Cine::Palette::saturatedAddNormalizedGray: Use fractional representation (dividend/denominator) of the normalized gray value in range [-1, +1] rather than a floating point.

svn-id: r39691

2 files changed, 17 insertions, 7 deletions

diff --git a/engines/cine/pal.cpp b/engines/cine/pal.cpp
index b2ce45ded8..f3031c3b60 100644
--- a/engines/cine/pal.cpp
+++ b/engines/cine/pal.cpp
@@ -257,12 +257,11 @@ Palette &Palette::saturatedAddColor(Palette& output, byte firstIndex, byte lastI
 	return output;
 }
 
-Palette &Palette::saturatedAddNormalizedGray(Palette& output, byte firstIndex, byte lastIndex, double normalizedGray) {
-	// Calculate the gray value rounded up away from zero
-	const double signedHalf = ((normalizedGray >= 0) ? +0.5 : -0.5);
-	const signed r = (signed)(_rMax * normalizedGray + signedHalf);
-	const signed g = (signed)(_gMax * normalizedGray + signedHalf);
-	const signed b = (signed)(_bMax * normalizedGray + signedHalf);
+Palette &Palette::saturatedAddNormalizedGray(Palette& output, byte firstIndex, byte lastIndex, int grayDividend, int grayDenominator) {
+	assert(grayDenominator != 0);
+	const signed r = _rMax * grayDividend / grayDenominator;
+	const signed g = _gMax * grayDividend / grayDenominator;
+	const signed b = _bMax * grayDividend / grayDenominator;
 
 	return saturatedAddColor(output, firstIndex, lastIndex, r, g, b);
 }
diff --git a/engines/cine/pal.h b/engines/cine/pal.h
index 2bb93245cf..3364f55857 100644
--- a/engines/cine/pal.h
+++ b/engines/cine/pal.h
@@ -116,7 +116,18 @@ public:
 
 	Palette &rotateRight(byte firstIndex, byte lastIndex);
 	Palette &saturatedAddColor(Palette& output, byte firstIndex, byte lastIndex, signed r, signed g, signed b);
-	Palette &saturatedAddNormalizedGray(Palette& output, byte firstIndex, byte lastIndex, double normalizedGray);
+
+	/*! \brief Saturated add a normalized gray value to current palette's subset and save the modified colors in the given output palette.
+	 * \param output The output palette (Only this palette is modified)
+	 * \param firstIndex First color index of the palette's subset (Inclusive range)
+	 * \param lastIndex Last color index of the palette's subset (Inclusive range)
+	 * \param grayDividend Dividend of the normalized gray value
+	 * \param grayDenominator Denominator of the normalized gray value
+	 * \note The normalized gray value (i.e. in range [-1, +1]) is given as a fractional number
+	 * (i.e. the normalized gray value is calculated by dividing grayDividend by grayDenominator).
+	 */
+	Palette &saturatedAddNormalizedGray(Palette& output, byte firstIndex, byte lastIndex, signed grayDividend, signed grayDenominator);
+
 	uint colorCount() const;
 
 	Palette &fillWithBlack();