendererWidget: public QgsRasterRendererWidget, priv
     void applyColorRamp();
     void loadColorTable();
     void saveColorTable();
+    void classify();
 
 };
 

diff --git a/src/ui/qgspalettedrendererwidgetbase.ui b/src/ui/qgspalettedrendererwidgetbase.ui
@@ -60,6 +60,13 @@
    </item>
    <item row="3" column="0">
     <layout class="QHBoxLayout" name="horizontalLayout_3">
+     <item>
+      <widget class="QPushButton" name="mClassifyButton">
+       <property name="text">
+        <string>Classify</string>
+       </property>
+      </widget>
+     </item>
      <item>
       <widget class="QPushButton" name="mAddEntryButton">
        <property name="toolTip">

diff --git a/tests/src/python/test_qgsrasterlayer.py b/tests/src/python/test_qgsrasterlayer.py
@@ -35,7 +35,8 @@
                        QgsPalettedRasterRenderer,
                        QgsSingleBandGrayRenderer,
                        QgsSingleBandPseudoColorRenderer,
-                       QgsLimitedRandomColorRamp)
+                       QgsLimitedRandomColorRamp,
+                       QgsGradientColorRamp)
 from utilities import unitTestDataPath
 from qgis.testing import start_app, unittest
 
@@ -553,6 +554,70 @@ def testPalettedClassDataToString(self):
         self.assertEqual(QgsPalettedRasterRenderer.classDataToString(classes),
                          '3 255 0 0 255 class 1\n4 0 255 0 255 class 2')
 
+    def testPalettedClassDataFromLayer(self):
+        # no layer
+        classes = QgsPalettedRasterRenderer.classDataFromRaster(None, 1)
+        self.assertFalse(classes)
+
+        # 10 class layer
+        path = os.path.join(unitTestDataPath('raster'),
+                            'with_color_table.tif')
+        info = QFileInfo(path)
+        base_name = info.baseName()
+        layer10 = QgsRasterLayer(path, base_name)
+        classes = QgsPalettedRasterRenderer.classDataFromRaster(layer10.dataProvider(), 1)
+        self.assertEqual(len(classes), 10)
+        self.assertEqual(classes[0].value, 1)
+        self.assertEqual(classes[0].label, '1')
+        self.assertEqual(classes[1].value, 2)
+        self.assertEqual(classes[1].label, '2')
+        self.assertEqual(classes[2].value, 3)
+        self.assertEqual(classes[2].label, '3')
+        self.assertEqual(classes[3].value, 4)
+        self.assertEqual(classes[3].label, '4')
+        self.assertEqual(classes[4].value, 5)
+        self.assertEqual(classes[4].label, '5')
+        self.assertEqual(classes[5].value, 6)
+        self.assertEqual(classes[5].label, '6')
+        self.assertEqual(classes[6].value, 7)
+        self.assertEqual(classes[6].label, '7')
+        self.assertEqual(classes[7].value, 8)
+        self.assertEqual(classes[7].label, '8')
+        self.assertEqual(classes[8].value, 9)
+        self.assertEqual(classes[8].label, '9')
+        self.assertEqual(classes[9].value, 10)
+        self.assertEqual(classes[9].label, '10')
+
+        # bad band
+        with self.assertRaises(Exception):
+            classes = QgsPalettedRasterRenderer.classDataFromRaster(layer10.dataProvider(), 10101010)
+
+        # with ramp
+        r = QgsGradientColorRamp(QColor(200, 0, 0, 100), QColor(0, 200, 0, 200))
+        classes = QgsPalettedRasterRenderer.classDataFromRaster(layer10.dataProvider(), 1, r)
+        self.assertEqual(len(classes), 10)
+        self.assertEqual(classes[0].color.name(), '#c80000')
+        self.assertEqual(classes[1].color.name(), '#b41400')
+        self.assertEqual(classes[2].color.name(), '#a02800')
+        self.assertEqual(classes[3].color.name(), '#8c3c00')
+        self.assertEqual(classes[4].color.name(), '#785000')
+        self.assertEqual(classes[5].color.name(), '#646400')
+        self.assertEqual(classes[6].color.name(), '#507800')
+        self.assertEqual(classes[7].color.name(), '#3c8c00')
+        self.assertEqual(classes[8].color.name(), '#28a000')
+        self.assertEqual(classes[9].color.name(), '#14b400')
+
+        # 30 class layer
+        path = os.path.join(unitTestDataPath('raster'),
+                            'unique_1.tif')
+        info = QFileInfo(path)
+        base_name = info.baseName()
+        layer10 = QgsRasterLayer(path, base_name)
+        classes = QgsPalettedRasterRenderer.classDataFromRaster(layer10.dataProvider(), 1)
+        self.assertEqual(len(classes), 30)
+        expected = [11, 21, 22, 24, 31, 82, 2002, 2004, 2014, 2019, 2027, 2029, 2030, 2080, 2081, 2082, 2088, 2092, 2097, 2098, 2099, 2105, 2108, 2110, 2114, 2118, 2126, 2152, 2184, 2220]
+        self.assertEqual([c.value for c in classes], expected)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/testdata/raster/unique_1.tif b/tests/testdata/raster/unique_1.tif