SCI: More work on kRemapColors

This implements some more color remap-based palette effects, found in QFG4

3 files changed, 34 insertions, 9 deletions

diff --git a/engines/sci/engine/kgraphics32.cpp b/engines/sci/engine/kgraphics32.cpp
index 685b3c0bd3..8b3afeef99 100644
--- a/engines/sci/engine/kgraphics32.cpp
+++ b/engines/sci/engine/kgraphics32.cpp
@@ -771,20 +771,23 @@ reg_t kRemapColors32(EngineState *s, int argc, reg_t *argv) {
 		}
 		break;
 	case 3:	{ // remap to gray
-		// Example call: QFG4 room 490 (Baba Yaga's hut) - params are color 253, 75% and 0
+		// Example call: QFG4 room 490 (Baba Yaga's hut) - params are color 253, 75% and 0.
+		// In this room, it's used for the cloud before Baba Yaga appears.
 		int16 color = argv[1].toSint16();
 		int16 percent = argv[2].toSint16(); // 0 - 100
-		uint16 unk3 = (argc >= 4) ? argv[3].toUint16() : 0;
-		warning("kRemapColors: RemapToGray color %d by %d percent (unk3 = %d)", color, percent, unk3);
-		// TODO
+		if (argc >= 4)
+			warning("RemapToGray called with 4 parameters, unknown parameter is %d", argv[3].toUint16());
+		g_sci->_gfxPalette->setRemappingPercentGray(color, percent);
 		}
 		break;
 	case 4:	{ // remap to percent gray
-		//int16 unk1 = argv[1].toSint16();
-		//uint16 unk2 = argv[2].toUint16();
-		//uint16 unk3 = argv[3].toUint16();
-		//uint16 unk4 = (argc >= 5) ? argv[4].toUint16() : 0;
-		kStub(s, argc, argv);
+		// Example call: QFG4 rooms 530/535 (swamp) - params are 253, 100%, 200
+		int16 color = argv[1].toSint16();
+		int16 percent = argv[2].toSint16(); // 0 - 100
+		// argv[3] is unknown (a number, e.g. 200) - start color, perhaps?
+		if (argc >= 5)
+			warning("RemapToGrayPercent called with 5 parameters, unknown parameter is %d", argv[4].toUint16());
+		g_sci->_gfxPalette->setRemappingPercentGray(color, percent);
 		}
 		break;
 	case 5:	{ // don't map to range
diff --git a/engines/sci/graphics/palette.cpp b/engines/sci/graphics/palette.cpp
index 68104b0ac8..53d69cdcca 100644
--- a/engines/sci/graphics/palette.cpp
+++ b/engines/sci/graphics/palette.cpp
@@ -375,6 +375,27 @@ void GfxPalette::setRemappingPercent(byte color, byte percent) {
 	_remappingType[color] = kRemappingByPercent;
 }
 
+void GfxPalette::setRemappingPercentGray(byte color, byte percent) {
+	_remapOn = true;
+
+	// We need to defer the setup of the remapping table every time the screen
+	// palette is changed, so that kernelFindColor() can find the correct
+	// colors. Set it once here, in case the palette stays the same and update
+	// it on each palette change by copySysPaletteToScreen().
+	_remappingPercentToSet = percent;
+
+	// Note: This is not what the original does, but the results are the same visually
+	for (int i = 0; i < 256; i++) {
+		byte rComponent = _sysPalette.colors[i].r * _remappingPercentToSet * 0.30 / 100;
+		byte gComponent = _sysPalette.colors[i].g * _remappingPercentToSet * 0.59 / 100;
+		byte bComponent = _sysPalette.colors[i].b * _remappingPercentToSet * 0.11 / 100;
+		byte luminosity = rComponent + gComponent + bComponent;
+		_remappingByPercent[i] = kernelFindColor(luminosity, luminosity, luminosity);
+	}
+
+	_remappingType[color] = kRemappingByPercent;
+}
+
 void GfxPalette::setRemappingRange(byte color, byte from, byte to, byte base) {
 	_remapOn = true;
 
diff --git a/engines/sci/graphics/palette.h b/engines/sci/graphics/palette.h
index 9898315897..e974781d49 100644
--- a/engines/sci/graphics/palette.h
+++ b/engines/sci/graphics/palette.h
@@ -61,6 +61,7 @@ public:
 
 	void resetRemapping();
 	void setRemappingPercent(byte color, byte percent);
+	void setRemappingPercentGray(byte color, byte percent);
 	void setRemappingRange(byte color, byte from, byte to, byte base);
 	bool isRemapped(byte color) const {
 		return _remapOn && (_remappingType[color] != kRemappingNone);