/** 
 * @file llimagetga.cpp
 *
 * $LicenseInfo:firstyear=2001&license=viewergpl$
 * 
 * Copyright (c) 2001-2007, Linden Research, Inc.
 * 
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlife.com/developers/opensource/gplv2
 * 
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at http://secondlife.com/developers/opensource/flossexception
 * 
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 * 
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
 * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
 * COMPLETENESS OR PERFORMANCE.
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "llimagetga.h"
#include "llerror.h"
#include "llmath.h"

// For expanding 5-bit pixel values to 8-bit with best rounding
// static
const U8 LLImageTGA::s5to8bits[32] = 
	{
		0,   8,  16,  25,  33,  41,  49,  58,
	   66,  74,  82,  90,  99, 107, 115, 123,
	  132, 140, 148, 156, 165, 173, 181, 189,
	  197, 206, 214, 222, 230, 239, 247, 255
	};

inline void LLImageTGA::decodeTruecolorPixel15( U8* dst, const U8* src )
{
    // We expand 5 bit data to 8 bit sample width.
    // The format of the 16-bit (LSB first) input word is
    // xRRRRRGGGGGBBBBB
	U32 t = U32(src[0]) + (U32(src[1]) << 8);
    dst[2] = s5to8bits[t & 0x1F];  // blue
    t >>= 5;
    dst[1] = s5to8bits[t & 0x1F];  // green
    t >>= 5;
    dst[0] = s5to8bits[t & 0x1F];  // red
}

LLImageTGA::LLImageTGA() 
	: LLImageFormatted(IMG_CODEC_TGA),
	  mColorMap( NULL ),
	  mColorMapStart( 0 ),
	  mColorMapLength( 0 ),
	  mColorMapBytesPerEntry( 0 ),
	  mIs15Bit( FALSE )
{
}

LLImageTGA::LLImageTGA(const LLString& file_name) 
	: LLImageFormatted(IMG_CODEC_TGA),
	  mColorMap( NULL ),
	  mColorMapStart( 0 ),
	  mColorMapLength( 0 ),
	  mColorMapBytesPerEntry( 0 ),
	  mIs15Bit( FALSE )
{
	loadFile(file_name);
}

LLImageTGA::~LLImageTGA()
{
	delete mColorMap;
}

BOOL LLImageTGA::updateData()
{
	resetLastError();

	// Check to make sure that this instance has been initialized with data
	if (!getData() || (0 == getDataSize()))
	{
		setLastError("LLImageTGA uninitialized");
		return FALSE;
	}
	
	// Pull image information from the header...
	U8	flags;
	U8	junk[256];

