Aerofoil/PortabilityLayer/AntiAliasTable.cpp

#include "AntiAliasTable.h"
#include "RGBAColor.h"

#include <algorithm>
#include <math.h>

// TODO: This is not gamma correct...
namespace PortabilityLayer
{
#if 0
	void AntiAliasTable::GenerateForPalette(const RGBAColor &baseColorRef, const RGBAColor *colors, size_t numColors)
	{
		const RGBAColor baseColor = baseColorRef;

		if (numColors > 256)
			numColors = 256;

		unsigned int baseCh[3] = { baseColor.r, baseColor.g, baseColor.b };

		for (size_t i = 0; i < numColors; i++)
		{
			const RGBAColor existingColor = colors[i];

			unsigned int existingCh[3] = { existingColor.r, existingColor.g, existingColor.b };

			// 0 alpha is always the same color
			m_aaTranslate[i][0] = static_cast<uint8_t>(i);

			for (unsigned int b = 1; b < 16; b++)
			{
				unsigned int newCh[3];

				for (unsigned int ch = 0; ch < 3; ch++)
					newCh[ch] = (15 - b) * existingCh[ch] + b * baseCh[ch];

				uint32_t bestError = 0xffffffffU;
				size_t bestColor = 0;
				for (size_t cmp = 0; cmp < numColors; cmp++)
				{
					int16_t existingChScaled[3] = { colors[cmp].r * 15, colors[cmp].g * 15, colors[cmp].b * 15 };

					uint32_t error = 0;
					for (unsigned int ch = 0; ch < 3; ch++)
					{
						int16_t delta = static_cast<int16_t>(newCh[ch]) - existingChScaled[ch];
						error += static_cast<uint32_t>(delta * delta);
					}

					if (error < bestError)
					{
						bestError = error;
						bestColor = cmp;
					}
				}

				m_aaTranslate[i][b] = static_cast<uint8_t>(bestColor);
			}
		}
	}
#else
	void AntiAliasTable::GenerateForPalette(const RGBAColor &baseColorRef, const RGBAColor *colors, size_t numColors)
	{
		const RGBAColor baseColor = baseColorRef;

		if (numColors > 256)
			numColors = 256;

		unsigned int baseCh[3] = { baseColor.r, baseColor.g, baseColor.b };
		unsigned int baseChLinear[3];

		for (int i = 0; i < 3; i++)
			baseChLinear[i] = baseCh[i] * baseCh[i];

		for (size_t i = 0; i < numColors; i++)
		{
			const RGBAColor existingColor = colors[i];

			unsigned int existingCh[3] = { existingColor.r, existingColor.g, existingColor.b };
			unsigned int existingChLinear[3];

			for (int i = 0; i < 3; i++)
				existingChLinear[i] = existingCh[i] * existingCh[i];

			// 0 alpha is always the same color
			m_aaTranslate[i][0] = static_cast<uint8_t>(i);

			for (unsigned int b = 1; b < 16; b++)
			{
				uint32_t newChLinear[3];

				for (unsigned int ch = 0; ch < 3; ch++)
					newChLinear[ch] = (15 - b) * existingChLinear[ch] + b * baseChLinear[ch];

				uint64_t bestError = UINT64_MAX;
				size_t bestColor = 0;
				for (size_t cmp = 0; cmp < numColors; cmp++)
				{
					int32_t compareColor[3] = { colors[cmp].r, colors[cmp].g, colors[cmp].b };
					for (unsigned int ch = 0; ch < 3; ch++)
					{
						compareColor[ch] = compareColor[ch] * compareColor[ch] * 15;
					}

					uint64_t error = 0;
					for (unsigned int ch = 0; ch < 3; ch++)
					{
						int64_t delta = static_cast<int32_t>(newChLinear[ch]) - compareColor[ch];
						error += static_cast<uint64_t>(delta * delta);
					}

					if (error < bestError)
					{
						bestError = error;
						bestColor = cmp;
					}
				}

				m_aaTranslate[i][b] = static_cast<uint8_t>(bestColor);
			}
		}
	}

	void AntiAliasTable::GenerateForSimpleScale(uint8_t colorChannel)
	{
		const double gamma = 1.8;
		const double rcpGamma = 1.0 / gamma;
		const double rcp255 = 1.0 / 255.0;
		const double rcp15 = 1.0 / 15.0;
		double colorChannelLinear = pow(colorChannel * rcp255, gamma);

		for (size_t baseColor = 0; baseColor < 256; baseColor++)
		{
			const double baseColorLinear = pow(baseColor * rcp255, gamma);

			for (size_t opacity = 0; opacity < 16; opacity++)
			{
				const double opacityF = static_cast<double>(opacity) * rcp15;
				const double blendedColor = colorChannelLinear * opacityF + (1.0 - opacityF) * baseColorLinear;

				const double blendedColorGammaSpace = pow(std::min(std::max(0.0, blendedColor), 1.0), rcpGamma);

				m_aaTranslate[baseColor][opacity] = static_cast<uint8_t>(floor(blendedColorGammaSpace * 255.0 + 0.5));
			}
		}
	}
#endif
}