Merge pull request #9362 from pblottiere/legend_json

Add json format for legend

python/core/auto_generated/layertree/qgslayertreemodellegendnode.sip.in

@@ -94,6 +94,18 @@ Entry point called from QgsLegendRenderer to do the rendering.
 Default implementation calls drawSymbol() and drawSymbolText() methods.
 
 If ctx is ``None``, this is just first stage when preparing layout - without actual rendering.
+%End
+
+    void exportToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json );
+%Docstring
+Entry point called from QgsLegendRenderer to do the rendering in a
+JSON object.
+
+:param settings: Legend layout configuration
+:param context: Rendering context
+:param json: The json object to update
+
+.. versionadded:: 3.8
 %End
 
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
@@ -105,6 +117,17 @@ Draws symbol on the left side of the item
 :param itemHeight: Minimal height of the legend item - used for correct positioning when rendering
 
 :return: Real size of the symbol (may be bigger than "normal" symbol size from settings)
+%End
+
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+%Docstring
+Adds a symbol in base64 string within a JSON object with the key "icon".
+
+:param settings: Legend layout configuration
+:param context: Rendering context
+:param json: The json object to update
+
+.. versionadded:: 3.8
 %End
 
     virtual QSizeF drawSymbolText( const QgsLegendSettings &settings, ItemContext *ctx, QSizeF symbolSize ) const;
@@ -116,6 +139,16 @@ Draws label on the right side of the item
 :param symbolSize: Real size of the associated symbol - used for correct positioning when rendering
 
 :return: Size of the label (may span multiple lines)
+%End
+
+    void exportSymbolTextToJson( const QgsLegendSettings &settings, QJsonObject &json ) const;
+%Docstring
+Adds a label in a JSON object with the key "title".
+
+:param settings: Legend layout configuration
+:param json: The json object to update
+
+.. versionadded:: 3.8
 %End
 
   signals:
@@ -172,6 +205,9 @@ Constructor for QgsSymbolLegendNode.
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
 
 
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+
+
     virtual void setEmbeddedInParent( bool embedded );
 
 
@@ -358,6 +394,9 @@ Constructor for QgsImageLegendNode.
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
 
 
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+
+
 };
 
 class QgsRasterSymbolLegendNode : QgsLayerTreeModelLegendNode
@@ -389,6 +428,9 @@ Constructor for QgsRasterSymbolLegendNode.
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
 
 
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+
+
 };
 
 
@@ -419,6 +461,9 @@ Constructor for QgsWmsLegendNode.
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
 
 
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+
+
     virtual void invalidateMapBasedData();
 
 

python/core/auto_generated/qgslegendrenderer.sip.in

@@ -76,6 +76,13 @@ The ``painter`` should be scaled beforehand so that units correspond to millimet
 Draws the legend using a given render ``context``. The legend will occupy the area reported in legendSize().
 
 .. versionadded:: 3.6
+%End
+
+    void exportLegendToJson( const QgsRenderContext &context, QJsonObject &json );
+%Docstring
+Renders the legend in a ``json`` object.
+
+.. versionadded:: 3.8
 %End
 
     static void setNodeLegendStyle( QgsLayerTreeNode *node, QgsLegendStyle::Style style );

src/core/layertree/qgslayertreemodellegendnode.cpp

@@ -71,6 +71,11 @@ QgsLayerTreeModelLegendNode::ItemMetrics QgsLayerTreeModelLegendNode::draw( cons
   return im;
 }
 
+void QgsLayerTreeModelLegendNode::exportToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json )
+{
+  exportSymbolToJson( settings, context, json );
+  exportSymbolTextToJson( settings, json );
+}
 
 QSizeF QgsLayerTreeModelLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const
 {
@@ -84,6 +89,19 @@ QSizeF QgsLayerTreeModelLegendNode::drawSymbol( const QgsLegendSettings &setting
   return settings.symbolSize();
 }
 
+void QgsLayerTreeModelLegendNode::exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &, QJsonObject &json ) const
+{
+  const QIcon icon = data( Qt::DecorationRole ).value<QIcon>();
+  if ( icon.isNull() )
+    return;
+
+  const QImage image( icon.pixmap( settings.symbolSize().width(), settings.symbolSize().height() ).toImage() );
+  QByteArray byteArray;
+  QBuffer buffer( &byteArray );
+  image.save( &buffer, "PNG" );
+  const QString base64 = QString::fromLatin1( byteArray.toBase64().data() );
+  json[ "icon" ] = base64;
+}
 