	/****************************************************************************
	**
	**	For more information about the original Truevision TGA(tm) file format,
	**	or for additional information about the new extensions to the
	**	Truevision TGA file, refer to the "Truevision TGA File Format
	**	Specification Version 2.0" available from Truevision or your
	**	Truevision dealer.
	**
	**  FILE STRUCTURE FOR THE ORIGINAL TRUEVISION TGA FILE				
	**	  FIELD 1 :	NUMBER OF CHARACTERS IN ID FIELD (1 BYTES)	
	**	  FIELD 2 :	COLOR MAP TYPE (1 BYTES)			
	**	  FIELD 3 :	IMAGE TYPE CODE (1 BYTES)			
	**					= 0	NO IMAGE DATA INCLUDED		
	**					= 1	UNCOMPRESSED, COLOR-MAPPED IMAGE
	**					= 2	UNCOMPRESSED, TRUE-COLOR IMAGE	
	**					= 3	UNCOMPRESSED, BLACK AND WHITE IMAGE
	**					= 9	RUN-LENGTH ENCODED COLOR-MAPPED IMAGE
	**					= 10 RUN-LENGTH ENCODED TRUE-COLOR IMAGE
	**					= 11 RUN-LENGTH ENCODED BLACK AND WHITE IMAGE
	**	  FIELD 4 :	COLOR MAP SPECIFICATION	(5 BYTES)		
	**				4.1 : COLOR MAP ORIGIN (2 BYTES)	
	**				4.2 : COLOR MAP LENGTH (2 BYTES)	
	**				4.3 : COLOR MAP ENTRY SIZE (2 BYTES)	
	**	  FIELD 5 :	IMAGE SPECIFICATION (10 BYTES)			
	**				5.1 : X-ORIGIN OF IMAGE (2 BYTES)	
	**				5.2 : Y-ORIGIN OF IMAGE (2 BYTES)	
	**				5.3 : WIDTH OF IMAGE (2 BYTES)		
	**				5.4 : HEIGHT OF IMAGE (2 BYTES)		
	**				5.5 : IMAGE PIXEL SIZE (1 BYTE)		
	**				5.6 : IMAGE DESCRIPTOR BYTE (1 BYTE) 	
	**	  FIELD 6 :	IMAGE ID FIELD (LENGTH SPECIFIED BY FIELD 1)	
	**	  FIELD 7 :	COLOR MAP DATA (BIT WIDTH SPECIFIED BY FIELD 4.3 AND
	**				NUMBER OF COLOR MAP ENTRIES SPECIFIED IN FIELD 4.2)
	**	  FIELD 8 :	IMAGE DATA FIELD (WIDTH AND HEIGHT SPECIFIED IN
	**				FIELD 5.3 AND 5.4)				
	****************************************************************************/

	mDataOffset = 0;
	mIDLength = *(getData()+mDataOffset++);
	mColorMapType = *(getData()+mDataOffset++);
	mImageType = *(getData()+mDataOffset++);
	mColorMapIndexLo = *(getData()+mDataOffset++);
	mColorMapIndexHi = *(getData()+mDataOffset++);
	mColorMapLengthLo = *(getData()+mDataOffset++);
	mColorMapLengthHi = *(getData()+mDataOffset++);
	mColorMapDepth = *(getData()+mDataOffset++);
	mXOffsetLo = *(getData()+mDataOffset++);
	mXOffsetHi = *(getData()+mDataOffset++);
	mYOffsetLo = *(getData()+mDataOffset++);
	mYOffsetHi = *(getData()+mDataOffset++);
	mWidthLo = *(getData()+mDataOffset++);
	mWidthHi = *(getData()+mDataOffset++);
	mHeightLo = *(getData()+mDataOffset++);
	mHeightHi = *(getData()+mDataOffset++);
	mPixelSize = *(getData()+mDataOffset++);
	flags = *(getData()+mDataOffset++);
	mAttributeBits = flags & 0xf;
	mOriginRightBit = (flags & 0x10) >> 4;
	mOriginTopBit = (flags & 0x20) >> 5;
	mInterleave = (flags & 0xc0) >> 6;

	switch( mImageType )
	{
	case 0:
		// No image data included in file
		setLastError("Unable to load file.  TGA file contains no image data.");
		return FALSE;
	case 1:
		// Colormapped uncompressed
		if( 8 != mPixelSize )
		{
			setLastError("Unable to load file.  Colormapped images must have 8 bits per pixel.");
			return FALSE;
		}
		break;
	case 2:
		// Truecolor uncompressed
		break;
	case 3:
		// Monochrome uncompressed
		if( 8 != mPixelSize )
		{
			setLastError("Unable to load file.  Monochrome images must have 8 bits per pixel.");
			return FALSE;
		}
		break;
	case 9:
		// Colormapped, RLE
		break;
	case 10:
		// Truecolor, RLE
		break;
	case 11:
		// Monochrome, RLE
		if( 8 != mPixelSize )
		{
			setLastError("Unable to load file.  Monochrome images must have 8 bits per pixel.");
			return FALSE;
		}
		break;
	default:
		setLastError("Unable to load file.  Unrecoginzed TGA image type.");
		return FALSE;
	}

