[FEATURE] Implement saving paletted raster renderer color tables

Use the .clr/gdal file format, but add the labels on the ends of
the lines. Seems other importers like ArcMap just ignore these.

python/core/raster/qgspalettedrasterrenderer.sip

@@ -39,6 +39,7 @@ class QgsPalettedRasterRenderer : QgsRasterRenderer
     static QgsPalettedRasterRenderer::ClassData colorTableToClassData( const QList<QgsColorRampShader::ColorRampItem> &table );
     static QgsPalettedRasterRenderer::ClassData classDataFromString( const QString &string );
     static QgsPalettedRasterRenderer::ClassData classDataFromFile( const QString &path );
+    static QString classDataToString( const QgsPalettedRasterRenderer::ClassData &classes );
 
   private:
 

src/core/raster/qgspalettedrasterrenderer.cpp

@@ -326,9 +326,11 @@ QgsPalettedRasterRenderer::ClassData QgsPalettedRasterRenderer::classDataFromStr
         break;
       }
 
-      case 4:
-      case 5:
+      default:
       {
+        if ( lineParts.count() < 4 )
+          continue;
+
         int value = lineParts.at( 0 ).toInt( &ok );
         if ( !ok )
           continue;
@@ -346,14 +348,20 @@ QgsPalettedRasterRenderer::ClassData QgsPalettedRasterRenderer::classDataFromStr
           c = QColor( r, g, b );
         }
 
-        if ( lineParts.count() == 5 )
+        if ( lineParts.count() >= 5 )
         {
           double alpha = lineParts.at( 4 ).toDouble( &ok );
           if ( ok )
             c.setAlpha( alpha );
         }
 
-        classes << Class( value, c );
+        QString label;
+        if ( lineParts.count() > 5 )
+        {
+          label = lineParts.mid( 5 ).join( ' ' );
+        }
+
+        classes << Class( value, c, label );
         break;
       }
     }
@@ -375,6 +383,24 @@ QgsPalettedRasterRenderer::ClassData QgsPalettedRasterRenderer::classDataFromFil
   return classDataFromString( input );
 }
 
+QString QgsPalettedRasterRenderer::classDataToString( const QgsPalettedRasterRenderer::ClassData &classes )
+{
+  QStringList out;
+  // must be sorted
+  QgsPalettedRasterRenderer::ClassData cd = classes;
+  std::sort( cd.begin(), cd.end(), []( const Class & a, const Class & b ) -> bool
+  {
+    return a.value < b.value;
+  } );
+
+  Q_FOREACH ( const Class &c, cd )
+  {
+    out << QString( "%1 %2 %3 %4 %5 %6" ).arg( c.value ).arg( c.color.red() )
+        .arg( c.color.green() ).arg( c.color.blue() ).arg( c.color.alpha() ).arg( c.label );
+  }
+  return out.join( '\n' );
+}
+
 void QgsPalettedRasterRenderer::updateArrays()
 {
   // find maximum color index

src/core/raster/qgspalettedrasterrenderer.h

@@ -117,6 +117,7 @@ class CORE_EXPORT QgsPalettedRasterRenderer: public QgsRasterRenderer
      * Converts a \a string containing a color table or class data to to paletted renderer class data.
      * @note added in QGIS 3.0
      * @see classDataFromFile()
+     * @see classDataToString()
      */
     static QgsPalettedRasterRenderer::ClassData classDataFromString( const QString &string );
 
@@ -127,6 +128,13 @@ class CORE_EXPORT QgsPalettedRasterRenderer: public QgsRasterRenderer
      */
     static QgsPalettedRasterRenderer::ClassData classDataFromFile( const QString &path );
 
+    /**
+     * Converts classes to a string representation, using the .clr/gdal color table file format.
+     * @note added in QGIS 3.0
+     * @see classDataFromString()
+     */
+    static QString classDataToString( const QgsPalettedRasterRenderer::ClassData &classes );
+
   private:
 
     int mBand;

src/gui/raster/qgspalettedrendererwidget.cpp

@@ -92,6 +92,7 @@ QgsPalettedRendererWidget::QgsPalettedRendererWidget( QgsRasterLayer *layer, con
   connect( mDeleteEntryButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::deleteEntry );
   connect( mAddEntryButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::addEntry );
   connect( mLoadFromFileButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::loadColorTable );
+  connect( mExportToFileButton, &QPushButton::clicked, this, &QgsPalettedRendererWidget::saveColorTable );
 }
 
 QgsRasterRenderer *QgsPalettedRendererWidget::renderer()
@@ -336,6 +337,36 @@ void QgsPalettedRendererWidget::loadColorTable()
   }
 }
 
