TITANIC: Fix blitting of game objects with a transparency surface

1 files changed, 24 insertions, 11 deletions

diff --git a/engines/titanic/support/transparency_surface.cpp b/engines/titanic/support/transparency_surface.cpp
index 8b5cbecc5f..505cd1ff6c 100644
--- a/engines/titanic/support/transparency_surface.cpp
+++ b/engines/titanic/support/transparency_surface.cpp
@@ -31,24 +31,25 @@ CTransparencySurface::CTransparencySurface(const Graphics::Surface *surface,
 	_pitch = 0;
 	_runLength = 0;
 	_flag = false;
-	_flag1 = false;
-	_flag2 = true;
+	_opaqueColor = 0;
+	_transparentColor = 0xff;
 
 	switch (transMode) {
 	case TRANS_MASK0:
 	case TRANS_ALPHA0:
-		_flag2 = false;
-		_flag1 = true;
+		_transparentColor = 0;
+		_opaqueColor = 0xff;
 		break;
 	case TRANS_MASK255:
 	case TRANS_ALPHA255:
-		_flag2 = true;
-		_flag1 = false;
+		_transparentColor = 0xff;
+		_opaqueColor = 0;
 		break;
 	case TRANS_DEFAULT:
+		// If top left pixel is low, then 0 is the transparent color
 		if (*(const byte *)surface->getPixels() < 0x80) {
-			_flag1 = true;
-			_flag2 = false;
+			_opaqueColor = 0xff;
+			_transparentColor = 0;
 		}
 		break;
 	default:
@@ -72,11 +73,23 @@ uint CTransparencySurface::getPixel() const {
 
 uint CTransparencySurface::getAlpha() const {
 	byte pixel = getPixel();
-	return _flag1 ? 0xFF - pixel : pixel;
+	return _opaqueColor ? 0xFF - pixel : pixel;
 }
 
-bool CTransparencySurface::isPixelTransparent() {
-	return getAlpha() == 0xff;
+bool CTransparencySurface::isPixelOpaque() const {
+	byte pixel = getPixel();
+	if (_opaqueColor)
+		return pixel >= 0xf0;
+	else
+		return pixel < 0x10;
+}
+
+bool CTransparencySurface::isPixelTransparent() const {
+	byte pixel = getPixel();
+	if (_transparentColor)
+		return pixel >= 0xf0;
+	else
+		return pixel < 0x10;
 }
 
 } // End of namespace Titanic