Merge pull request #8548 from tagcup/etc2comp

Add ETC1/ETC2 compression support though etc2comp.

1 files changed, 685 insertions, 0 deletions

diff --git a/thirdparty/etc2comp/EtcImage.cpp b/thirdparty/etc2comp/EtcImage.cpp
new file mode 100644
index 0000000000..7a1058844d
--- /dev/null
+++ b/thirdparty/etc2comp/EtcImage.cpp
@@ -0,0 +1,685 @@
+/*
+ * 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.
+ */
+
+/*
+EtcImage.cpp
+
+Image is an array of 4x4 blocks that represent the encoding of the source image
+
+*/
+
+#include "EtcConfig.h"
+
+#include <stdlib.h>
+
+#include "EtcImage.h"
+
+#include "Etc.h"
+#include "EtcBlock4x4.h"
+#include "EtcBlock4x4EncodingBits.h"
+#include "EtcSortedBlockList.h"
+
+#if ETC_WINDOWS
+#include <windows.h>
+#endif
+#include <ctime>
+#include <chrono>
+#include <future>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+// fix conflict with Block4x4::AlphaMix
+#ifdef OPAQUE
+#undef OPAQUE
+#endif
+#ifdef TRANSPARENT
+#undef TRANSPARENT
+#endif
+
+namespace Etc
+{
+
+	// ----------------------------------------------------------------------------------------------------
+	//
+	Image::Image(void)
+	{
+		m_encodingStatus = EncodingStatus::SUCCESS;
+		m_warningsToCapture = EncodingStatus::SUCCESS;
+		m_pafrgbaSource = nullptr;
+
+		m_pablock = nullptr;
+
+		m_encodingbitsformat = Block4x4EncodingBits::Format::UNKNOWN;
+		m_uiEncodingBitsBytes = 0;
+		m_paucEncodingBits = nullptr;
+
+		m_format = Format::UNKNOWN;
+		m_iNumOpaquePixels = 0;
+		m_iNumTranslucentPixels = 0;
+		m_iNumTransparentPixels = 0;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// constructor using source image
+	// used to set state before Encode() is called
+	//
+	Image::Image(float *a_pafSourceRGBA, unsigned int a_uiSourceWidth,
+					unsigned int a_uiSourceHeight, 
+					ErrorMetric a_errormetric)
+	{
+		m_encodingStatus = EncodingStatus::SUCCESS;
+		m_warningsToCapture = EncodingStatus::SUCCESS;
+		m_pafrgbaSource = (ColorFloatRGBA *) a_pafSourceRGBA;
+		m_uiSourceWidth = a_uiSourceWidth;
+		m_uiSourceHeight = a_uiSourceHeight;
+
+		m_uiExtendedWidth = CalcExtendedDimension((unsigned short)m_uiSourceWidth);
+		m_uiExtendedHeight = CalcExtendedDimension((unsigned short)m_uiSourceHeight);
+
+		m_uiBlockColumns = m_uiExtendedWidth >> 2;
+		m_uiBlockRows = m_uiExtendedHeight >> 2;
+
+		m_pablock = new Block4x4[GetNumberOfBlocks()];
+		assert(m_pablock);
+
+		m_format = Format::UNKNOWN;
+
+		m_encodingbitsformat = Block4x4EncodingBits::Format::UNKNOWN;
+		m_uiEncodingBitsBytes = 0;
+		m_paucEncodingBits = nullptr;
+
+		m_errormetric = a_errormetric;
+		m_fEffort = 0.0f;
+
+		m_iEncodeTime_ms = -1;
+
+		m_iNumOpaquePixels = 0;
+		m_iNumTranslucentPixels = 0;
+		m_iNumTransparentPixels = 0;
+		m_bVerboseOutput = false;
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// constructor using encoding bits
+	// recreates encoding state using a previously encoded image
+	//
+	Image::Image(Format a_format,
+					unsigned int a_uiSourceWidth, unsigned int a_uiSourceHeight,
+					unsigned char *a_paucEncidingBits, unsigned int a_uiEncodingBitsBytes,
+					Image *a_pimageSource, ErrorMetric a_errormetric)
+	{
+		m_encodingStatus = EncodingStatus::SUCCESS;
+		m_pafrgbaSource = nullptr;
+		m_uiSourceWidth = a_uiSourceWidth;
+		m_uiSourceHeight = a_uiSourceHeight;
+
+		m_uiExtendedWidth = CalcExtendedDimension((unsigned short)m_uiSourceWidth);
+		m_uiExtendedHeight = CalcExtendedDimension((unsigned short)m_uiSourceHeight);
+
+		m_uiBlockColumns = m_uiExtendedWidth >> 2;
+		m_uiBlockRows = m_uiExtendedHeight >> 2;
+
+		unsigned int uiBlocks = GetNumberOfBlocks();
+
+		m_pablock = new Block4x4[uiBlocks];
+		assert(m_pablock);
+
+		m_format = a_format;
+
+		m_iNumOpaquePixels = 0;
+		m_iNumTranslucentPixels = 0;
+		m_iNumTransparentPixels = 0;
+		
+		m_encodingbitsformat = DetermineEncodingBitsFormat(m_format);
+		if (m_encodingbitsformat == Block4x4EncodingBits::Format::UNKNOWN)
+		{
+			AddToEncodingStatus(ERROR_UNKNOWN_FORMAT);
+			return;
+		}
+		m_uiEncodingBitsBytes = a_uiEncodingBitsBytes;
+		m_paucEncodingBits = a_paucEncidingBits;
+
+		m_errormetric = a_errormetric;
+		m_fEffort = 0.0f;
+		m_bVerboseOutput = false;
+		m_iEncodeTime_ms = -1;
+		
+		unsigned char *paucEncodingBits = m_paucEncodingBits;
+		unsigned int uiEncodingBitsBytesPerBlock = Block4x4EncodingBits::GetBytesPerBlock(m_encodingbitsformat);
+
+		unsigned int uiH = 0;
+		unsigned int uiV = 0;
+		for (unsigned int uiBlock = 0; uiBlock < uiBlocks; uiBlock++)
+		{
+			m_pablock[uiBlock].InitFromEtcEncodingBits(a_format, uiH, uiV, paucEncodingBits, 
+														a_pimageSource, a_errormetric);
+			paucEncodingBits += uiEncodingBitsBytesPerBlock;
+			uiH += 4;
+			if (uiH >= m_uiSourceWidth)
+			{
+				uiH = 0;
+				uiV += 4;
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	//
+	Image::~Image(void)
+	{
+		if (m_pablock != nullptr)
+		{
+			delete[] m_pablock;
+			m_pablock = nullptr;
+		}
+
+		/*if (m_paucEncodingBits != nullptr)
+		{
+			delete[] m_paucEncodingBits;
+			m_paucEncodingBits = nullptr;
+		}*/
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// encode an image
+	// create a set of encoding bits that conforms to a_format
+	// find best fit using a_errormetric
+	// explore a range of possible encodings based on a_fEffort (range = [0:100])
+	// speed up process using a_uiJobs as the number of process threads (a_uiJobs must not excede a_uiMaxJobs)
+	//
+	Image::EncodingStatus Image::Encode(Format a_format, ErrorMetric a_errormetric, float a_fEffort, unsigned int a_uiJobs, unsigned int a_uiMaxJobs)
+	{
+
+		auto start = std::chrono::steady_clock::now();
+		
+		m_encodingStatus = EncodingStatus::SUCCESS;
+
+		m_format = a_format;
+		m_errormetric = a_errormetric;
+		m_fEffort = a_fEffort;
+
+		if (m_errormetric < 0 || m_errormetric > ERROR_METRICS)
+		{
+			AddToEncodingStatus(ERROR_UNKNOWN_ERROR_METRIC);
+			return m_encodingStatus;
+		}
+
+		if (m_fEffort < ETCCOMP_MIN_EFFORT_LEVEL)
+		{
+			AddToEncodingStatus(WARNING_EFFORT_OUT_OF_RANGE);
+			m_fEffort = ETCCOMP_MIN_EFFORT_LEVEL;
+		}
+		else if (m_fEffort > ETCCOMP_MAX_EFFORT_LEVEL)
+		{
+			AddToEncodingStatus(WARNING_EFFORT_OUT_OF_RANGE);
+			m_fEffort = ETCCOMP_MAX_EFFORT_LEVEL;
+		}
+		if (a_uiJobs < 1)
+		{
+			a_uiJobs = 1;
+			AddToEncodingStatus(WARNING_JOBS_OUT_OF_RANGE);
+		}
+		else if (a_uiJobs > a_uiMaxJobs)
+		{
+			a_uiJobs = a_uiMaxJobs;
+			AddToEncodingStatus(WARNING_JOBS_OUT_OF_RANGE);
+		}
+
+		m_encodingbitsformat = DetermineEncodingBitsFormat(m_format);
+
+		if (m_encodingbitsformat == Block4x4EncodingBits::Format::UNKNOWN)
+		{
+			AddToEncodingStatus(ERROR_UNKNOWN_FORMAT);
+			return m_encodingStatus;
+		}
+
+		assert(m_paucEncodingBits == nullptr);
+		m_uiEncodingBitsBytes = GetNumberOfBlocks() * Block4x4EncodingBits::GetBytesPerBlock(m_encodingbitsformat);
+		m_paucEncodingBits = new unsigned char[m_uiEncodingBitsBytes];
+
+		InitBlocksAndBlockSorter();
+
+
+		std::future<void> *handle = new std::future<void>[a_uiMaxJobs];
+
+		unsigned int uiNumThreadsNeeded = 0;
+		unsigned int uiUnfinishedBlocks = GetNumberOfBlocks();
+
+		uiNumThreadsNeeded = (uiUnfinishedBlocks < a_uiJobs) ? uiUnfinishedBlocks : a_uiJobs;
+			
+		for (int i = 0; i < (int)uiNumThreadsNeeded - 1; i++)
+		{
+			handle[i] = async(std::launch::async, &Image::RunFirstPass, this, i, uiNumThreadsNeeded);
+		}
+
+		RunFirstPass(uiNumThreadsNeeded - 1, uiNumThreadsNeeded);
+
+		for (int i = 0; i < (int)uiNumThreadsNeeded - 1; i++)
+		{
+			handle[i].get();
+		}
+
+		// perform effort-based encoding
+		if (m_fEffort > ETCCOMP_MIN_EFFORT_LEVEL)
+		{
+			unsigned int uiFinishedBlocks = 0;
+			unsigned int uiTotalEffortBlocks = static_cast<unsigned int>(roundf(0.01f * m_fEffort  * GetNumberOfBlocks()));
+
+			if (m_bVerboseOutput)
+			{
+				printf("effortblocks = %d\n", uiTotalEffortBlocks);
+			}
+			unsigned int uiPass = 0;
+			while (1)
+			{
+				if (m_bVerboseOutput)
+				{
+					uiPass++;
+					printf("pass %u\n", uiPass);
+				}
+				m_psortedblocklist->Sort();
+				uiUnfinishedBlocks = m_psortedblocklist->GetNumberOfSortedBlocks();
+				uiFinishedBlocks = GetNumberOfBlocks() - uiUnfinishedBlocks;
+				if (m_bVerboseOutput)
+				{
+					printf("    %u unfinished blocks\n", uiUnfinishedBlocks);
+					// m_psortedblocklist->Print();
+				}
+
+				
+
+				//stop enocding when we did enough to satify the effort percentage
+				if (uiFinishedBlocks >= uiTotalEffortBlocks)
+				{
+					if (m_bVerboseOutput)
+					{
+						printf("Finished %d Blocks out of %d\n", uiFinishedBlocks, uiTotalEffortBlocks);
+					}
+					break;
+				}
+
+				unsigned int uiIteratedBlocks = 0;
+				unsigned int blocksToIterateThisPass = (uiTotalEffortBlocks - uiFinishedBlocks);
+				uiNumThreadsNeeded = (uiUnfinishedBlocks < a_uiJobs) ? uiUnfinishedBlocks : a_uiJobs;
+
+				if (uiNumThreadsNeeded <= 1)
+				{
+					//since we already how many blocks each thread will process
+					//cap the thread limit to do the proper amount of work, and not more
+					uiIteratedBlocks = IterateThroughWorstBlocks(blocksToIterateThisPass, 0, 1);
+				}
+				else
+				{
+					//we have a lot of work to do, so lets multi thread it
+					std::future<unsigned int> *handleToBlockEncoders = new std::future<unsigned int>[uiNumThreadsNeeded-1];
+
+					for (int i = 0; i < (int)uiNumThreadsNeeded - 1; i++)
+					{
+						handleToBlockEncoders[i] = async(std::launch::async, &Image::IterateThroughWorstBlocks, this, blocksToIterateThisPass, i, uiNumThreadsNeeded);
+					}
+					uiIteratedBlocks = IterateThroughWorstBlocks(blocksToIterateThisPass, uiNumThreadsNeeded - 1, uiNumThreadsNeeded);
+
+					for (int i = 0; i < (int)uiNumThreadsNeeded - 1; i++)
+					{
+						uiIteratedBlocks += handleToBlockEncoders[i].get();
+					}
+
+					delete[] handleToBlockEncoders;
+				}
+
+				if (m_bVerboseOutput)
+				{
+					printf("    %u iterated blocks\n", uiIteratedBlocks);
+				}
+			}
+		}
+
+		// generate Etc2-compatible bit-format 4x4 blocks
+		for (int i = 0; i < (int)a_uiJobs - 1; i++)
+		{
+			handle[i] = async(std::launch::async, &Image::SetEncodingBits, this, i, a_uiJobs);
+		}
+		SetEncodingBits(a_uiJobs - 1, a_uiJobs);
+
+		for (int i = 0; i < (int)a_uiJobs - 1; i++)
+		{
+			handle[i].get();
+		}
+
+		auto end = std::chrono::steady_clock::now();
+		std::chrono::milliseconds elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
+		m_iEncodeTime_ms = (int)elapsed.count();
+
+		delete[] handle;
+		delete m_psortedblocklist;
+		return m_encodingStatus;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// iterate the encoding thru the blocks with the worst error
+	// stop when a_uiMaxBlocks blocks have been iterated
+	// split the blocks between the process threads using a_uiMultithreadingOffset and a_uiMultithreadingStride
+	//
+	unsigned int Image::IterateThroughWorstBlocks(unsigned int a_uiMaxBlocks, 
+													unsigned int a_uiMultithreadingOffset, 
+													unsigned int a_uiMultithreadingStride)
+	{
+		assert(a_uiMultithreadingStride > 0);
+		unsigned int uiIteratedBlocks = a_uiMultithreadingOffset;
+
+		SortedBlockList::Link *plink = m_psortedblocklist->GetLinkToFirstBlock();
+		for (plink = plink->Advance(a_uiMultithreadingOffset);
+				plink != nullptr;
+				plink = plink->Advance(a_uiMultithreadingStride) )
+		{
+			if (uiIteratedBlocks >= a_uiMaxBlocks)
+			{
+				break;
+			}
+
+			plink->GetBlock()->PerformEncodingIteration(m_fEffort);
+
+			uiIteratedBlocks += a_uiMultithreadingStride;	
+		}
+
+		return uiIteratedBlocks;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// determine which warnings to check for during Encode() based on encoding format
+	//
+	void Image::FindEncodingWarningTypesForCurFormat()
+	{
+		TrackEncodingWarning(WARNING_ALL_TRANSPARENT_PIXELS);
+		TrackEncodingWarning(WARNING_SOME_RGBA_NOT_0_TO_1);
+		switch (m_format)
+		{
+		case Image::Format::ETC1:
+		case Image::Format::RGB8:
+		case Image::Format::SRGB8:
+			TrackEncodingWarning(WARNING_SOME_NON_OPAQUE_PIXELS);
+			TrackEncodingWarning(WARNING_SOME_TRANSLUCENT_PIXELS);
+			break;
+
+		case Image::Format::RGB8A1:
+		case Image::Format::SRGB8A1:
+			TrackEncodingWarning(WARNING_SOME_TRANSLUCENT_PIXELS);
+			TrackEncodingWarning(WARNING_ALL_OPAQUE_PIXELS);
+			break;
+		case Image::Format::RGBA8:
+		case Image::Format::SRGBA8:
+			TrackEncodingWarning(WARNING_ALL_OPAQUE_PIXELS);
+			break;
+
+		case Image::Format::R11:
+		case Image::Format::SIGNED_R11:
+			TrackEncodingWarning(WARNING_SOME_NON_OPAQUE_PIXELS);
+			TrackEncodingWarning(WARNING_SOME_TRANSLUCENT_PIXELS);
+			TrackEncodingWarning(WARNING_SOME_GREEN_VALUES_ARE_NOT_ZERO);
+			TrackEncodingWarning(WARNING_SOME_BLUE_VALUES_ARE_NOT_ZERO);
+			break;
+
+		case Image::Format::RG11:
+		case Image::Format::SIGNED_RG11:
+			TrackEncodingWarning(WARNING_SOME_NON_OPAQUE_PIXELS);
+			TrackEncodingWarning(WARNING_SOME_TRANSLUCENT_PIXELS);
+			TrackEncodingWarning(WARNING_SOME_BLUE_VALUES_ARE_NOT_ZERO);
+			break;
+		case Image::Format::FORMATS:
+		case Image::Format::UNKNOWN:
+		default:
+			assert(0);
+			break;
+		}
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// examine source pixels to check for warnings
+	//
+	void Image::FindAndSetEncodingWarnings()
+	{
+		int numPixels = (m_uiBlockRows * 4) * (m_uiBlockColumns * 4);
+		if (m_iNumOpaquePixels == numPixels)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_ALL_OPAQUE_PIXELS);
+		}
+		if (m_iNumOpaquePixels < numPixels)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_NON_OPAQUE_PIXELS);
+		}
+		if (m_iNumTranslucentPixels > 0)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_TRANSLUCENT_PIXELS);
+		}
+		if (m_iNumTransparentPixels == numPixels)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_ALL_TRANSPARENT_PIXELS);
+		}
+		if (m_numColorValues.fB > 0.0f)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_BLUE_VALUES_ARE_NOT_ZERO);
+		}
+		if (m_numColorValues.fG > 0.0f) 
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_GREEN_VALUES_ARE_NOT_ZERO);
+		}
+
+		if (m_numOutOfRangeValues.fR > 0.0f || m_numOutOfRangeValues.fG > 0.0f)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_RGBA_NOT_0_TO_1);
+		}
+		if (m_numOutOfRangeValues.fB > 0.0f || m_numOutOfRangeValues.fA > 0.0f)
+		{
+			AddToEncodingStatusIfSignfigant(Image::EncodingStatus::WARNING_SOME_RGBA_NOT_0_TO_1);
+		}
+	}
+	
+	// ----------------------------------------------------------------------------------------------------
+	// return a string name for a given image format
+	//
+	const char * Image::EncodingFormatToString(Image::Format a_format)
+	{
+		switch (a_format)
+		{
+		case Image::Format::ETC1:
+			return "ETC1";
+		case Image::Format::RGB8:
+			return "RGB8";
+		case Image::Format::SRGB8:
+			return "SRGB8";
+
+		case Image::Format::RGB8A1:
+			return "RGB8A1";
+		case Image::Format::SRGB8A1:
+			return "SRGB8A1";
+		case Image::Format::RGBA8:
+			return "RGBA8";
+		case Image::Format::SRGBA8:
+			return "SRGBA8";
+
+		case Image::Format::R11:
+			return "R11";
+		case Image::Format::SIGNED_R11:
+			return "SIGNED_R11";
+
+		case Image::Format::RG11:
+			return "RG11";
+		case Image::Format::SIGNED_RG11:
+			return "SIGNED_RG11";
+		case Image::Format::FORMATS:
+		case Image::Format::UNKNOWN:
+		default:
+			return "UNKNOWN";
+		}
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// return a string name for the image's format
+	//
+	const char * Image::EncodingFormatToString(void)
+	{
+		return EncodingFormatToString(m_format);
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// init image blocks prior to encoding
+	// init block sorter for subsequent sortings
+	// check for encoding warnings
+	//
+	void Image::InitBlocksAndBlockSorter(void)
+	{
+		
+		FindEncodingWarningTypesForCurFormat();
+
+		// init each block
+		Block4x4 *pblock = m_pablock;
+		unsigned char *paucEncodingBits = m_paucEncodingBits;
+		for (unsigned int uiBlockRow = 0; uiBlockRow < m_uiBlockRows; uiBlockRow++)
+		{
+			unsigned int uiBlockV = uiBlockRow * 4;
+
+			for (unsigned int uiBlockColumn = 0; uiBlockColumn < m_uiBlockColumns; uiBlockColumn++)
+			{
+				unsigned int uiBlockH = uiBlockColumn * 4;
+
+				pblock->InitFromSource(this, uiBlockH, uiBlockV, paucEncodingBits, m_errormetric);
+
+				paucEncodingBits += Block4x4EncodingBits::GetBytesPerBlock(m_encodingbitsformat);
+
+				pblock++;
+			}
+		}
+
+		FindAndSetEncodingWarnings();
+
+		// init block sorter
+		{
+			m_psortedblocklist = new SortedBlockList(GetNumberOfBlocks(), 100);
+
+			for (unsigned int uiBlock = 0; uiBlock < GetNumberOfBlocks(); uiBlock++)
+			{
+				pblock = &m_pablock[uiBlock];
+				m_psortedblocklist->AddBlock(pblock);
+			}
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// run the first pass of the encoder
+	// the encoder generally finds a reasonable, fast encoding
+	// this is run on all blocks regardless of effort to ensure that all blocks have a valid encoding
+	//
+	void Image::RunFirstPass(unsigned int a_uiMultithreadingOffset, unsigned int a_uiMultithreadingStride)
+	{
+		assert(a_uiMultithreadingStride > 0);
+
+		for (unsigned int uiBlock = a_uiMultithreadingOffset;
+				uiBlock < GetNumberOfBlocks(); 
+				uiBlock += a_uiMultithreadingStride)
+		{
+			Block4x4 *pblock = &m_pablock[uiBlock];
+			pblock->PerformEncodingIteration(m_fEffort);
+		}
+	}
+
+    // ----------------------------------------------------------------------------------------------------
+	// set the encoding bits (for the output file) based on the best encoding for each block
+	//
+	void Image::SetEncodingBits(unsigned int a_uiMultithreadingOffset,
+								unsigned int a_uiMultithreadingStride)
+	{
+		assert(a_uiMultithreadingStride > 0);
+
+		for (unsigned int uiBlock = a_uiMultithreadingOffset; 
+				uiBlock < GetNumberOfBlocks(); 
+				uiBlock += a_uiMultithreadingStride)
+		{
+			Block4x4 *pblock = &m_pablock[uiBlock];
+			pblock->SetEncodingBitsFromEncoding();
+		}
+
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// return the image error
+	// image error is the sum of all block errors
+	//
+	float Image::GetError(void)
+	{
+		float fError = 0.0f;
+
+		for (unsigned int uiBlock = 0; uiBlock < GetNumberOfBlocks(); uiBlock++)
+		{
+			Block4x4 *pblock = &m_pablock[uiBlock];
+			fError += pblock->GetError();
+		}
+
+		return fError;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	// determine the encoding bits format based on the encoding format
+	// the encoding bits format is a family of bit encodings that are shared across various encoding formats
+	//
+	Block4x4EncodingBits::Format Image::DetermineEncodingBitsFormat(Format a_format)
+	{
+		Block4x4EncodingBits::Format encodingbitsformat;
+
+		// determine encoding bits format from image format
+		switch (a_format)
+		{
+		case Format::ETC1:
+		case Format::RGB8:
+		case Format::SRGB8:
+			encodingbitsformat = Block4x4EncodingBits::Format::RGB8;
+			break;
+
+		case Format::RGBA8:
+		case Format::SRGBA8:
+			encodingbitsformat = Block4x4EncodingBits::Format::RGBA8;
+			break;
+
+		case Format::R11:
+		case Format::SIGNED_R11:
+			encodingbitsformat = Block4x4EncodingBits::Format::R11;
+			break;
+
+		case Format::RG11:
+		case Format::SIGNED_RG11:
+			encodingbitsformat = Block4x4EncodingBits::Format::RG11;
+			break;
+
+		case Format::RGB8A1:
+		case Format::SRGB8A1:
+			encodingbitsformat = Block4x4EncodingBits::Format::RGB8A1;
+			break;
+
+		default:
+			encodingbitsformat = Block4x4EncodingBits::Format::UNKNOWN;
+			break;
+		}
+
+		return encodingbitsformat;
+	}
+
+	// ----------------------------------------------------------------------------------------------------
+	//
+
+}	// namespace Etc