+void QgsPalettedRendererWidget::saveColorTable()
+{
+  QgsSettings settings;
+  QString lastDir = settings.value( QStringLiteral( "lastColorMapDir" ), QDir::homePath() ).toString();
+  QString fileName = QFileDialog::getSaveFileName( this, tr( "Save file" ), lastDir, tr( "Text (*.clr)" ) );
+  if ( !fileName.isEmpty() )
+  {
+    if ( !fileName.endsWith( QLatin1String( ".clr" ), Qt::CaseInsensitive ) )
+    {
+      fileName = fileName + ".clr";
+    }
+
+    QFile outputFile( fileName );
+    if ( outputFile.open( QFile::WriteOnly | QIODevice::Truncate ) )
+    {
+      QTextStream outputStream( &outputFile );
+      outputStream << QgsPalettedRasterRenderer::classDataToString( mModel->classData() );
+      outputStream.flush();
+      outputFile.close();
+
+      QFileInfo fileInfo( fileName );
+      settings.setValue( QStringLiteral( "lastColorMapDir" ), fileInfo.absoluteDir().absolutePath() );
+    }
+    else
+    {
+      QMessageBox::warning( this, tr( "Write access denied" ), tr( "Write access denied. Adjust the file permissions and try again.\n\n" ) );
+    }
+  }
+}
+
 //
 // QgsPalettedRendererModel
 //

src/gui/raster/qgspalettedrendererwidget.h

@@ -108,6 +108,8 @@ class GUI_EXPORT QgsPalettedRendererWidget: public QgsRasterRendererWidget, priv
     void changeLabel();
     void applyColorRamp();
     void loadColorTable();
+    void saveColorTable();
+
 };
 
 #endif // QGSPALETTEDRENDERERWIDGET_H

tests/src/python/test_qgsrasterlayer.py

@@ -480,6 +480,19 @@ class TestQgsRasterLayer(unittest.TestCase):
         self.assertEqual(classes[4].color.name(), '#0000ff')
         self.assertEqual(classes[4].color.alpha(), 255)
 
+        # qgis style, with labels
+        qgis = '3 255 0 0 255 class 1\n4 0 255 0 200 class 2'
+        classes = QgsPalettedRasterRenderer.classDataFromString(qgis)
+        self.assertEqual(len(classes), 2)
+        self.assertEqual(classes[0].value, 3)
+        self.assertEqual(classes[0].color.name(), '#ff0000')
+        self.assertEqual(classes[0].color.alpha(), 255)
+        self.assertEqual(classes[0].label, 'class 1')
+        self.assertEqual(classes[1].value, 4)
+        self.assertEqual(classes[1].color.name(), '#00ff00')
+        self.assertEqual(classes[1].color.alpha(), 200)
+        self.assertEqual(classes[1].label, 'class 2')
+
         # some bad inputs
         bad = ''
         classes = QgsPalettedRasterRenderer.classDataFromString(bad)
@@ -496,9 +509,6 @@ class TestQgsRasterLayer(unittest.TestCase):
         bad = '1 255 a 0'
         classes = QgsPalettedRasterRenderer.classDataFromString(bad)
         self.assertEqual(len(classes), 1)
-        bad = '1 255 255 0 0 0 0 0 0 0'
-        classes = QgsPalettedRasterRenderer.classDataFromString(bad)
-        self.assertEqual(len(classes), 0)
 
     def testLoadPalettedClassDataFromFile(self):
         # bad file
@@ -533,5 +543,16 @@ class TestQgsRasterLayer(unittest.TestCase):
         self.assertEqual(classes[9].value, 10)
         self.assertEqual(classes[9].color.name(), '#ffb600')
 
+    def testPalettedClassDataToString(self):
+        classes = [QgsPalettedRasterRenderer.Class(1, QColor(0, 255, 0), 'class 2'),
+                   QgsPalettedRasterRenderer.Class(3, QColor(255, 0, 0), 'class 1')]
+        self.assertEqual(QgsPalettedRasterRenderer.classDataToString(classes), '1 0 255 0 255 class 2\n3 255 0 0 255 class 1')
+        # must be sorted by value to work OK in ArcMap
+        classes = [QgsPalettedRasterRenderer.Class(4, QColor(0, 255, 0), 'class 2'),
+                   QgsPalettedRasterRenderer.Class(3, QColor(255, 0, 0), 'class 1')]
+        self.assertEqual(QgsPalettedRasterRenderer.classDataToString(classes),
+                         '3 255 0 0 255 class 1\n4 0 255 0 255 class 2')
+
+
 if __name__ == '__main__':
     unittest.main()

tests/testdata/raster/test.clr

@@ -0,0 +1,10 @@
+1 0 0 0
+2 200 200 200
+3 0 110 0
+4 110 65 0
+5 0 0 255
+6 0 89 255
+7 0 174 255
+8 0 255 246
+9 238 255 0
+10 255 182 0