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sonic3air-main/Oxygen/oxygenengine/source/oxygen/rendering/software/SoftwareBlur.h

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+/*
+*	Part of the Oxygen Engine / Sonic 3 A.I.R. software distribution.
+*	Copyright (C) 2017-2024 by Eukaryot
+*
+*	Published under the GNU GPLv3 open source software license, see license.txt
+*	or https://www.gnu.org/licenses/gpl-3.0.en.html
+*/
+
+#pragma once
+
+#include <rmxbase.h>
+
+
+struct SoftwareBlur
+{
+public:
+	static void blurBitmap(Bitmap& bitmap, int blurValue)
+	{
+		switch (blurValue)
+		{
+			case 1:  blurBitmap<16>(bitmap);  break;
+			case 2:  blurBitmap<32>(bitmap);  break;
+			case 3:  blurBitmap<48>(bitmap);  break;
+			case 4:  blurBitmap<64>(bitmap);  break;
+			default: break;
+		}
+	}
+
+private:
+	// Template parameters are weights for each of the neighbor pixels, as a fraction of 256;
+	//  the higher these values are, the stronger the blur gets
+	template<int weightX, int weightY = weightX>
+	static void blurBitmap(Bitmap& bitmap)
+	{
+		// Can't blur bitmaps that are too small
+		if (bitmap.getWidth() < 2 || bitmap.getHeight() < 2)
+			return;
+
+		// Get weights for the central pixel
+		constexpr int invWeightX = 256 - weightX * 2;
+		constexpr int invWeightY = 256 - weightY * 2;
+
+		mTemp.create(bitmap.getSize());
+
+		// Pass 1: Blur in x-direction
+		for (int y = 0; y < bitmap.getHeight(); ++y)
+		{
+			uint32* dst = mTemp.getPixelPointer(0, y);
+			const uint32* src = bitmap.getPixelPointer(0, y);
+
+			// Preparations & leftmost pixel
+			uint32 src0 = src[0];
+			uint32 src1 = src[0];
+			uint32 src2 = src[1];
+			dst[0] = mixColors<weightX, invWeightX>(src0, src1, src2);
+
+			// Pixels in between
+			const uint32* end = src + ((std::ptrdiff_t)bitmap.getWidth() - 2);
+			while (src != end)
+			{
+				++src;
+				++dst;
+				src0 = src1;
+				src1 = src2;
+				src2 = src[1];
+				dst[0] = mixColors<weightX, invWeightX>(src0, src1, src2);
+			}
+
+			// Rightmost pixel
+			dst[1] = mixColors<weightX, invWeightX>(src1, src2, src2);
+		}
+
+		// Copy everything over
+		bitmap = mTemp;
+
+		// Pass 2: Blur in y-direction
+		{
+			// Topmost line
+			mixLines<weightY, invWeightY>(bitmap, mTemp, 0, 0, 1);
+
+			// Lines in between
+			int y = 1;
+			for (; y < bitmap.getHeight() - 1; ++y)
+			{
+				mixLines<weightY, invWeightY>(bitmap, mTemp, y-1, y, y+1);
+			}
+
+			// Bottommost line
+			mixLines<weightY, invWeightY>(bitmap, mTemp, y-1, y, y);
+		}
+	}
+
+private:
+	template<int factor0, int factor1>
+	static inline uint32 mixColors(uint32 src0, uint32 src1, uint32 src2)
+	{
+		return ((((src0 & 0xff00ff) * factor0 + (src1 & 0xff00ff) * factor1 + (src2 & 0xff00ff) * factor0) >> 8) & 0xff00ff)
+			 + ((((src0 & 0x00ff00) * factor0 + (src1 & 0x00ff00) * factor1 + (src2 & 0x00ff00) * factor0) >> 8) & 0x00ff00);
+	};
+
+	template<int factor0, int factor1>
+	static inline void mixLines(Bitmap& output, const Bitmap& input, int y0, int y1, int y2)
+	{
+		const uint32* src0 = input.getPixelPointer(0, y0);
+		uint32* src1 = output.getPixelPointer(0, y1);
+		const uint32* src2 = input.getPixelPointer(0, y2);
+
+		uint32* end = src1 + input.getWidth();
+		for (; src1 != end; ++src0, ++src1, ++src2)
+		{
+			*src1 = mixColors<factor0, factor1>(*src0, *src1, *src2);
+		}
+	}
+
+private:
+	static inline Bitmap mTemp;
+};