Raster attributes and raster maptips

qgis · Nov 9, 2022 · b37f5f4 · b37f5f4
1 parent 5fe715a
commit b37f5f4
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diff --git a/resources/function_help/json/raster_attributes b/resources/function_help/json/raster_attributes
@@ -0,0 +1,21 @@
+{
+  "name": "raster_attributes",
+  "type": "function",
+  "groups": ["Rasters"],
+  "description": "Returns a map with the fields names as keys and the raster attribute table values as values from the attribute table entry that matches the given raster value .",
+  "arguments": [{
+    "arg": "layer",
+    "description": "the name or id of a raster layer"
+  }, {
+    "arg": "band",
+    "description": "the band number to sample the value from and for the associated attribute table lookup."
+  }, {
+    "arg": "value",
+    "description": "raster value"
+  }],
+  "examples": [{
+    "expression": "raster_attributes('vegetation', 1, raster_value('vegetation', 1, make_point(1,1)))",
+    "returns": "{'class': 'Vegetated', 'subclass': 'Trees'}"
+  }],
+  "tags": ["provider", "point", "raster", "found", "attributes"]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -1697,6 +1697,56 @@ static QVariant fcnRasterValue( const QVariantList &values, const QgsExpressionC
   return std::isnan( value ) ? QVariant() : value;
 }
 
+static QVariant fcnRasterAttributes( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  QgsRasterLayer *layer = QgsExpressionUtils::getRasterLayer( values.at( 0 ), parent );
+  if ( !layer || !layer->dataProvider() )
+  {
+    parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster layer." ) );
+    return QVariant();
+  }
+
+  int bandNb = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
+  if ( bandNb < 1 || bandNb > layer->bandCount() )
+  {
+    parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster band number." ) );
+    return QVariant();
+  }
+
+  const double value = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
+  if ( std::isnan( value ) )
+  {
+    parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster value." ) );
+    return QVariant();
+  }
+
+  if ( ! layer->dataProvider()->attributeTable( bandNb ) )
+  {
+    return QVariant();
+  }
+
+  const QVariantList data { layer->dataProvider()->attributeTable( bandNb )->row( value ) };
+  if ( data.isEmpty() )
+  {
+    return QVariant();
+  }
+
+  QVariantMap result;
+  const QList<QgsRasterAttributeTable::Field> fields { layer->dataProvider()->attributeTable( bandNb )->fields() };
+  for ( int idx = 0; idx < static_cast<int>( fields.count( ) ) && idx < static_cast<int>( data.count() ); ++idx )
+  {
+    const QgsRasterAttributeTable::Field field { fields.at( idx ) };
+    if ( field.isColor() || field.isRamp() )
+    {
+      continue;
+    }
+    result.insert( fields.at( idx ).name, data.at( idx ) );
+  }
+
+  return result;
+}
+
+
 static QVariant fcnFeature( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
 {
   if ( !context )
@@ -8470,6 +8520,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "env" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "name" ) ), fcnEnvVar, QStringLiteral( "General" ), QString() )
         << new QgsWithVariableExpressionFunction()
         << new QgsStaticExpressionFunction( QStringLiteral( "raster_value" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "layer" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "band" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "point" ) ), fcnRasterValue, QStringLiteral( "Rasters" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "raster_attributes" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "layer" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "band" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "point" ) ), fcnRasterAttributes, QStringLiteral( "Rasters" ) )
 
         // functions for arrays
         << new QgsArrayForeachExpressionFunction()

diff --git a/src/gui/qgsmaptip.cpp b/src/gui/qgsmaptip.cpp
@@ -17,6 +17,7 @@
 #include "qgsmapcanvas.h"
 #include "qgsmaptool.h"
 #include "qgsvectorlayer.h"
+#include "qgsrasterlayer.h"
 #include "qgsexpression.h"
 #include "qgslogger.h"
 #include "qgssettings.h"
@@ -313,6 +314,31 @@ QString QgsMapTip::fetchFeature( QgsMapLayer *layer, QgsPointXY &mapPosition, Qg
   return tipString;
 }
 
+QString QgsMapTip::fetchRaster( QgsMapLayer *layer, QgsPointXY &mapPosition, QgsMapCanvas *mapCanvas )
+{
+  QgsRasterLayer *rlayer = qobject_cast<QgsRasterLayer *>( layer );
+  if ( !rlayer )
+    return QString();
+
+  if ( !layer->isInScaleRange( mapCanvas->mapSettings().scale() ) )
+  {
+    return QString();
+  }
+
+  const QgsPointXY mappedPosition { mapCanvas->mapSettings().mapToLayerCoordinates( layer, mapPosition ) };
+
+  if ( ! layer->extent().contains( mappedPosition ) )
+  {
+    return QString( );
+  }
+
+  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) );
+  context.appendScope( QgsExpressionContextUtils::mapSettingsScope( mapCanvas->mapSettings() ) );
+
+  const QString mapTip = rlayer->mapTipTemplate();
+
+}
+
 void QgsMapTip::applyFontSettings()
 {
   const QgsSettings settings;

diff --git a/src/gui/qgsmaptip.h b/src/gui/qgsmaptip.h
@@ -97,6 +97,11 @@ class GUI_EXPORT QgsMapTip : public QWidget
                           QgsPointXY &mapPosition,
                           QgsMapCanvas *mapCanvas );
 
+    // Sample the raster and get the maptip text
+    QString fetchRaster( QgsMapLayer *layer,
+                         QgsPointXY &mapPosition,
+                         QgsMapCanvas *mapCanvas );
+
     QString replaceText(
       QString displayText, QgsVectorLayer *layer, QgsFeature &feat );