	// discard the ID field, if any
	if (mIDLength)
	{
		memcpy(junk, getData()+mDataOffset, mIDLength);	/* Flawfinder: ignore */
		mDataOffset += mIDLength;
	}
	
	// check to see if there's a colormap since even rgb files can have them
	S32 color_map_bytes = 0;
	if( (1 == mColorMapType) && (mColorMapDepth > 0) )
	{
		mColorMapStart = (S32(mColorMapIndexHi) << 8) + mColorMapIndexLo;
		mColorMapLength = (S32(mColorMapLengthHi) << 8) + mColorMapLengthLo;
		
		if( mColorMapDepth > 24 )
		{
			mColorMapBytesPerEntry = 4;
		}
		else
		if( mColorMapDepth > 16 )
		{
			mColorMapBytesPerEntry = 3;
		}
		else
		if( mColorMapDepth > 8 )
		{
			mColorMapBytesPerEntry = 2;
		}
		else
		{
			mColorMapBytesPerEntry = 1;
		}
		color_map_bytes = mColorMapLength * mColorMapBytesPerEntry;

		// Note: although it's legal for TGA files to have color maps and not use them
		// (some programs actually do this and use the color map for other ends), we'll
		// only allocate memory for one if _we_ intend to use it.
		if ( (1 == mImageType) || (9 == mImageType)  )
		{
			mColorMap = new U8[ color_map_bytes ];  
			if (!mColorMap)
			{
				llerrs << "Out of Memory in BOOL LLImageTGA::updateData()" << llendl;
				return FALSE;
			}
			memcpy( mColorMap, getData() + mDataOffset, color_map_bytes );	/* Flawfinder: ignore */
		}

		mDataOffset += color_map_bytes;
	}

	// heights are read as bytes to prevent endian problems
	S32 height = (S32(mHeightHi) << 8) + mHeightLo;
	S32 width = (S32(mWidthHi) << 8) + mWidthLo;

	// make sure that it's a pixel format that we understand
	S32 bits_per_pixel;
	if( mColorMap )
	{
		bits_per_pixel = mColorMapDepth;
	}
	else
	{
		bits_per_pixel = mPixelSize;
	}

	S32 components;
	switch(bits_per_pixel)
	{
	case 24:
		components = 3;
		break;
	case 32:
		components = 4;
//		Don't enforce this.  ACDSee doesn't bother to set the attributes bits correctly. Arrgh!
//		if( mAttributeBits != 8 )
//		{
//			setLastError("Unable to load file. 32 bit TGA image does not have 8 bits of alpha.");
//			return FALSE;
//		}
		mAttributeBits = 8;
		break;
	case 15:
	case 16:
		components = 3;
		mIs15Bit = TRUE;  // 16th bit is used for Targa hardware interupts and is ignored.
		break;
	case 8:
		components = 1;
		break;
	default:
		setLastError("Unable to load file. Unknown pixel size.");
		return FALSE;
	}
	setSize(width, height, components);
	
	return TRUE;
}

BOOL LLImageTGA::decode(LLImageRaw* raw_image, F32 decode_time)
{
	llassert_always(raw_image);
	
	// Check to make sure that this instance has been initialized with data
	if (!getData() || (0 == getDataSize()))
	{
		setLastError("LLImageTGA trying to decode an image with no data!");
		return FALSE;
	}

	// Copy everything after the header.

	raw_image->resize(getWidth(), getHeight(), getComponents());

	if( (getComponents() != 1) &&
		(getComponents() != 3) &&
		(getComponents() != 4) )
	{
		setLastError("TGA images with a number of components other than 1, 3, and 4 are not supported.");
		return FALSE;
	}


	if( mOriginRightBit )
	{
		setLastError("TGA images with origin on right side are not supported.");
		return FALSE;
	}

	BOOL flipped = (mOriginTopBit != 0);
	BOOL rle_compressed = ((mImageType & 0x08) != 0);

	if( mColorMap )
	{
		return decodeColorMap( raw_image, rle_compressed, flipped );
	}
	else
	{
		return decodeTruecolor( raw_image, rle_compressed, flipped );
	}
}

BOOL LLImageTGA::decodeTruecolor( LLImageRaw* raw_image, BOOL rle, BOOL flipped )
{
	BOOL success = FALSE;
	BOOL alpha_opaque = FALSE;
	if( rle )
	{

		switch( getComponents() )
		{
		case 1:
			success = decodeTruecolorRle8( raw_image );
			break;
		case 3:
			if( mIs15Bit )
			{
				success = decodeTruecolorRle15( raw_image );
			}
			else
			{
				success = decodeTruecolorRle24( raw_image );
			}
			break;
		case 4:
			success = decodeTruecolorRle32( raw_image, alpha_opaque );
			if (alpha_opaque)
			{
				// alpha was entirely opaque
				// convert to 24 bit image
				LLPointer<LLImageRaw> compacted_image = new LLImageRaw(raw_image->getWidth(), raw_image->getHeight(), 3);
				compacted_image->copy(raw_image);
				raw_image->resize(raw_image->getWidth(), raw_image->getHeight(), 3);
				raw_image->copy(compacted_image);
			}
			break;
		}
	}
	else
	{
		BOOL alpha_opaque;
		success = decodeTruecolorNonRle( raw_image, alpha_opaque );
		if (alpha_opaque && raw_image->getComponents() == 4)
		{
			// alpha was entirely opaque
			// convert to 24 bit image
			LLPointer<LLImageRaw> compacted_image = new LLImageRaw(raw_image->getWidth(), raw_image->getHeight(), 3);
			compacted_image->copy(raw_image);
			raw_image->resize(raw_image->getWidth(), raw_image->getHeight(), 3);
			raw_image->copy(compacted_image);
		}
	}
	
	if( success && flipped )
	{
		// This works because the Targa definition requires that RLE blocks never
		// encode pixels from more than one scanline.
		// (On the other hand, it's not as fast as writing separate flipped versions as 
		// we did with TruecolorNonRle.)
		raw_image->verticalFlip();
	}

	return success;
}


BOOL LLImageTGA::decodeTruecolorNonRle( LLImageRaw* raw_image, BOOL &alpha_opaque )
{
	alpha_opaque = TRUE;

	// Origin is the bottom left
	U8* dst = raw_image->getData();
	U8* src = getData() + mDataOffset;
	S32 pixels = getWidth() * getHeight();

	if (getComponents() == 4)
	{
		while( pixels-- )
		{
			// Our data is stored in RGBA.  TGA stores them as BGRA (little-endian ARGB)
			dst[0] = src[2]; // Red
			dst[1] = src[1]; // Green
			dst[2] = src[0]; // Blue
			dst[3] = src[3]; // Alpha
			if (dst[3] != 255)
			{
				alpha_opaque = FALSE;
			}
			dst += 4;
			src += 4;
		}
	}
	else if (getComponents() == 3)
	{
		if( mIs15Bit )
		{
			while( pixels-- )
			{
				decodeTruecolorPixel15( dst, src );
				dst += 3;
				src += 2;
			}
		}
		else
		{
			while( pixels-- )
			{
				dst[0] = src[2]; // Red
				dst[1] = src[1]; // Green
				dst[2] = src[0]; // Blue
				dst += 3;
				src += 3;
			}
		}
	}
	else if (getComponents() == 1)
	{
		memcpy(dst, src, pixels);	/* Flawfinder: ignore */
	}

	return TRUE;
}

void LLImageTGA::decodeColorMapPixel8( U8* dst, const U8* src )
{
	S32 index = llclamp( *src - mColorMapStart, 0, mColorMapLength - 1 );
	dst[0] = mColorMap[ index ];
}

void LLImageTGA::decodeColorMapPixel15( U8* dst, const U8* src )
{
	S32 index = llclamp( *src - mColorMapStart, 0, mColorMapLength - 1 );
	decodeTruecolorPixel15( dst, mColorMap + 2 * index );
}

void LLImageTGA::decodeColorMapPixel24( U8* dst, const U8* src )
{
	S32 index = 3 * llclamp( *src - mColorMapStart, 0, mColorMapLength - 1 );
	dst[0] = mColorMap[ index + 2 ];	// Red
	dst[1] = mColorMap[ index + 1 ];	// Green
	dst[2] = mColorMap[ index + 0 ];	// Blue
}

void LLImageTGA::decodeColorMapPixel32( U8* dst, const U8* src )
{
	S32 index = 4 * llclamp( *src - mColorMapStart, 0, mColorMapLength - 1 );
	dst[0] = mColorMap[ index + 2 ];	// Red
	dst[1] = mColorMap[ index + 1 ];	// Green
	dst[2] = mColorMap[ index + 0 ];	// Blue
	dst[3] = mColorMap[ index + 3 ];	// Alpha
}


BOOL LLImageTGA::decodeColorMap( LLImageRaw* raw_image, BOOL rle, BOOL flipped )
{
	// If flipped, origin is the top left.  Need to reverse the order of the rows.
	// Otherwise the origin is the bottom left.

	if( 8 != mPixelSize )
	{
		return FALSE;
	}

	U8* src = getData() + mDataOffset;
	U8* dst = raw_image->getData();	// start from the top
	
	void (LLImageTGA::*pixel_decoder)( U8*, const U8* );

	switch( mColorMapBytesPerEntry )
	{
		case 1:	pixel_decoder = &LLImageTGA::decodeColorMapPixel8;  break;
		case 2:	pixel_decoder = &LLImageTGA::decodeColorMapPixel15; break;
		case 3:	pixel_decoder = &LLImageTGA::decodeColorMapPixel24; break;
		case 4:	pixel_decoder = &LLImageTGA::decodeColorMapPixel32; break;
		default: llassert(0); return FALSE;
	}

	if( rle )
	{
		U8* last_dst = dst + getComponents() * (getHeight() * getWidth() - 1);
		while( dst <= last_dst )
		{
			// Read RLE block header
			U8 block_header_byte = *src;
			src++;

			U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
			if( block_header_byte & 0x80 )
			{
				// Encoded (duplicate-pixel) block
				do
				{
					(this->*pixel_decoder)( dst, src );
					dst += getComponents();
					block_pixel_count--;
				}
				while( block_pixel_count > 0 );
				src++;
			}
			else 
			{
				// Unencoded block
				do
				{
					(this->*pixel_decoder)( dst, src );
					dst += getComponents();
					src++;
					block_pixel_count--;
				}
				while( block_pixel_count > 0 );
			}
		}

		raw_image->verticalFlip();
	}
	else
	{
		S32 src_row_bytes = getWidth();
		S32 dst_row_bytes = getWidth() * getComponents();

		if( flipped )
		{
			U8* src_last_row_start = src + (getHeight() - 1) * src_row_bytes;
			src = src_last_row_start;		// start from the bottom
			src_row_bytes *= -1;
		}


		S32 i;
		S32 j;

		for( S32 row = 0; row < getHeight(); row++ )
		{
			for( i = 0, j = 0; j < getWidth(); i += getComponents(), j++ )
			{
				(this->*pixel_decoder)( dst + i, src + j );
			}

			dst += dst_row_bytes;
			src += src_row_bytes;
		}
	}

	return TRUE;
}



BOOL LLImageTGA::encode(const LLImageRaw* raw_image, F32 encode_time)
{
	llassert_always(raw_image);
	
	deleteData();

	setSize(raw_image->getWidth(), raw_image->getHeight(), raw_image->getComponents());

	// Data from header
	mIDLength = 0;		// Length of identifier string
	mColorMapType = 0;	// 0 = No Map

	// Supported: 2 = Uncompressed true color, 3 = uncompressed monochrome without colormap
	switch( getComponents() )
	{
	case 1:
		mImageType = 3;		
		break;
	case 2:	 // Interpret as intensity plus alpha
	case 3:
	case 4:
		mImageType = 2;		
		break;
	default:
		return FALSE;
	}

	// Color map stuff (unsupported)
	mColorMapIndexLo = 0;		// First color map entry (low order byte)
	mColorMapIndexHi = 0;		// First color map entry (high order byte)
	mColorMapLengthLo = 0;		// Color map length (low order byte)
	mColorMapLengthHi = 0;		// Color map length (high order byte)
	mColorMapDepth = 0;	// Size of color map entry (15, 16, 24, or 32 bits)

	// Image offset relative to origin.
	mXOffsetLo = 0;		// X offset from origin (low order byte)
	mXOffsetHi = 0;		// X offset from origin (hi order byte)
	mYOffsetLo = 0;		// Y offset from origin (low order byte)
	mYOffsetHi = 0;		// Y offset from origin (hi order byte)

	// Height and width
	mWidthLo = U8(getWidth() & 0xFF);			// Width (low order byte)
	mWidthHi = U8((getWidth() >> 8) & 0xFF);	// Width (hi order byte)
	mHeightLo = U8(getHeight() & 0xFF);			// Height (low order byte)
	mHeightHi = U8((getHeight() >> 8) & 0xFF);	// Height (hi order byte)

	S32 bytes_per_pixel;
	switch( getComponents() )
	{
	case 1:
		bytes_per_pixel = 1;		
		break;
	case 3:
		bytes_per_pixel = 3;		
		break;
	case 2:	 // Interpret as intensity plus alpha.  Store as RGBA.
	case 4:
		bytes_per_pixel = 4;		
		break;
	default:
		return FALSE;
	}
	mPixelSize = U8(bytes_per_pixel * 8);		// 8, 16, 24, 32 bits per pixel

	mAttributeBits = (4 == bytes_per_pixel) ? 8 : 0;	// 4 bits: number of attribute bits (alpha) per pixel
	mOriginRightBit = 0;	// 1 bit: origin, 0 = left, 1 = right
	mOriginTopBit = 0;	// 1 bit: origin, 0 = bottom, 1 = top
	mInterleave = 0;	// 2 bits: interleaved flag, 0 = none, 1 = interleaved 2, 2 = interleaved 4


	const S32 TGA_HEADER_SIZE = 18;
	const S32 COLOR_MAP_SIZE = 0;
	mDataOffset = TGA_HEADER_SIZE + mIDLength + COLOR_MAP_SIZE; // Offset from start of data to the actual header.

	S32 pixels = getWidth() * getHeight();
	S32 datasize = mDataOffset + bytes_per_pixel * pixels;
	U8* dst = allocateData(datasize);

	// Write header
	*(dst++) = mIDLength;		
	*(dst++) = mColorMapType;	
	*(dst++) = mImageType;		
	*(dst++) = mColorMapIndexLo;		
	*(dst++) = mColorMapIndexHi;		
	*(dst++) = mColorMapLengthLo;		
	*(dst++) = mColorMapLengthHi;		
	*(dst++) = mColorMapDepth;	
	*(dst++) = mXOffsetLo;		
	*(dst++) = mXOffsetHi;		
	*(dst++) = mYOffsetLo;		
	*(dst++) = mYOffsetHi;		
	*(dst++) = mWidthLo;		
	*(dst++) = mWidthHi;		
	*(dst++) = mHeightLo;		
	*(dst++) = mHeightHi;		
	*(dst++) = mPixelSize;		
	*(dst++) =
		((mInterleave & 3) << 5) |
		((mOriginTopBit & 1) << 4) |
		((mOriginRightBit & 1) << 3) |
		((mAttributeBits & 0xF) << 0);	

	// Write pixels
	const U8* src = raw_image->getData();
	llassert( dst == getData() + mDataOffset );
	S32 i = 0;
	S32 j = 0;
	switch( getComponents() )
	{
	case 1:
		memcpy( dst, src, bytes_per_pixel * pixels );	/* Flawfinder: ignore */
		break;

	case 2:
		while( pixels-- )
		{
			dst[i + 0] = src[j + 0];	// intensity
			dst[i + 1] = src[j + 0];	// intensity
			dst[i + 2] = src[j + 0];	// intensity
			dst[i + 3] = src[j + 1];	// alpha
			i += 4;
			j += 2;
		}
		break;

	case 3:
		while( pixels-- )
		{
			dst[i + 0] = src[i + 2];	// blue
			dst[i + 1] = src[i + 1];	// green
			dst[i + 2] = src[i + 0];	// red
			i += 3;
		}
		break;

	case 4:
		while( pixels-- )
		{
			dst[i + 0] = src[i + 2];	// blue
			dst[i + 1] = src[i + 1];	// green
			dst[i + 2] = src[i + 0];	// red
			dst[i + 3] = src[i + 3];	// alpha
			i += 4;
		}
		break;
	}
	
	return TRUE;
}

BOOL LLImageTGA::decodeTruecolorRle32( LLImageRaw* raw_image, BOOL &alpha_opaque )
{
	llassert( getComponents() == 4 );
	alpha_opaque = TRUE;

	U8* dst = raw_image->getData();
	U32* dst_pixels = (U32*) dst;

	U8* src = getData() + mDataOffset;
	U8* last_src = src + getDataSize();

	U32 rgba;
	U8* rgba_byte_p = (U8*) &rgba;

	U32* last_dst_pixel = dst_pixels + getHeight() * getWidth() - 1;
	while( dst_pixels <= last_dst_pixel )
	{
		// Read RLE block header
		
		if (src >= last_src)
			return FALSE;

		U8 block_header_byte = *src;
		src++;

		U32 block_pixel_count = (block_header_byte & 0x7F) + 1;
		if( block_header_byte & 0x80 )
		{
			// Encoded (duplicate-pixel) block

			if (src + 3 >= last_src)
				return FALSE;
			
			rgba_byte_p[0] = src[2];
			rgba_byte_p[1] = src[1];
			rgba_byte_p[2] = src[0];
			rgba_byte_p[3] = src[3];
			if (rgba_byte_p[3] != 255)
			{
				alpha_opaque = FALSE;
			}

			src += 4;
			register U32 value = rgba;
			do
			{
				*dst_pixels = value;
				dst_pixels++;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
		}
		else 
		{
			// Unencoded block
			do
			{
				if (src + 3 >= last_src)
					return FALSE;
				
				((U8*)dst_pixels)[0] = src[2];
				((U8*)dst_pixels)[1] = src[1];
				((U8*)dst_pixels)[2] = src[0];
				((U8*)dst_pixels)[3] = src[3];
				if (src[3] != 255)
				{
					alpha_opaque = FALSE;
				}
				src += 4;
				dst_pixels++;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
		}
	}

	return TRUE; 
}

BOOL LLImageTGA::decodeTruecolorRle15( LLImageRaw* raw_image )
{
	llassert( getComponents() == 3 );
	llassert( mIs15Bit );

	U8* dst = raw_image->getData();
	U8* src = getData() + mDataOffset;

	U8* last_src = src + getDataSize();
	U8* last_dst = dst + getComponents() * (getHeight() * getWidth() - 1);

	while( dst <= last_dst )
	{
		// Read RLE block header

		if (src >= last_src)
			return FALSE;

		U8 block_header_byte = *src;
		src++;