 QSizeF QgsLayerTreeModelLegendNode::drawSymbolText( const QgsLegendSettings &settings, ItemContext *ctx, QSizeF symbolSize ) const
 {
@@ -129,6 +147,12 @@ QSizeF QgsLayerTreeModelLegendNode::drawSymbolText( const QgsLegendSettings &set
   return labelSize;
 }
 
+void QgsLayerTreeModelLegendNode::exportSymbolTextToJson( const QgsLegendSettings &, QJsonObject &json ) const
+{
+  const QString text = data( Qt::DisplayRole ).toString();
+  json[ "title" ] = text;
+}
+
 // -------------------------------------------------------------------------
 
 QgsSymbolLegendNode::QgsSymbolLegendNode( QgsLayerTreeLayer *nodeLayer, const QgsLegendSymbolItem &item, QObject *parent )
@@ -490,6 +514,47 @@ QSizeF QgsSymbolLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemC
                  std::max( height + 2 * heightOffset, static_cast< double >( settings.symbolSize().height() ) ) );
 }
 
+void QgsSymbolLegendNode::exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const
+{
+  const QgsSymbol *s = mItem.symbol();
+  if ( !s )
+  {
+    return;
+  }
+
+  QgsRenderContext ctx;
+  ctx.setScaleFactor( settings.dpi() / 25.4 );
+  ctx.setRendererScale( settings.mapScale() );
+  ctx.setMapToPixel( QgsMapToPixel( 1 / ( settings.mmPerMapUnit() * ctx.scaleFactor() ) ) );
+  ctx.setForceVectorOutput( true );
+
+  // ensure that a minimal expression context is available
+  QgsExpressionContext expContext = context.expressionContext();
+  expContext.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( nullptr ) );
+  ctx.setExpressionContext( expContext );
+
+  const QPixmap pix = QgsSymbolLayerUtils::symbolPreviewPixmap( mItem.symbol(), minimumIconSize(), 0, &ctx );
+  QImage img( pix.toImage().convertToFormat( QImage::Format_ARGB32_Premultiplied ) );
+
+  int opacity = 255;
+  if ( QgsVectorLayer *vectorLayer = dynamic_cast<QgsVectorLayer *>( layerNode()->layer() ) )
+    opacity = ( 255 * vectorLayer->opacity() );
+
+  if ( opacity != 255 )
+  {
+    QPainter painter;
+    painter.begin( &img );
+    painter.setCompositionMode( QPainter::CompositionMode_DestinationIn );
+    painter.fillRect( pix.rect(), QColor( 0, 0, 0, opacity ) );
+    painter.end();
+  }
+
+  QByteArray byteArray;
+  QBuffer buffer( &byteArray );
+  img.save( &buffer, "PNG" );
+  const QString base64 = QString::fromLatin1( byteArray.toBase64().data() );
+  json[ "icon" ] = base64;
+}
 
 void QgsSymbolLegendNode::setEmbeddedInParent( bool embedded )
 {
@@ -598,6 +663,15 @@ QSizeF QgsImageLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemCo
   return settings.wmsLegendSize();
 }
 
+void QgsImageLegendNode::exportSymbolToJson( const QgsLegendSettings &, const QgsRenderContext &, QJsonObject &json ) const
+{
+  QByteArray byteArray;
+  QBuffer buffer( &byteArray );
+  mImage.save( &buffer, "PNG" );
+  const QString base64 = QString::fromLatin1( byteArray.toBase64().data() );
+  json[ "icon" ] = base64;
+}
+
 // -------------------------------------------------------------------------
 
 QgsRasterSymbolLegendNode::QgsRasterSymbolLegendNode( QgsLayerTreeLayer *nodeLayer, const QColor &color, const QString &label, QObject *parent )
@@ -654,6 +728,44 @@ QSizeF QgsRasterSymbolLegendNode::drawSymbol( const QgsLegendSettings &settings,
   return settings.symbolSize();
 }
 
+void QgsRasterSymbolLegendNode::exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &, QJsonObject &json ) const
+{
+  QImage img = QImage( settings.symbolSize().toSize(), QImage::Format_ARGB32 );
+  img.fill( Qt::transparent );
+
+  QPainter painter( &img );
+  painter.setRenderHint( QPainter::Antialiasing );
+
+  QColor itemColor = mColor;
+  if ( QgsRasterLayer *rasterLayer = dynamic_cast<QgsRasterLayer *>( layerNode()->layer() ) )
+  {
+    if ( QgsRasterRenderer *rasterRenderer = rasterLayer->renderer() )
+      itemColor.setAlpha( rasterRenderer->opacity() * 255.0 );
+  }
+  painter.setBrush( itemColor );
+
+  if ( settings.drawRasterStroke() )
+  {
+    QPen pen;
+    pen.setColor( settings.rasterStrokeColor() );
+    pen.setWidthF( settings.rasterStrokeWidth() );
+    pen.setJoinStyle( Qt::MiterJoin );
+    painter.setPen( pen );
+  }
+  else
+  {
+    painter.setPen( Qt::NoPen );
+  }
+
+  painter.drawRect( QRectF( 0, 0, settings.symbolSize().width(), settings.symbolSize().height() ) );
+
+  QByteArray byteArray;
+  QBuffer buffer( &byteArray );
+  img.save( &buffer, "PNG" );
+  const QString base64 = QString::fromLatin1( byteArray.toBase64().data() );
+  json[ "icon" ] = base64;
+}
+
 // -------------------------------------------------------------------------
 
