From: Carl Hetherington <cth@carlh.net>
Date: Sat, 21 Oct 2023 21:03:43 +0000 (+0200)
Subject: Support integer LUTs.
X-Git-Tag: v1.8.88~13
X-Git-Url: https://git.carlh.net/gitweb/?p=libdcp.git;a=commitdiff_plain;h=251f7a934525e0c846c95cc729664e95928e8aa5

Support integer LUTs.
---

diff --git a/src/transfer_function.cc b/src/transfer_function.cc
index be507af1..39c8db0a 100644
--- a/src/transfer_function.cc
+++ b/src/transfer_function.cc
@@ -53,23 +53,61 @@ vector<double> const&
 TransferFunction::double_lut(double from, double to, int bit_depth, bool inverse) const
 {
 	boost::mutex::scoped_lock lm (_mutex);
+	return double_lut_unlocked(from, to, bit_depth, inverse);
+}
+
+
+vector<double> const&
+TransferFunction::double_lut_unlocked(double from, double to, int bit_depth, bool inverse) const
+{
+	auto const descriptor = LUTDescriptor{from, to, bit_depth, inverse, 1};
+
+	auto i = _double_luts.find(descriptor);
+	if (i != _double_luts.end()) {
+		return i->second;
+	}
+
+	_double_luts[descriptor] = make_double_lut(from, to, bit_depth, inverse);
+	return _double_luts[descriptor];
+}
 
-	auto const descriptor = LUTDescriptor{from, to, bit_depth, inverse};
 
-	auto i = _luts.find(descriptor);
-	if (i != _luts.end()) {
+vector<int> const&
+TransferFunction::int_lut(double from, double to, int bit_depth, bool inverse, int scale) const
+{
+	boost::mutex::scoped_lock lm (_mutex);
+
+	auto const descriptor = LUTDescriptor{from, to, bit_depth, inverse, scale};
+
+	auto i = _int_luts.find(descriptor);
+	if (i != _int_luts.end()) {
 		return i->second;
 	}
 
-	_luts[descriptor] = make_double_lut(from, to, bit_depth, inverse);
-	return _luts[descriptor];
+	_int_luts[descriptor] = make_int_lut(from, to, bit_depth, inverse, scale);
+	return _int_luts[descriptor];
+}
+
+
+/* Caller must hold lock on _mutex */
+vector<int>
+TransferFunction::make_int_lut(double from, double to, int bit_depth, bool inverse, int scale) const
+{
+	auto source_lut = double_lut_unlocked(from, to, bit_depth, inverse);
+	auto const size = source_lut.size();
+	vector<int> lut(size);
+	for (size_t i = 0; i < size; ++i) {
+		lut[i] = lrint(source_lut[i] * scale);
+	}
+
+	return lut;
 }
 
 
 bool
 TransferFunction::LUTDescriptor::operator==(TransferFunction::LUTDescriptor const& other) const
 {
-	return from == other.from && to == other.to && bit_depth == other.bit_depth && inverse == other.inverse;
+	return from == other.from && to == other.to && bit_depth == other.bit_depth && inverse == other.inverse && scale == other.scale;
 }
 
 
@@ -79,6 +117,7 @@ TransferFunction::LUTDescriptorHasher::operator()(TransferFunction::LUTDescripto
 	return std::hash<double>()(desc.from) ^
 		std::hash<double>()(desc.to) ^
 		std::hash<int>()(desc.bit_depth) ^
-		std::hash<bool>()(desc.inverse);
+		std::hash<bool>()(desc.inverse) ^
+		std::hash<int>()(desc.scale);
 }
 
diff --git a/src/transfer_function.h b/src/transfer_function.h
index 033c3045..2340ebfd 100644
--- a/src/transfer_function.h
+++ b/src/transfer_function.h
@@ -62,6 +62,7 @@ public:
 
 	/** @return A look-up table (of size 2^bit_depth) */
 	std::vector<double> const& double_lut(double from, double to, int bit_depth, bool inverse) const;
+	std::vector<int> const& int_lut(double from, double to, int bit_depth, bool inverse, int scale) const;
 
 	virtual bool about_equal (std::shared_ptr<const TransferFunction> other, double epsilon) const = 0;
 
@@ -69,11 +70,15 @@ protected:
 	virtual std::vector<double> make_double_lut(double from, double to, int bit_depth, bool inverse) const = 0;
 
 private:
+	std::vector<int> make_int_lut(double from, double to, int bit_depth, bool inverse, int scale) const;
+	std::vector<double> const& double_lut_unlocked(double from, double to, int bit_depth, bool inverse) const;
+
 	struct LUTDescriptor {
 		double from;
 		double to;
 		int bit_depth;
 		bool inverse;
+		int scale;
 
 		bool operator==(LUTDescriptor const& other) const;
 	};
@@ -82,8 +87,9 @@ private:
 		std::size_t operator()(LUTDescriptor const& desc) const;
 	};
 
-	mutable std::unordered_map<LUTDescriptor, std::vector<double>, LUTDescriptorHasher> _luts;
-	/** mutex to protect _luts */
+	mutable std::unordered_map<LUTDescriptor, std::vector<double>, LUTDescriptorHasher> _double_luts;
+	mutable std::unordered_map<LUTDescriptor, std::vector<int>, LUTDescriptorHasher> _int_luts;
+	/** mutex to protect _double_luts and _int_luts */
 	mutable boost::mutex _mutex;
 };