Add ETC1/ETC2 compression support though etc2comp.

Remove rg-etc1 code. Also updated travis to use ubuntu 14.04.

Fixes #8457.

1 files changed, 1281 insertions, 0 deletions

diff --git a/thirdparty/etc2comp/EtcBlock4x4Encoding_ETC1.cpp b/thirdparty/etc2comp/EtcBlock4x4Encoding_ETC1.cpp
new file mode 100644
index 0000000000..a27f74c0d5
--- /dev/null
+++ b/thirdparty/etc2comp/EtcBlock4x4Encoding_ETC1.cpp
@@ -0,0 +1,1281 @@
+/*
+ * Copyright 2015 The Etc2Comp Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+EtcBlock4x4Encoding_ETC1.cpp
+
+Block4x4Encoding_ETC1 is the encoder to use when targetting file format ETC1.  This encoder is also
+used for the ETC1 subset of file format RGB8, RGBA8 and RGB8A1
+
+*/
+
+#include "EtcConfig.h"
+#include "EtcBlock4x4Encoding_ETC1.h"
+
+#include "EtcBlock4x4.h"
+#include "EtcBlock4x4EncodingBits.h"
+#include "EtcDifferentialTrys.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <float.h>
+#include <limits>
+
+namespace Etc
+{
+
+	// pixel processing order if the flip bit = 0 (horizontal split)
+	const unsigned int Block4x4Encoding_ETC1::s_auiPixelOrderFlip0[PIXELS] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
+
+	// pixel processing order if the flip bit = 1 (vertical split)
+	const unsigned int Block4x4Encoding_ETC1::s_auiPixelOrderFlip1[PIXELS] = { 0, 1, 4, 5, 8, 9, 12, 13, 2, 3, 6, 7, 10, 11, 14, 15 };
+
+	// pixel processing order for horizontal scan (ETC normally does a vertical scan)
+	const unsigned int Block4x4Encoding_ETC1::s_auiPixelOrderHScan[PIXELS] = { 0, 4, 8, 12, 1, 5, 9, 13, 2, 6, 10, 14, 3, 7, 11, 15 };
+
+	// pixel indices for different block halves
+	const unsigned int Block4x4Encoding_ETC1::s_auiLeftPixelMapping[8] = { 0, 1, 2, 3, 4, 5, 6, 7 };
+	const unsigned int Block4x4Encoding_ETC1::s_auiRightPixelMapping[8] = { 8, 9, 10, 11, 12, 13, 14, 15 };
+	const unsigned int Block4x4Encoding_ETC1::s_auiTopPixelMapping[8] = { 0, 1, 4, 5, 8, 9, 12, 13 };
+	const unsigned int Block4x4Encoding_ETC1::s_auiBottomPixelMapping[8] = { 2, 3, 6, 7, 10, 11, 14, 15 };
+
+	// CW ranges that the ETC1 decoders use
+	// CW is basically a contrast for the different selector bits, since these values are offsets to the base color
+	// the first axis in the array is indexed by the CW in the encoding bits
+	// the second axis in the array is indexed by the selector bits
+	float Block4x4Encoding_ETC1::s_aafCwTable[CW_RANGES][SELECTORS] =
+	{
+		{ 2.0f / 255.0f, 8.0f / 255.0f, -2.0f / 255.0f, -8.0f / 255.0f },
+		{ 5.0f / 255.0f, 17.0f / 255.0f, -5.0f / 255.0f, -17.0f / 255.0f },
+		{ 9.0f / 255.0f, 29.0f / 255.0f, -9.0f / 255.0f, -29.0f / 255.0f },
+		{ 13.0f / 255.0f, 42.0f / 255.0f, -13.0f / 255.0f, -42.0f / 255.0f },
+		{ 18.0f / 255.0f, 60.0f / 255.0f, -18.0f / 255.0f, -60.0f / 255.0f },
+		{ 24.0f / 255.0f, 80.0f / 255.0f, -24.0f / 255.0f, -80.0f / 255.0f },
+		{ 33.0f / 255.0f, 106.0f / 255.0f, -33.0f / 255.0f, -106.0f / 255.0f },
+		{ 47.0f / 255.0f, 183.0f / 255.0f, -47.0f / 255.0f, -183.0f / 255.0f }
+	};
+
+	// ----------------------------------------------------------------------------------------------------
+	//
+	Block4x4Encoding_ETC1::Block4x4Encoding_ETC1(void)
+	{
+		m_mode = MODE_ETC1;
+		m_boolDiff = false;
+		m_boolFlip = false;
+		m_frgbaColor1 = ColorFloatRGBA();
+		m_frgbaColor2 = ColorFloatRGBA();
+		m_uiCW1 = 0;
+		m_uiCW2 = 0;
+		for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+		{
+			m_auiSelectors[uiPixel] = 0;
+			m_afDecodedAlphas[uiPixel] = 1.0f;
+		}
+
+		m_boolMostLikelyFlip = false;
+
+		m_fError = -1.0f;
+
+		m_fError1 = -1.0f;
+		m_fError2 = -1.0f;
+		m_boolSeverelyBentDifferentialColors = false;
+
+		for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+		{
+			m_afDecodedAlphas[uiPixel] = 1.0f;
+		}
+
+	}
+
+	 Block4x4Encoding_ETC1::~Block4x4Encoding_ETC1(void) {}
+
+	// ----------------------------------------------------------------------------------------------------
+	// initialization prior to encoding
+	// a_pblockParent points to the block associated with this encoding
+	// a_errormetric is used to choose the best encoding
+	// a_pafrgbaSource points to a 4x4 block subset of the source image
+	// a_paucEncodingBits points to the final encoding bits
+	//
+	void Block4x4Encoding_ETC1::InitFromSource(Block4x4 *a_pblockParent,
+												ColorFloatRGBA *a_pafrgbaSource,
+												unsigned char *a_paucEncodingBits, ErrorMetric a_errormetric)
+	{
+
+		Block4x4Encoding::Init(a_pblockParent, a_pafrgbaSource,a_errormetric);
+
+		for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+		{
+			m_afDecodedAlphas[uiPixel] = 1.0f;
+		}
+
+		m_fError = -1.0f;
+
+		m_pencodingbitsRGB8 = (Block4x4EncodingBits_RGB8 *)(a_paucEncodingBits);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// initialization from the encoding bits of a previous encoding
+	// a_pblockParent points to the block associated with this encoding
+	// a_errormetric is used to choose the best encoding
+	// a_pafrgbaSource points to a 4x4 block subset of the source image
+	// a_paucEncodingBits points to the final encoding bits of a previous encoding
+	//
+	void Block4x4Encoding_ETC1::InitFromEncodingBits(Block4x4 *a_pblockParent,
+														unsigned char *a_paucEncodingBits,
+														ColorFloatRGBA *a_pafrgbaSource, 
+														ErrorMetric a_errormetric)
+	{
+
+		Block4x4Encoding::Init(a_pblockParent, a_pafrgbaSource,a_errormetric);
+		m_fError = -1.0f;
+
+		m_pencodingbitsRGB8 = (Block4x4EncodingBits_RGB8 *)a_paucEncodingBits;
+
+		m_mode = MODE_ETC1;
+		m_boolDiff = m_pencodingbitsRGB8->individual.diff;
+		m_boolFlip = m_pencodingbitsRGB8->individual.flip;
+		if (m_boolDiff)
+		{
+			int iR2 = (int)(m_pencodingbitsRGB8->differential.red1 + m_pencodingbitsRGB8->differential.dred2);
+			if (iR2 < 0)
+			{
+				iR2 = 0;
+			}
+			else if (iR2 > 31)
+			{
+				iR2 = 31;
+			}
+
+			int iG2 = (int)(m_pencodingbitsRGB8->differential.green1 + m_pencodingbitsRGB8->differential.dgreen2);
+			if (iG2 < 0)
+			{
+				iG2 = 0;
+			}
+			else if (iG2 > 31)
+			{
+				iG2 = 31;
+			}
+
+			int iB2 = (int)(m_pencodingbitsRGB8->differential.blue1 + m_pencodingbitsRGB8->differential.dblue2);
+			if (iB2 < 0)
+			{
+				iB2 = 0;
+			}
+			else if (iB2 > 31)
+			{
+				iB2 = 31;
+			}
+
+			m_frgbaColor1 = ColorFloatRGBA::ConvertFromRGB5(m_pencodingbitsRGB8->differential.red1, m_pencodingbitsRGB8->differential.green1, m_pencodingbitsRGB8->differential.blue1);
+			m_frgbaColor2 = ColorFloatRGBA::ConvertFromRGB5((unsigned char)iR2, (unsigned char)iG2, (unsigned char)iB2);
+
+		}
+		else
+		{
+			m_frgbaColor1 = ColorFloatRGBA::ConvertFromRGB4(m_pencodingbitsRGB8->individual.red1, m_pencodingbitsRGB8->individual.green1, m_pencodingbitsRGB8->individual.blue1);
+			m_frgbaColor2 = ColorFloatRGBA::ConvertFromRGB4(m_pencodingbitsRGB8->individual.red2, m_pencodingbitsRGB8->individual.green2, m_pencodingbitsRGB8->individual.blue2);
+		}
+
+		m_uiCW1 = m_pencodingbitsRGB8->individual.cw1;
+		m_uiCW2 = m_pencodingbitsRGB8->individual.cw2;
+
+		InitFromEncodingBits_Selectors();
+
+		Decode();
+
+		CalcBlockError();
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// init the selectors from a prior encoding
+	//
+	void Block4x4Encoding_ETC1::InitFromEncodingBits_Selectors(void)
+	{
+
+		unsigned char *paucSelectors = (unsigned char *)&m_pencodingbitsRGB8->individual.selectors;
+
+		for (unsigned int iPixel = 0; iPixel < PIXELS; iPixel++)
+		{
+			unsigned int uiByteMSB = (unsigned int)(1 - (iPixel / 8));
+			unsigned int uiByteLSB = (unsigned int)(3 - (iPixel / 8));
+			unsigned int uiShift = (unsigned int)(iPixel & 7);
+
+			unsigned int uiSelectorMSB = (unsigned int)((paucSelectors[uiByteMSB] >> uiShift) & 1);
+			unsigned int uiSelectorLSB = (unsigned int)((paucSelectors[uiByteLSB] >> uiShift) & 1);
+
+			m_auiSelectors[iPixel] = (uiSelectorMSB << 1) + uiSelectorLSB;
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// perform a single encoding iteration
+	// replace the encoding if a better encoding was found
+	// subsequent iterations generally take longer for each iteration
+	// set m_boolDone if encoding is perfect or encoding is finished based on a_fEffort
+	//
+	void Block4x4Encoding_ETC1::PerformIteration(float a_fEffort)
+	{
+		assert(!m_boolDone);
+
+		switch (m_uiEncodingIterations)
+		{
+		case 0:
+			PerformFirstIteration();
+			break;
+
+		case 1:
+			TryDifferential(m_boolMostLikelyFlip, 1, 0, 0);
+			break;
+
+		case 2:
+			TryIndividual(m_boolMostLikelyFlip, 1);
+			if (a_fEffort <= 49.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 3:
+			TryDifferential(!m_boolMostLikelyFlip, 1, 0, 0);
+			if (a_fEffort <= 59.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 4:
+			TryIndividual(!m_boolMostLikelyFlip, 1);
+			if (a_fEffort <= 69.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 5:
+			TryDegenerates1();
+			if (a_fEffort <= 79.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 6:
+			TryDegenerates2();
+			if (a_fEffort <= 89.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 7:
+			TryDegenerates3();
+			if (a_fEffort <= 99.5f)
+			{
+				m_boolDone = true;
+			}
+			break;
+
+		case 8:
+			TryDegenerates4();
+			m_boolDone = true;
+			break;
+
+		default:
+			assert(0);
+			break;
+		}
+
+		m_uiEncodingIterations++;
+		SetDoneIfPerfect();
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// find best initial encoding to ensure block has a valid encoding
+	//
+	void Block4x4Encoding_ETC1::PerformFirstIteration(void)
+	{
+		CalculateMostLikelyFlip();
+
+		m_fError = FLT_MAX;
+
+		TryDifferential(m_boolMostLikelyFlip, 0, 0, 0);
+		SetDoneIfPerfect();
+		if (m_boolDone)
+		{
+			return;
+		}
+
+		TryIndividual(m_boolMostLikelyFlip, 0);
+		SetDoneIfPerfect();
+		if (m_boolDone)
+		{
+			return;
+		}
+		TryDifferential(!m_boolMostLikelyFlip, 0, 0, 0);
+		SetDoneIfPerfect();
+		if (m_boolDone)
+		{
+			return;
+		}
+		TryIndividual(!m_boolMostLikelyFlip, 0);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// algorithm:
+	// create a source average color for the Left, Right, Top and Bottom halves using the 8 pixels in each half
+	// note: the "gray line" is the line of equal delta RGB that goes thru the average color
+	// for each half:
+	//		see how close each of the 8 pixels are to the "gray line" that goes thru the source average color
+	//		create an error value that is the sum of the distances from the gray line
+	// h_error is the sum of Left and Right errors
+	// v_error is the sum of Top and Bottom errors
+	//
+	void Block4x4Encoding_ETC1::CalculateMostLikelyFlip(void)
+	{
+		static const bool DEBUG_PRINT = false;
+
+		CalculateSourceAverages();
+
+		float fLeftGrayErrorSum = 0.0f;
+		float fRightGrayErrorSum = 0.0f;
+		float fTopGrayErrorSum = 0.0f;
+		float fBottomGrayErrorSum = 0.0f;
+
+		for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+		{
+			ColorFloatRGBA *pfrgbaLeft = &m_pafrgbaSource[uiPixel];
+			ColorFloatRGBA *pfrgbaRight = &m_pafrgbaSource[uiPixel + 8];
+			ColorFloatRGBA *pfrgbaTop = &m_pafrgbaSource[s_auiTopPixelMapping[uiPixel]];
+			ColorFloatRGBA *pfrgbaBottom = &m_pafrgbaSource[s_auiBottomPixelMapping[uiPixel]];
+
+			float fLeftGrayError = CalcGrayDistance2(*pfrgbaLeft, m_frgbaSourceAverageLeft);
+			float fRightGrayError = CalcGrayDistance2(*pfrgbaRight, m_frgbaSourceAverageRight);
+			float fTopGrayError = CalcGrayDistance2(*pfrgbaTop, m_frgbaSourceAverageTop);
+			float fBottomGrayError = CalcGrayDistance2(*pfrgbaBottom, m_frgbaSourceAverageBottom);
+
+			fLeftGrayErrorSum += fLeftGrayError;
+			fRightGrayErrorSum += fRightGrayError;
+			fTopGrayErrorSum += fTopGrayError;
+			fBottomGrayErrorSum += fBottomGrayError;
+		}
+
+		if (DEBUG_PRINT)
+		{
+			printf("\n%.2f %.2f\n", fLeftGrayErrorSum + fRightGrayErrorSum, fTopGrayErrorSum + fBottomGrayErrorSum);
+		}
+
+		m_boolMostLikelyFlip = (fTopGrayErrorSum + fBottomGrayErrorSum) < (fLeftGrayErrorSum + fRightGrayErrorSum);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// calculate source pixel averages for each 2x2 quadrant in a 4x4 block
+	// these are used to determine the averages for each of the 4 different halves (left, right, top, bottom)
+	// ignore pixels that have alpha == NAN (these are border pixels outside of the source image)
+	// weight the averages based on a pixel's alpha
+	//
+	void Block4x4Encoding_ETC1::CalculateSourceAverages(void)
+	{
+		static const bool DEBUG_PRINT = false;
+
+		bool boolRGBX = m_pblockParent->GetImageSource()->GetErrorMetric() == ErrorMetric::RGBX;
+
+		if (m_pblockParent->GetSourceAlphaMix() == Block4x4::SourceAlphaMix::OPAQUE || boolRGBX)
+		{
+			ColorFloatRGBA frgbaSumUL = m_pafrgbaSource[0] + m_pafrgbaSource[1] + m_pafrgbaSource[4] + m_pafrgbaSource[5];
+			ColorFloatRGBA frgbaSumLL = m_pafrgbaSource[2] + m_pafrgbaSource[3] + m_pafrgbaSource[6] + m_pafrgbaSource[7];
+			ColorFloatRGBA frgbaSumUR = m_pafrgbaSource[8] + m_pafrgbaSource[9] + m_pafrgbaSource[12] + m_pafrgbaSource[13];
+			ColorFloatRGBA frgbaSumLR = m_pafrgbaSource[10] + m_pafrgbaSource[11] + m_pafrgbaSource[14] + m_pafrgbaSource[15];
+
+			m_frgbaSourceAverageLeft = (frgbaSumUL + frgbaSumLL) * 0.125f;
+			m_frgbaSourceAverageRight = (frgbaSumUR + frgbaSumLR) * 0.125f;
+			m_frgbaSourceAverageTop = (frgbaSumUL + frgbaSumUR) * 0.125f;
+			m_frgbaSourceAverageBottom = (frgbaSumLL + frgbaSumLR) * 0.125f;
+		}
+		else
+		{
+			float afSourceAlpha[PIXELS];
+
+			// treat alpha NAN as 0.0f
+			for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+			{
+				afSourceAlpha[uiPixel] = isnan(m_pafrgbaSource[uiPixel].fA) ? 
+																		0.0f : 
+																		m_pafrgbaSource[uiPixel].fA;
+			}
+
+			ColorFloatRGBA afrgbaAlphaWeightedSource[PIXELS];
+			for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+			{
+				afrgbaAlphaWeightedSource[uiPixel] = m_pafrgbaSource[uiPixel] * afSourceAlpha[uiPixel];
+			}
+
+			ColorFloatRGBA frgbaSumUL = afrgbaAlphaWeightedSource[0] +
+										afrgbaAlphaWeightedSource[1] +
+										afrgbaAlphaWeightedSource[4] +
+										afrgbaAlphaWeightedSource[5];
+
+			ColorFloatRGBA frgbaSumLL = afrgbaAlphaWeightedSource[2] +
+										afrgbaAlphaWeightedSource[3] +
+										afrgbaAlphaWeightedSource[6] +
+										afrgbaAlphaWeightedSource[7];
+
+			ColorFloatRGBA frgbaSumUR = afrgbaAlphaWeightedSource[8] +
+										afrgbaAlphaWeightedSource[9] +
+										afrgbaAlphaWeightedSource[12] +
+										afrgbaAlphaWeightedSource[13];
+
+			ColorFloatRGBA frgbaSumLR = afrgbaAlphaWeightedSource[10] +
+										afrgbaAlphaWeightedSource[11] +
+										afrgbaAlphaWeightedSource[14] +
+										afrgbaAlphaWeightedSource[15];
+
+			float fWeightSumUL = afSourceAlpha[0] +
+									afSourceAlpha[1] +
+									afSourceAlpha[4] +
+									afSourceAlpha[5];
+
+			float fWeightSumLL = afSourceAlpha[2] +
+									afSourceAlpha[3] +
+									afSourceAlpha[6] +
+									afSourceAlpha[7];
+
+			float fWeightSumUR = afSourceAlpha[8] +
+									afSourceAlpha[9] +
+									afSourceAlpha[12] +
+									afSourceAlpha[13];
+
+			float fWeightSumLR = afSourceAlpha[10] +
+									afSourceAlpha[11] +
+									afSourceAlpha[14] +
+									afSourceAlpha[15];
+
+			ColorFloatRGBA frgbaSumLeft = frgbaSumUL + frgbaSumLL;
+			ColorFloatRGBA frgbaSumRight = frgbaSumUR + frgbaSumLR;
+			ColorFloatRGBA frgbaSumTop = frgbaSumUL + frgbaSumUR;
+			ColorFloatRGBA frgbaSumBottom = frgbaSumLL + frgbaSumLR;
+
+			float fWeightSumLeft = fWeightSumUL + fWeightSumLL;
+			float fWeightSumRight = fWeightSumUR + fWeightSumLR;
+			float fWeightSumTop = fWeightSumUL + fWeightSumUR;
+			float fWeightSumBottom = fWeightSumLL + fWeightSumLR;
+
+			// check to see if there is at least 1 pixel with  non-zero alpha
+			// completely transparent block should not make it to this code
+			assert((fWeightSumLeft + fWeightSumRight) > 0.0f);
+			assert((fWeightSumTop + fWeightSumBottom) > 0.0f);
+
+			if (fWeightSumLeft > 0.0f)
+			{
+				m_frgbaSourceAverageLeft = frgbaSumLeft * (1.0f/fWeightSumLeft);
+			}
+			if (fWeightSumRight > 0.0f)
+			{
+				m_frgbaSourceAverageRight = frgbaSumRight * (1.0f/fWeightSumRight);
+			}
+			if (fWeightSumTop > 0.0f)
+			{
+				m_frgbaSourceAverageTop = frgbaSumTop * (1.0f/fWeightSumTop);
+			}
+			if (fWeightSumBottom > 0.0f)
+			{
+				m_frgbaSourceAverageBottom = frgbaSumBottom * (1.0f/fWeightSumBottom);
+			}
+
+			if (fWeightSumLeft == 0.0f)
+			{
+				assert(fWeightSumRight > 0.0f);
+				m_frgbaSourceAverageLeft = m_frgbaSourceAverageRight;
+			}
+			if (fWeightSumRight == 0.0f)
+			{
+				assert(fWeightSumLeft > 0.0f);
+				m_frgbaSourceAverageRight = m_frgbaSourceAverageLeft;
+			}
+			if (fWeightSumTop == 0.0f)
+			{
+				assert(fWeightSumBottom > 0.0f);
+				m_frgbaSourceAverageTop = m_frgbaSourceAverageBottom;
+			}
+			if (fWeightSumBottom == 0.0f)
+			{
+				assert(fWeightSumTop > 0.0f);
+				m_frgbaSourceAverageBottom = m_frgbaSourceAverageTop;
+			}
+		}
+
+		
+
+		if (DEBUG_PRINT)
+		{
+			printf("\ntarget: [%.2f,%.2f,%.2f] [%.2f,%.2f,%.2f] [%.2f,%.2f,%.2f] [%.2f,%.2f,%.2f]\n",
+				m_frgbaSourceAverageLeft.fR, m_frgbaSourceAverageLeft.fG, m_frgbaSourceAverageLeft.fB,
+				m_frgbaSourceAverageRight.fR, m_frgbaSourceAverageRight.fG, m_frgbaSourceAverageRight.fB,
+				m_frgbaSourceAverageTop.fR, m_frgbaSourceAverageTop.fG, m_frgbaSourceAverageTop.fB,
+				m_frgbaSourceAverageBottom.fR, m_frgbaSourceAverageBottom.fG, m_frgbaSourceAverageBottom.fB);
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try an ETC1 differential mode encoding
+	// use a_boolFlip to set the encoding F bit
+	// use a_uiRadius to alter basecolor components in the range[-a_uiRadius:a_uiRadius]
+	// use a_iGrayOffset1 and a_iGrayOffset2 to offset the basecolor to search for degenerate encodings
+	// replace the encoding if the encoding error is less than previous encoding
+	//
+	void Block4x4Encoding_ETC1::TryDifferential(bool a_boolFlip, unsigned int a_uiRadius,
+												int a_iGrayOffset1, int a_iGrayOffset2)
+	{
+
+		ColorFloatRGBA frgbaColor1;
+		ColorFloatRGBA frgbaColor2;
+
+		const unsigned int *pauiPixelMapping1;
+		const unsigned int *pauiPixelMapping2;
+
+		if (a_boolFlip)
+		{
+			frgbaColor1 = m_frgbaSourceAverageTop;
+			frgbaColor2 = m_frgbaSourceAverageBottom;
+
+			pauiPixelMapping1 = s_auiTopPixelMapping;
+			pauiPixelMapping2 = s_auiBottomPixelMapping;
+		}
+		else
+		{
+			frgbaColor1 = m_frgbaSourceAverageLeft;
+			frgbaColor2 = m_frgbaSourceAverageRight;
+
+			pauiPixelMapping1 = s_auiLeftPixelMapping;
+			pauiPixelMapping2 = s_auiRightPixelMapping;
+		}
+
+		DifferentialTrys trys(frgbaColor1, frgbaColor2, pauiPixelMapping1, pauiPixelMapping2, 
+								a_uiRadius, a_iGrayOffset1, a_iGrayOffset2);
+
+		Block4x4Encoding_ETC1 encodingTry = *this;
+		encodingTry.m_boolFlip = a_boolFlip;
+
+		encodingTry.TryDifferentialHalf(&trys.m_half1);
+		encodingTry.TryDifferentialHalf(&trys.m_half2);
+
+		// find best halves that are within differential range
+		DifferentialTrys::Try *ptryBest1 = nullptr;
+		DifferentialTrys::Try *ptryBest2 = nullptr;
+		encodingTry.m_fError = FLT_MAX;
+
+		// see if the best of each half are in differential range
+		int iDRed = trys.m_half2.m_ptryBest->m_iRed - trys.m_half1.m_ptryBest->m_iRed;
+		int iDGreen = trys.m_half2.m_ptryBest->m_iGreen - trys.m_half1.m_ptryBest->m_iGreen;
+		int iDBlue = trys.m_half2.m_ptryBest->m_iBlue - trys.m_half1.m_ptryBest->m_iBlue;
+		if (iDRed >= -4 && iDRed <= 3 && iDGreen >= -4 && iDGreen <= 3 && iDBlue >= -4 && iDBlue <= 3)
+		{
+			ptryBest1 = trys.m_half1.m_ptryBest;
+			ptryBest2 = trys.m_half2.m_ptryBest;
+			encodingTry.m_fError = trys.m_half1.m_ptryBest->m_fError + trys.m_half2.m_ptryBest->m_fError;
+		}
+		else
+		{
+			// else, find the next best halves that are in differential range
+			for (DifferentialTrys::Try *ptry1 = &trys.m_half1.m_atry[0];
+			ptry1 < &trys.m_half1.m_atry[trys.m_half1.m_uiTrys];
+				ptry1++)
+			{
+				for (DifferentialTrys::Try *ptry2 = &trys.m_half2.m_atry[0];
+				ptry2 < &trys.m_half2.m_atry[trys.m_half2.m_uiTrys];
+					ptry2++)
+				{
+					iDRed = ptry2->m_iRed - ptry1->m_iRed;
+					bool boolValidRedDelta = iDRed <= 3 && iDRed >= -4;
+					iDGreen = ptry2->m_iGreen - ptry1->m_iGreen;
+					bool boolValidGreenDelta = iDGreen <= 3 && iDGreen >= -4;
+					iDBlue = ptry2->m_iBlue - ptry1->m_iBlue;
+					bool boolValidBlueDelta = iDBlue <= 3 && iDBlue >= -4;
+
+					if (boolValidRedDelta && boolValidGreenDelta && boolValidBlueDelta)
+					{
+						float fError = ptry1->m_fError + ptry2->m_fError;
+
+						if (fError < encodingTry.m_fError)
+						{
+							encodingTry.m_fError = fError;
+
+							ptryBest1 = ptry1;
+							ptryBest2 = ptry2;
+						}
+					}
+
+				}
+			}
+			assert(encodingTry.m_fError < FLT_MAX);
+			assert(ptryBest1 != nullptr);
+			assert(ptryBest2 != nullptr);
+		}
+
+		if (encodingTry.m_fError < m_fError)
+		{
+			m_mode = MODE_ETC1;
+			m_boolDiff = true;
+			m_boolFlip = encodingTry.m_boolFlip;
+			m_frgbaColor1 = ColorFloatRGBA::ConvertFromRGB5((unsigned char)ptryBest1->m_iRed, (unsigned char)ptryBest1->m_iGreen, (unsigned char)ptryBest1->m_iBlue);
+			m_frgbaColor2 = ColorFloatRGBA::ConvertFromRGB5((unsigned char)ptryBest2->m_iRed, (unsigned char)ptryBest2->m_iGreen, (unsigned char)ptryBest2->m_iBlue);
+			m_uiCW1 = ptryBest1->m_uiCW;
+			m_uiCW2 = ptryBest2->m_uiCW;
+
+			for (unsigned int uiPixelOrder = 0; uiPixelOrder < PIXELS / 2; uiPixelOrder++)
+			{
+				unsigned int uiPixel1 = pauiPixelMapping1[uiPixelOrder];
+				unsigned int uiPixel2 = pauiPixelMapping2[uiPixelOrder];
+
+				unsigned int uiSelector1 = ptryBest1->m_auiSelectors[uiPixelOrder];
+				unsigned int uiSelector2 = ptryBest2->m_auiSelectors[uiPixelOrder];
+
+				m_auiSelectors[uiPixel1] = uiSelector1;
+				m_auiSelectors[uiPixel2] = ptryBest2->m_auiSelectors[uiPixelOrder];
+
+				float fDeltaRGB1 = s_aafCwTable[m_uiCW1][uiSelector1];
+				float fDeltaRGB2 = s_aafCwTable[m_uiCW2][uiSelector2];
+
+				m_afrgbaDecodedColors[uiPixel1] = (m_frgbaColor1 + fDeltaRGB1).ClampRGB();
+				m_afrgbaDecodedColors[uiPixel2] = (m_frgbaColor2 + fDeltaRGB2).ClampRGB();
+			}
+
+			m_fError1 = ptryBest1->m_fError;
+			m_fError2 = ptryBest2->m_fError;
+			m_boolSeverelyBentDifferentialColors = trys.m_boolSeverelyBentColors;
+			m_fError = m_fError1 + m_fError2;
+
+			// sanity check
+			{
+				int iRed1 = m_frgbaColor1.IntRed(31.0f);
+				int iGreen1 = m_frgbaColor1.IntGreen(31.0f);
+				int iBlue1 = m_frgbaColor1.IntBlue(31.0f);
+
+				int iRed2 = m_frgbaColor2.IntRed(31.0f);
+				int iGreen2 = m_frgbaColor2.IntGreen(31.0f);
+				int iBlue2 = m_frgbaColor2.IntBlue(31.0f);
+
+				iDRed = iRed2 - iRed1;
+				iDGreen = iGreen2 - iGreen1;
+				iDBlue = iBlue2 - iBlue1;
+
+				assert(iDRed >= -4 && iDRed < 4);
+				assert(iDGreen >= -4 && iDGreen < 4);
+				assert(iDBlue >= -4 && iDBlue < 4);
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try an ETC1 differential mode encoding for a half of a 4x4 block
+	// vary the basecolor components using a radius
+	//
+	void Block4x4Encoding_ETC1::TryDifferentialHalf(DifferentialTrys::Half *a_phalf)
+	{
+
+		a_phalf->m_ptryBest = nullptr;
+		float fBestTryError = FLT_MAX;
+
+		a_phalf->m_uiTrys = 0;
+		for (int iRed = a_phalf->m_iRed - (int)a_phalf->m_uiRadius; 
+				iRed <= a_phalf->m_iRed + (int)a_phalf->m_uiRadius;
+				iRed++)
+		{
+			assert(iRed >= 0 && iRed <= 31);
+
+			for (int iGreen = a_phalf->m_iGreen - (int)a_phalf->m_uiRadius;
+					iGreen <= a_phalf->m_iGreen + (int)a_phalf->m_uiRadius;
+					iGreen++)
+			{
+				assert(iGreen >= 0 && iGreen <= 31);
+
+				for (int iBlue = a_phalf->m_iBlue - (int)a_phalf->m_uiRadius;
+						iBlue <= a_phalf->m_iBlue + (int)a_phalf->m_uiRadius;
+						iBlue++)
+				{
+					assert(iBlue >= 0 && iBlue <= 31);
+
+					DifferentialTrys::Try *ptry = &a_phalf->m_atry[a_phalf->m_uiTrys];
+					assert(ptry < &a_phalf->m_atry[DifferentialTrys::Half::MAX_TRYS]);
+
+					ptry->m_iRed = iRed;
+					ptry->m_iGreen = iGreen;
+					ptry->m_iBlue = iBlue;
+					ptry->m_fError = FLT_MAX;
+					ColorFloatRGBA frgbaColor = ColorFloatRGBA::ConvertFromRGB5((unsigned char)iRed, (unsigned char)iGreen, (unsigned char)iBlue);
+
+					// try each CW
+					for (unsigned int uiCW = 0; uiCW < CW_RANGES; uiCW++)
+					{
+						unsigned int auiPixelSelectors[PIXELS / 2];
+						ColorFloatRGBA	afrgbaDecodedPixels[PIXELS / 2];
+						float afPixelErrors[PIXELS / 2] = { FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX, 
+															FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX };
+
+						// pre-compute decoded pixels for each selector
+						ColorFloatRGBA afrgbaSelectors[SELECTORS];
+						assert(SELECTORS == 4);
+						afrgbaSelectors[0] = (frgbaColor + s_aafCwTable[uiCW][0]).ClampRGB();
+						afrgbaSelectors[1] = (frgbaColor + s_aafCwTable[uiCW][1]).ClampRGB();
+						afrgbaSelectors[2] = (frgbaColor + s_aafCwTable[uiCW][2]).ClampRGB();
+						afrgbaSelectors[3] = (frgbaColor + s_aafCwTable[uiCW][3]).ClampRGB();
+
+						for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+						{
+							ColorFloatRGBA *pfrgbaSourcePixel = &m_pafrgbaSource[a_phalf->m_pauiPixelMapping[uiPixel]];
+							ColorFloatRGBA frgbaDecodedPixel;
+
+							for (unsigned int uiSelector = 0; uiSelector < SELECTORS; uiSelector++)
+							{
+								frgbaDecodedPixel = afrgbaSelectors[uiSelector];
+
+								float fPixelError;
+
+								fPixelError = CalcPixelError(frgbaDecodedPixel, m_afDecodedAlphas[a_phalf->m_pauiPixelMapping[uiPixel]],
+																	*pfrgbaSourcePixel);
+
+								if (fPixelError < afPixelErrors[uiPixel])
+								{
+									auiPixelSelectors[uiPixel] = uiSelector;
+									afrgbaDecodedPixels[uiPixel] = frgbaDecodedPixel;
+									afPixelErrors[uiPixel] = fPixelError;
+								}
+
+							}
+						}
+
+						// add up all pixel errors
+						float fCWError = 0.0f;
+						for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+						{	
+							fCWError += afPixelErrors[uiPixel];
+						}
+
+						// if best CW so far
+						if (fCWError < ptry->m_fError)
+						{
+							ptry->m_uiCW = uiCW;
+							for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+							{
+								ptry->m_auiSelectors[uiPixel] = auiPixelSelectors[uiPixel];
+							}
+							ptry->m_fError = fCWError;
+						}
+
+					}
+
+					if (ptry->m_fError < fBestTryError)
+					{
+						a_phalf->m_ptryBest = ptry;
+						fBestTryError = ptry->m_fError;
+					}
+
+					assert(ptry->m_fError < FLT_MAX);
+
+					a_phalf->m_uiTrys++;
+				}
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try an ETC1 individual mode encoding
+	// use a_boolFlip to set the encoding F bit
+	// use a_uiRadius to alter basecolor components in the range[-a_uiRadius:a_uiRadius]
+	// replace the encoding if the encoding error is less than previous encoding
+	//
+	void Block4x4Encoding_ETC1::TryIndividual(bool a_boolFlip, unsigned int a_uiRadius)
+	{
+
+		ColorFloatRGBA frgbaColor1;
+		ColorFloatRGBA frgbaColor2;
+
+		const unsigned int *pauiPixelMapping1;
+		const unsigned int *pauiPixelMapping2;
+
+		if (a_boolFlip)
+		{
+			frgbaColor1 = m_frgbaSourceAverageTop;
+			frgbaColor2 = m_frgbaSourceAverageBottom;
+
+			pauiPixelMapping1 = s_auiTopPixelMapping;
+			pauiPixelMapping2 = s_auiBottomPixelMapping;
+		}
+		else
+		{
+			frgbaColor1 = m_frgbaSourceAverageLeft;
+			frgbaColor2 = m_frgbaSourceAverageRight;
+
+			pauiPixelMapping1 = s_auiLeftPixelMapping;
+			pauiPixelMapping2 = s_auiRightPixelMapping;
+		}
+
+		IndividualTrys trys(frgbaColor1, frgbaColor2, pauiPixelMapping1, pauiPixelMapping2, a_uiRadius);
+
+		Block4x4Encoding_ETC1 encodingTry = *this;
+		encodingTry.m_boolFlip = a_boolFlip;
+
+		encodingTry.TryIndividualHalf(&trys.m_half1);
+		encodingTry.TryIndividualHalf(&trys.m_half2);
+
+		// use the best of each half
+		IndividualTrys::Try *ptryBest1 = trys.m_half1.m_ptryBest;
+		IndividualTrys::Try *ptryBest2 = trys.m_half2.m_ptryBest;
+		encodingTry.m_fError = trys.m_half1.m_ptryBest->m_fError + trys.m_half2.m_ptryBest->m_fError;
+
+		if (encodingTry.m_fError < m_fError)
+		{
+			m_mode = MODE_ETC1;
+			m_boolDiff = false;
+			m_boolFlip = encodingTry.m_boolFlip;
+			m_frgbaColor1 = ColorFloatRGBA::ConvertFromRGB4((unsigned char)ptryBest1->m_iRed, (unsigned char)ptryBest1->m_iGreen, (unsigned char)ptryBest1->m_iBlue);
+			m_frgbaColor2 = ColorFloatRGBA::ConvertFromRGB4((unsigned char)ptryBest2->m_iRed, (unsigned char)ptryBest2->m_iGreen, (unsigned char)ptryBest2->m_iBlue);
+			m_uiCW1 = ptryBest1->m_uiCW;
+			m_uiCW2 = ptryBest2->m_uiCW;
+
+			for (unsigned int uiPixelOrder = 0; uiPixelOrder < PIXELS / 2; uiPixelOrder++)
+			{
+				unsigned int uiPixel1 = pauiPixelMapping1[uiPixelOrder];
+				unsigned int uiPixel2 = pauiPixelMapping2[uiPixelOrder];
+
+				unsigned int uiSelector1 = ptryBest1->m_auiSelectors[uiPixelOrder];
+				unsigned int uiSelector2 = ptryBest2->m_auiSelectors[uiPixelOrder];
+
+				m_auiSelectors[uiPixel1] = uiSelector1;
+				m_auiSelectors[uiPixel2] = ptryBest2->m_auiSelectors[uiPixelOrder];
+
+				float fDeltaRGB1 = s_aafCwTable[m_uiCW1][uiSelector1];
+				float fDeltaRGB2 = s_aafCwTable[m_uiCW2][uiSelector2];
+
+				m_afrgbaDecodedColors[uiPixel1] = (m_frgbaColor1 + fDeltaRGB1).ClampRGB();
+				m_afrgbaDecodedColors[uiPixel2] = (m_frgbaColor2 + fDeltaRGB2).ClampRGB();
+			}
+
+			m_fError1 = ptryBest1->m_fError;
+			m_fError2 = ptryBest2->m_fError;
+			m_fError = m_fError1 + m_fError2;
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try an ETC1 differential mode encoding for a half of a 4x4 block
+	// vary the basecolor components using a radius
+	//
+	void Block4x4Encoding_ETC1::TryIndividualHalf(IndividualTrys::Half *a_phalf)
+	{
+
+		a_phalf->m_ptryBest = nullptr;
+		float fBestTryError = FLT_MAX;
+
+		a_phalf->m_uiTrys = 0;
+		for (int iRed = a_phalf->m_iRed - (int)a_phalf->m_uiRadius;
+			iRed <= a_phalf->m_iRed + (int)a_phalf->m_uiRadius;
+			iRed++)
+		{
+			assert(iRed >= 0 && iRed <= 15);
+
+			for (int iGreen = a_phalf->m_iGreen - (int)a_phalf->m_uiRadius;
+				iGreen <= a_phalf->m_iGreen + (int)a_phalf->m_uiRadius;
+				iGreen++)
+			{
+				assert(iGreen >= 0 && iGreen <= 15);
+
+				for (int iBlue = a_phalf->m_iBlue - (int)a_phalf->m_uiRadius;
+					iBlue <= a_phalf->m_iBlue + (int)a_phalf->m_uiRadius;
+					iBlue++)
+				{
+					assert(iBlue >= 0 && iBlue <= 15);
+
+					IndividualTrys::Try *ptry = &a_phalf->m_atry[a_phalf->m_uiTrys];
+					assert(ptry < &a_phalf->m_atry[IndividualTrys::Half::MAX_TRYS]);
+
+					ptry->m_iRed = iRed;
+					ptry->m_iGreen = iGreen;
+					ptry->m_iBlue = iBlue;
+					ptry->m_fError = FLT_MAX;
+					ColorFloatRGBA frgbaColor = ColorFloatRGBA::ConvertFromRGB4((unsigned char)iRed, (unsigned char)iGreen, (unsigned char)iBlue);
+
+					// try each CW
+					for (unsigned int uiCW = 0; uiCW < CW_RANGES; uiCW++)
+					{
+						unsigned int auiPixelSelectors[PIXELS / 2];
+						ColorFloatRGBA	afrgbaDecodedPixels[PIXELS / 2];
+						float afPixelErrors[PIXELS / 2] = { FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX,
+															FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX };
+
+						// pre-compute decoded pixels for each selector
+						ColorFloatRGBA afrgbaSelectors[SELECTORS];
+						assert(SELECTORS == 4);
+						afrgbaSelectors[0] = (frgbaColor + s_aafCwTable[uiCW][0]).ClampRGB();
+						afrgbaSelectors[1] = (frgbaColor + s_aafCwTable[uiCW][1]).ClampRGB();
+						afrgbaSelectors[2] = (frgbaColor + s_aafCwTable[uiCW][2]).ClampRGB();
+						afrgbaSelectors[3] = (frgbaColor + s_aafCwTable[uiCW][3]).ClampRGB();
+
+						for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+						{
+							ColorFloatRGBA *pfrgbaSourcePixel = &m_pafrgbaSource[a_phalf->m_pauiPixelMapping[uiPixel]];
+							ColorFloatRGBA frgbaDecodedPixel;
+
+							for (unsigned int uiSelector = 0; uiSelector < SELECTORS; uiSelector++)
+							{
+								frgbaDecodedPixel = afrgbaSelectors[uiSelector];
+
+								float fPixelError;
+
+								fPixelError = CalcPixelError(frgbaDecodedPixel, m_afDecodedAlphas[a_phalf->m_pauiPixelMapping[uiPixel]],
+										*pfrgbaSourcePixel);
+
+								if (fPixelError < afPixelErrors[uiPixel])
+								{
+									auiPixelSelectors[uiPixel] = uiSelector;
+									afrgbaDecodedPixels[uiPixel] = frgbaDecodedPixel;
+									afPixelErrors[uiPixel] = fPixelError;
+								}
+
+							}
+						}
+
+						// add up all pixel errors
+						float fCWError = 0.0f;
+						for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+						{
+							fCWError += afPixelErrors[uiPixel];
+						}
+
+						// if best CW so far
+						if (fCWError < ptry->m_fError)
+						{
+							ptry->m_uiCW = uiCW;
+							for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+							{
+								ptry->m_auiSelectors[uiPixel] = auiPixelSelectors[uiPixel];
+							}
+							ptry->m_fError = fCWError;
+						}
+
+					}
+
+					if (ptry->m_fError < fBestTryError)
+					{
+						a_phalf->m_ptryBest = ptry;
+						fBestTryError = ptry->m_fError;
+					}
+
+					assert(ptry->m_fError < FLT_MAX);
+
+					a_phalf->m_uiTrys++;
+				}
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try version 1 of the degenerate search
+	// degenerate encodings use basecolor movement and a subset of the selectors to find useful encodings
+	// each subsequent version of the degenerate search uses more basecolor movement and is less likely to
+	//		be successfull
+	//
+	void Block4x4Encoding_ETC1::TryDegenerates1(void)
+	{
+
+		TryDifferential(m_boolMostLikelyFlip, 1, -2, 0);
+		TryDifferential(m_boolMostLikelyFlip, 1, 2, 0);
+		TryDifferential(m_boolMostLikelyFlip, 1, 0, 2);
+		TryDifferential(m_boolMostLikelyFlip, 1, 0, -2);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try version 2 of the degenerate search
+	// degenerate encodings use basecolor movement and a subset of the selectors to find useful encodings
+	// each subsequent version of the degenerate search uses more basecolor movement and is less likely to
+	//		be successfull
+	//
+	void Block4x4Encoding_ETC1::TryDegenerates2(void)
+	{
+
+		TryDifferential(!m_boolMostLikelyFlip, 1, -2, 0);
+		TryDifferential(!m_boolMostLikelyFlip, 1, 2, 0);
+		TryDifferential(!m_boolMostLikelyFlip, 1, 0, 2);
+		TryDifferential(!m_boolMostLikelyFlip, 1, 0, -2);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try version 3 of the degenerate search
+	// degenerate encodings use basecolor movement and a subset of the selectors to find useful encodings
+	// each subsequent version of the degenerate search uses more basecolor movement and is less likely to
+	//		be successfull
+	//
+	void Block4x4Encoding_ETC1::TryDegenerates3(void)
+	{
+
+		TryDifferential(m_boolMostLikelyFlip, 1, -2, -2);
+		TryDifferential(m_boolMostLikelyFlip, 1, -2, 2);
+		TryDifferential(m_boolMostLikelyFlip, 1, 2, -2);
+		TryDifferential(m_boolMostLikelyFlip, 1, 2, 2);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// try version 4 of the degenerate search
+	// degenerate encodings use basecolor movement and a subset of the selectors to find useful encodings
+	// each subsequent version of the degenerate search uses more basecolor movement and is less likely to
+	//		be successfull
+	//
+	void Block4x4Encoding_ETC1::TryDegenerates4(void)
+	{
+
+		TryDifferential(m_boolMostLikelyFlip, 1, -4, 0);
+		TryDifferential(m_boolMostLikelyFlip, 1, 4, 0);
+		TryDifferential(m_boolMostLikelyFlip, 1, 0, 4);
+		TryDifferential(m_boolMostLikelyFlip, 1, 0, -4);
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// find the best selector for each pixel based on a particular basecolor and CW that have been previously set
+	// calculate the selectors for each half of the block separately
+	// set the block error as the sum of each half's error
+	//
+	void Block4x4Encoding_ETC1::CalculateSelectors()
+	{
+		if (m_boolFlip)
+		{
+			CalculateHalfOfTheSelectors(0, s_auiTopPixelMapping);
+			CalculateHalfOfTheSelectors(1, s_auiBottomPixelMapping);
+		}
+		else
+		{
+			CalculateHalfOfTheSelectors(0, s_auiLeftPixelMapping);
+			CalculateHalfOfTheSelectors(1, s_auiRightPixelMapping);
+		}
+
+		m_fError = m_fError1 + m_fError2;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// choose best selectors for half of the block
+	// calculate the error for half of the block
+	//
+	void Block4x4Encoding_ETC1::CalculateHalfOfTheSelectors(unsigned int a_uiHalf,
+		const unsigned int *pauiPixelMapping)
+	{
+		static const bool DEBUG_PRINT = false;
+
+		ColorFloatRGBA *pfrgbaColor = a_uiHalf ? &m_frgbaColor2 : &m_frgbaColor1;
+		unsigned int *puiCW = a_uiHalf ? &m_uiCW2 : &m_uiCW1;
+
+		float *pfHalfError = a_uiHalf ? &m_fError2 : &m_fError1;
+		*pfHalfError = FLT_MAX;
+
+		// try each CW
+		for (unsigned int uiCW = 0; uiCW < CW_RANGES; uiCW++)
+		{
+			if (DEBUG_PRINT)
+			{
+				printf("\ncw=%u\n", uiCW);
+			}
+
+			unsigned int auiPixelSelectors[PIXELS / 2];
+			ColorFloatRGBA	afrgbaDecodedPixels[PIXELS / 2];
+			float afPixelErrors[PIXELS / 2] = { FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX };
+
+			for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+			{
+				if (DEBUG_PRINT)
+				{
+					printf("\tsource [%.2f,%.2f,%.2f]\n", m_pafrgbaSource[pauiPixelMapping[uiPixel]].fR,
+						m_pafrgbaSource[pauiPixelMapping[uiPixel]].fG, m_pafrgbaSource[pauiPixelMapping[uiPixel]].fB);
+				}
+
+				ColorFloatRGBA *pfrgbaSourcePixel = &m_pafrgbaSource[pauiPixelMapping[uiPixel]];
+				ColorFloatRGBA frgbaDecodedPixel;
+
+				for (unsigned int uiSelector = 0; uiSelector < SELECTORS; uiSelector++)
+				{
+					float fDeltaRGB = s_aafCwTable[uiCW][uiSelector];
+
+					frgbaDecodedPixel = (*pfrgbaColor + fDeltaRGB).ClampRGB();
+
+					float fPixelError;
+					
+					fPixelError = CalcPixelError(frgbaDecodedPixel, m_afDecodedAlphas[pauiPixelMapping[uiPixel]],
+														*pfrgbaSourcePixel);
+					
+					if (DEBUG_PRINT)
+					{
+						printf("\tpixel %u, index %u [%.2f,%.2f,%.2f], error %.2f", uiPixel, uiSelector,
+							frgbaDecodedPixel.fR,
+							frgbaDecodedPixel.fG,
+							frgbaDecodedPixel.fB,
+							fPixelError);
+					}
+
+					if (fPixelError < afPixelErrors[uiPixel])
+					{
+						if (DEBUG_PRINT)
+						{
+							printf(" *");
+						}
+
+						auiPixelSelectors[uiPixel] = uiSelector;
+						afrgbaDecodedPixels[uiPixel] = frgbaDecodedPixel;
+						afPixelErrors[uiPixel] = fPixelError;
+					}
+
+					if (DEBUG_PRINT)
+					{
+						printf("\n");
+					}
+				}
+			}
+
+			// add up all pixel errors
+			float fCWError = 0.0f;
+			for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+			{
+				fCWError += afPixelErrors[uiPixel];
+			}
+			if (DEBUG_PRINT)
+			{
+				printf("\terror %.2f\n", fCWError);
+			}
+
+			// if best CW so far
+			if (fCWError < *pfHalfError)
+			{
+				*pfHalfError = fCWError;
+				*puiCW = uiCW;
+				for (unsigned int uiPixel = 0; uiPixel < 8; uiPixel++)
+				{
+					m_auiSelectors[pauiPixelMapping[uiPixel]] = auiPixelSelectors[uiPixel];
+					m_afrgbaDecodedColors[pauiPixelMapping[uiPixel]] = afrgbaDecodedPixels[uiPixel];
+				}
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// set the encoding bits based on encoding state
+	//
+	void Block4x4Encoding_ETC1::SetEncodingBits(void)
+	{
+		assert(m_mode == MODE_ETC1);
+
+		if (m_boolDiff)
+		{
+			int iRed1 = m_frgbaColor1.IntRed(31.0f);
+			int iGreen1 = m_frgbaColor1.IntGreen(31.0f);
+			int iBlue1 = m_frgbaColor1.IntBlue(31.0f);
+
+			int iRed2 = m_frgbaColor2.IntRed(31.0f);
+			int iGreen2 = m_frgbaColor2.IntGreen(31.0f);
+			int iBlue2 = m_frgbaColor2.IntBlue(31.0f);
+
+			int iDRed2 = iRed2 - iRed1;
+			int iDGreen2 = iGreen2 - iGreen1;
+			int iDBlue2 = iBlue2 - iBlue1;
+
+			assert(iDRed2 >= -4 && iDRed2 < 4);
+			assert(iDGreen2 >= -4 && iDGreen2 < 4);
+			assert(iDBlue2 >= -4 && iDBlue2 < 4);
+
+			m_pencodingbitsRGB8->differential.red1 = (unsigned int)iRed1;
+			m_pencodingbitsRGB8->differential.green1 = (unsigned int)iGreen1;
+			m_pencodingbitsRGB8->differential.blue1 = (unsigned int)iBlue1;
+
+			m_pencodingbitsRGB8->differential.dred2 = iDRed2;
+			m_pencodingbitsRGB8->differential.dgreen2 = iDGreen2;
+			m_pencodingbitsRGB8->differential.dblue2 = iDBlue2;
+		}
+		else
+		{
+			m_pencodingbitsRGB8->individual.red1 = (unsigned int)m_frgbaColor1.IntRed(15.0f);
+			m_pencodingbitsRGB8->individual.green1 = (unsigned int)m_frgbaColor1.IntGreen(15.0f);
+			m_pencodingbitsRGB8->individual.blue1 = (unsigned int)m_frgbaColor1.IntBlue(15.0f);
+
+			m_pencodingbitsRGB8->individual.red2 = (unsigned int)m_frgbaColor2.IntRed(15.0f);
+			m_pencodingbitsRGB8->individual.green2 = (unsigned int)m_frgbaColor2.IntGreen(15.0f);
+			m_pencodingbitsRGB8->individual.blue2 = (unsigned int)m_frgbaColor2.IntBlue(15.0f);
+		}
+
+		m_pencodingbitsRGB8->individual.cw1 = m_uiCW1;
+		m_pencodingbitsRGB8->individual.cw2 = m_uiCW2;
+
+		SetEncodingBits_Selectors();
+
+		m_pencodingbitsRGB8->individual.diff = (unsigned int)m_boolDiff;
+		m_pencodingbitsRGB8->individual.flip = (unsigned int)m_boolFlip;
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// set the selectors in the encoding bits
+	//
+	void Block4x4Encoding_ETC1::SetEncodingBits_Selectors(void)
+	{
+
+		m_pencodingbitsRGB8->individual.selectors = 0;
+		for (unsigned int uiPixel = 0; uiPixel < PIXELS; uiPixel++)
+		{
+			unsigned int uiSelector = m_auiSelectors[uiPixel];
+
+			// set index msb
+			m_pencodingbitsRGB8->individual.selectors |= (uiSelector >> 1) << (uiPixel ^ 8);
+
+			// set index lsb
+			m_pencodingbitsRGB8->individual.selectors |= (uiSelector & 1) << ((16 + uiPixel) ^ 8);
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// set the decoded colors and decoded alpha based on the encoding state
+	//
+	void Block4x4Encoding_ETC1::Decode(void)
+	{
+
+		const unsigned int *pauiPixelOrder = m_boolFlip ? s_auiPixelOrderFlip1 : s_auiPixelOrderFlip0;
+
+		for (unsigned int uiPixelOrder = 0; uiPixelOrder < PIXELS; uiPixelOrder++)
+		{
+			ColorFloatRGBA *pfrgbaCenter = uiPixelOrder < 8 ? &m_frgbaColor1 : &m_frgbaColor2;
+			unsigned int uiCW = uiPixelOrder < 8 ? m_uiCW1 : m_uiCW2;
+
+			unsigned int uiPixel = pauiPixelOrder[uiPixelOrder];
+
+			float fDelta = s_aafCwTable[uiCW][m_auiSelectors[uiPixel]];
+			m_afrgbaDecodedColors[uiPixel] = (*pfrgbaCenter + fDelta).ClampRGB();
+			m_afDecodedAlphas[uiPixel] = 1.0f;
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	//
+
+} // namespace Etc