 QgsWmsLegendNode::QgsWmsLegendNode( QgsLayerTreeLayer *nodeLayer, QObject *parent )
@@ -722,6 +834,15 @@ QSizeF QgsWmsLegendNode::drawSymbol( const QgsLegendSettings &settings, ItemCont
   return settings.wmsLegendSize();
 }
 
+void QgsWmsLegendNode::exportSymbolToJson( const QgsLegendSettings &, const QgsRenderContext &, QJsonObject &json ) const
+{
+  QByteArray byteArray;
+  QBuffer buffer( &byteArray );
+  mImage.save( &buffer, "PNG" );
+  const QString base64 = QString::fromLatin1( byteArray.toBase64().data() );
+  json[ "icon" ] = base64;
+}
+
 /* private */
 QImage QgsWmsLegendNode::renderMessage( const QString &msg ) const
 {

src/core/layertree/qgslayertreemodellegendnode.h

@@ -110,6 +110,16 @@ class CORE_EXPORT QgsLayerTreeModelLegendNode : public QObject
      */
     virtual ItemMetrics draw( const QgsLegendSettings &settings, ItemContext *ctx );
 
+    /**
+     * Entry point called from QgsLegendRenderer to do the rendering in a
+     * JSON object.
+     * \param settings Legend layout configuration
+     * \param context Rendering context
+     * \param json The json object to update
+     * \since QGIS 3.8
+     */
+    void exportToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json );
+
     /**
      * Draws symbol on the left side of the item
      * \param settings Legend layout configuration
@@ -119,6 +129,15 @@ class CORE_EXPORT QgsLayerTreeModelLegendNode : public QObject
      */
     virtual QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const;
 
+    /**
+     * Adds a symbol in base64 string within a JSON object with the key "icon".
+     * \param settings Legend layout configuration
+     * \param context Rendering context
+     * \param json The json object to update
+     * \since QGIS 3.8
+     */
+    virtual void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const;
+
     /**
      * Draws label on the right side of the item
      * \param settings Legend layout configuration
@@ -128,6 +147,14 @@ class CORE_EXPORT QgsLayerTreeModelLegendNode : public QObject
      */
     virtual QSizeF drawSymbolText( const QgsLegendSettings &settings, ItemContext *ctx, QSizeF symbolSize ) const;
 
+    /**
+     * Adds a label in a JSON object with the key "title".
+     * \param settings Legend layout configuration
+     * \param json The json object to update
+     * \since QGIS 3.8
+     */
+    void exportSymbolTextToJson( const QgsLegendSettings &settings, QJsonObject &json ) const;
+
   signals:
     //! Emitted on internal data change so the layer tree model can forward the signal to views
     void dataChanged();
@@ -175,6 +202,8 @@ class CORE_EXPORT QgsSymbolLegendNode : public QgsLayerTreeModelLegendNode
 
     QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const override;
 
+    void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const override;
+
     void setEmbeddedInParent( bool embedded ) override;
 
     void setUserLabel( const QString &userLabel ) override { mUserLabel = userLabel; updateLabel(); }
@@ -354,6 +383,8 @@ class CORE_EXPORT QgsImageLegendNode : public QgsLayerTreeModelLegendNode
 
     QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const override;
 
+    void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const override;
+
   private:
     QImage mImage;
 };
@@ -383,6 +414,8 @@ class CORE_EXPORT QgsRasterSymbolLegendNode : public QgsLayerTreeModelLegendNode
 
     QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const override;
 
+    void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const override;
+
   private:
     QColor mColor;
     QString mLabel;
@@ -413,6 +446,8 @@ class CORE_EXPORT QgsWmsLegendNode : public QgsLayerTreeModelLegendNode
 
     QSizeF drawSymbol( const QgsLegendSettings &settings, ItemContext *ctx, double itemHeight ) const override;
 
+    void exportSymbolToJson( const QgsLegendSettings &settings, const QgsRenderContext &context, QJsonObject &json ) const override;
+
     void invalidateMapBasedData() override;
 
   private slots: