Support Picture affected_by_tint flags

* Adds blend(Tone, Tone)
* Also fixes operator== for Tone to be non-member inline

src/game_picture.cpp

@@ -105,10 +105,15 @@ void Game_Picture::UpdateSprite() {
 		(int)(255 * (100 - data.current_bot_trans) / 100));
 	if (data.current_bot_trans != data.current_top_trans)
 		sprite->SetBushDepth(sprite->GetHeight() / 2);
-	sprite->SetTone(Tone((int) (data.current_red * 128 / 100),
-						 (int) (data.current_green * 128 / 100),
-						 (int) (data.current_blue * 128 / 100),
-						 (int) (data.current_sat * 128 / 100)));
+	auto tone = Tone((int) (data.current_red * 128 / 100),
+			(int) (data.current_green * 128 / 100),
+			(int) (data.current_blue * 128 / 100),
+			(int) (data.current_sat * 128 / 100));
+	if (data.flags.affected_by_tint) {
+		auto screen_tone = Main_Data::game_screen->GetTone();
+		tone = blend(tone, screen_tone);
+	}
+	sprite->SetTone(tone);
 }
 
 void Game_Picture::Show(const ShowParams& params) {

src/tone.cpp

@@ -33,14 +33,6 @@ Tone::Tone(int red, int green, int blue, int gray) :
 	gray(min(255, max(0, gray))) {
 }
 
-bool Tone::operator==(const Tone &other) const {
-	return red == other.red && green == other.green && blue == other.blue && gray == other.gray;
-}
-
-bool Tone::operator!=(const Tone &other) const {
-	return red != other.red || green != other.green || blue != other.blue || gray != other.gray;
-}
-
 void Tone::Set(int nred, int ngreen, int nblue, int ngray) {
 	red = min(255, max(0, nred));
 	green = min(255, max(0, ngreen));

src/tone.h

@@ -38,16 +38,6 @@ class Tone {
 	 */
 	Tone(int red, int green, int blue, int gray);
 
-	/**
-	 * Equality operator.
-	 */
-	bool operator==(const Tone &other) const;
-
-	/**
-	 * Inequality operator.
-	 */
-	bool operator!=(const Tone &other) const;
-
 	/**
 	 * Set all color properties.
 	 *
@@ -71,4 +61,23 @@ class Tone {
 	int gray;
 };
 
+inline Tone blend(const Tone& l, const Tone& r) {
+	return Tone((l.red + r.red) / 2,
+			(l.green + r.green) / 2,
+			(l.blue + r.blue) / 2,
+			(l.gray * r.gray) / 128);
+}
+
+inline bool operator==(const Tone &l, const Tone& r) {
+	return l.red == r.red
+		&& l.green == r.green
+		&& l.blue == r.blue
+		&& l.gray == r.gray;
+}
+
+inline bool operator!=(const Tone &l, const Tone& r) {
+	return !(l == r);
+}
+
+
 #endif