[FEATURE] color_grayscale_average() and color_mix_rgb() expression functions (#6554)

nirvn · web-flow · commit b42c893bbcf1 · 2018-03-07T11:59:52.000+07:00
diff --git a/resources/function_help/json/color_grayscale_average b/resources/function_help/json/color_grayscale_average
@@ -0,0 +1,9 @@
+{
+  "name": "color_grayscale_average",
+  "type": "function",
+  "description": "Applies a grayscale filter and returns a string representation from a provided color.",
+  "arguments": [
+               {"arg":"color", "description":"a color string"}
+	          ],
+  "examples": [ { "expression":"color_grayscale_average('255,100,50')", "returns":"127,127,127,255"}]
+}
diff --git a/resources/function_help/json/color_mix_rgb b/resources/function_help/json/color_mix_rgb
@@ -0,0 +1,11 @@
+{
+  "name": "color_mix_rgb",
+  "type": "function",
+  "description": "Returns a string representing a color mixing the reg, green, blue, and alpha values of two provided colors based on a given ratio.",
+  "arguments": [
+               {"arg":"color1", "description":"a color string"},
+               {"arg":"color2", "description":"a color string"},
+               {"arg":"ratio", "description":"a ratio"}
+	          ],
+  "examples": [ { "expression":"color_mix_rgb('0,0,0','255,255,255',0.5)", "returns":"127,127,127,255"}]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -2998,6 +2998,41 @@ static QVariant fcnFormatDate( const QVariantList &values, const QgsExpressionCo
   return dt.toString( format );
 }
 
+static QVariant fcnColorGrayscaleAverage( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * )
+{
+  QColor color = QgsSymbolLayerUtils::decodeColor( values.at( 0 ).toString() );
+  int avg = ( color.red() + color.green() + color.blue() ) / 3;
+  int alpha = color.alpha();
+
+  color.setRgb( avg, avg, avg, alpha );
+
+  return QgsSymbolLayerUtils::encodeColor( color );
+}
+
+static QVariant fcnColorMixRgb( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  QColor color1 = QgsSymbolLayerUtils::decodeColor( values.at( 0 ).toString() );
+  QColor color2 = QgsSymbolLayerUtils::decodeColor( values.at( 1 ).toString() );
+  double ratio = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
+  if ( ratio > 1 )
+  {
+    ratio = 1;
+  }
+  else if ( ratio < 0 )
+  {
+    ratio = 0;
+  }
+
+  int red = color1.red() * ( 1 - ratio ) + color2.red() * ratio;
+  int green = color1.green() * ( 1 - ratio ) + color2.green() * ratio;
+  int blue = color1.blue() * ( 1 - ratio ) + color2.blue() * ratio;
+  int alpha = color1.alpha() * ( 1 - ratio ) + color2.alpha() * ratio;
+
+  QColor newColor( red, green, blue, alpha );
+
+  return QgsSymbolLayerUtils::encodeColor( newColor );
+}
+
 static QVariant fcnColorRgb( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   int red = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
@@ -4098,6 +4133,8 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "format" ), -1, fcnFormatString, QStringLiteral( "String" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "format_number" ), 2, fcnFormatNumber, QStringLiteral( "String" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "format_date" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "date" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "format" ) ), fcnFormatDate, QStringList() << QStringLiteral( "String" ) << QStringLiteral( "Date and Time" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "color_grayscale_average" ), 1, fcnColorGrayscaleAverage, QStringLiteral( "Color" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "color_mix_rgb" ), 3, fcnColorMixRgb, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "color_rgb" ), 3, fcnColorRgb, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "color_rgba" ), 4, fncColorRgba, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "ramp_color" ), 2, fcnRampColor, QStringLiteral( "Color" ) )
diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
@@ -1109,6 +1109,8 @@ class TestQgsExpression: public QObject
       QTest::newRow( "color hsva" ) << "color_hsva(40,100,100,200)" << false << QVariant( "255,170,0,200" );
       QTest::newRow( "color cmyk" ) << "color_cmyk(100,50,33,10)" << false << QVariant( "0,115,154" );
       QTest::newRow( "color cmyka" ) << "color_cmyka(50,25,90,60,200)" << false << QVariant( "51,76,10,200" );
+      QTest::newRow( "color grayscale average" ) << "color_grayscale_average('255,100,50')" << false << QVariant( "135,135,135,255" );
+      QTest::newRow( "color mix rgb" ) << "color_mix_rgb('0,0,0,100','255,255,255',0.5)" << false << QVariant( "127,127,127,177" );
 
       QTest::newRow( "color part bad color" ) << "color_part('notacolor','red')" << true << QVariant();
       QTest::newRow( "color part bad part" ) << "color_part(color_rgb(255,127,0),'bad')" << true << QVariant();
