ADD: Only apply cgcompress:alpha-replace when needed #5

src/Image.cpp

@@ -411,3 +411,19 @@ Image Image::optimize_filesize( Format format ) const{
 		return copy.remove_transparent();
 }
 
+bool Image::mustKeepAlpha() const{
+	auto img = qimg();
+	int width = img.width(), height = img.height();
+
+	for( int iy=0; iy<height; iy++ ){
+		auto out = (const QRgb*)img.constScanLine( iy );
+
+		for( int ix=0; ix<width; ix++ ){
+			auto pixel = out[ix];
+			if( (qAlpha(pixel) != 255) && (pixel != TRANS_SET) )
+				return true;
+		}
+	}
+
+	return false;
+}

src/Image.hpp

@@ -127,6 +127,8 @@ class Image {
 		bool operator==( const Image& other ) const{
 			return pos == other.pos && img == other.img;
 		}
+
+		bool mustKeepAlpha() const;
 };
 
 #endif

src/OraSaver.cpp

@@ -142,9 +142,19 @@ void OraSaver::save( QString path, Format format ) const{
 		stack += "<stack>";
 
 		for( auto layer : boost::adaptors::reverse(frame.layers) ){
+			//Detect composition mode
+			//TODO: Decide this earlier and change encoding type
+			QString composition = "composite-op=\"cgcompress:alpha-replace\"";
+			if( !primitives[layer].mustKeepAlpha() )
+				composition = "";
+
 			QString name = QString( "data/%1.%2" ).arg( layer ).arg( format.ext() );
-			stack += QString( "<layer composite-op=\"cgcompress:alpha-replace\" name=\"%1\" src=\"%1\" x=\"%2\" y=\"%3\" />" )
-				.arg( name ).arg( primitives[layer].get_pos().x() ).arg( primitives[layer].get_pos().y() );
+			stack += QString( "<layer %1 name=\"%2\" src=\"%2\" x=\"%3\" y=\"%4\" />" )
+				.arg( composition )
+				.arg( name )
+				.arg( primitives[layer].get_pos().x() )
+				.arg( primitives[layer].get_pos().y() )
+				;
 		}
 
 		stack += "</stack>";