		U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
		if( block_header_byte & 0x80 )
		{
			// Encoded (duplicate-pixel) block
			do
			{
				if (src + 2 >= last_src)
					return FALSE;
				
				decodeTruecolorPixel15( dst, src );   // slow
				dst += 3;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
			src += 2;
		}
		else 
		{
			// Unencoded block
			do
			{
				if (src + 2 >= last_src)
					return FALSE;

				decodeTruecolorPixel15( dst, src );
				dst += 3;
				src += 2;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
		}
	}

	return TRUE;
}



BOOL LLImageTGA::decodeTruecolorRle24( LLImageRaw* raw_image )
{
	llassert( getComponents() == 3 );

	U8* dst = raw_image->getData();
	U8* src = getData() + mDataOffset;

	U8* last_src = src + getDataSize();
	U8* last_dst = dst + getComponents() * (getHeight() * getWidth() - 1);

	while( dst <= last_dst )
	{
		// Read RLE block header

		if (src >= last_src)
			return FALSE;
	
		U8 block_header_byte = *src;
		src++;

		U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
		if( block_header_byte & 0x80 )
		{
			// Encoded (duplicate-pixel) block
			do
			{
				if (src + 2 >= last_src)
					return FALSE;
				dst[0] = src[2];
				dst[1] = src[1];
				dst[2] = src[0];
				dst += 3;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
			src += 3;
		}
		else 
		{
			// Unencoded block
			do
			{
				if (src + 2 >= last_src)
					return FALSE;
				
				dst[0] = src[2];
				dst[1] = src[1];
				dst[2] = src[0];
				dst += 3;
				src += 3;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
		}
	}

	return TRUE;
}


BOOL LLImageTGA::decodeTruecolorRle8( LLImageRaw* raw_image )
{
	llassert( getComponents() == 1 );

	U8* dst = raw_image->getData();
	U8* src = getData() + mDataOffset;

	U8* last_src = src + getDataSize();
	U8* last_dst = dst + getHeight() * getWidth() - 1;
	
	while( dst <= last_dst )
	{
		// Read RLE block header

		if (src >= last_src)
			return FALSE;

		U8 block_header_byte = *src;
		src++;

		U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
		if( block_header_byte & 0x80 )
		{
			if (src >= last_src)
				return FALSE;
			
			// Encoded (duplicate-pixel) block
			memset( dst, *src, block_pixel_count );
			dst += block_pixel_count;
			src++;
		}
		else 
		{
			// Unencoded block
			do
			{
				if (src >= last_src)
					return FALSE;
				
				*dst = *src;
				dst++;
				src++;
				block_pixel_count--;
			}
			while( block_pixel_count > 0 );
		}
	}

	return TRUE;
}


// Decoded and process the image for use in avatar gradient masks.
// Processing happens during the decode for speed.
BOOL LLImageTGA::decodeAndProcess( LLImageRaw* raw_image, F32 domain, F32 weight )
{
	llassert_always(raw_image);
	
	// "Domain" isn't really the right word.  It refers to the width of the 
	// ramp portion of the function that relates input and output pixel values.
	// A domain of 0 gives a step function.
	// 
	//   |                      /----------------
	//  O|                     / |
	//  u|                    /  |
	//  t|                   /   |
	//	p|------------------/    |
	//  u|                  |    | 
	//  t|<---------------->|<-->|
	//	 |  "offset"         "domain"
	//   |
	// --+---Input--------------------------------
	//   |

	if (!getData() || (0 == getDataSize()))
	{
		setLastError("LLImageTGA trying to decode an image with no data!");
		return FALSE;
	}

	// Only works for unflipped monochrome RLE images
	if( (getComponents() != 1) || (mImageType != 11) || mOriginTopBit || mOriginRightBit ) 
	{
		llerrs << "LLImageTGA trying to alpha-gradient process an image that's not a standard RLE, one component image" << llendl;
		return FALSE;
	}

	raw_image->resize(getWidth(), getHeight(), getComponents());

	U8* dst = raw_image->getData();
	U8* src = getData() + mDataOffset;
	U8* last_dst = dst + getHeight() * getWidth() - 1;

	if( domain > 0 )
	{
		// Process using a look-up table (lut)
		const S32 LUT_LEN = 256;
		U8 lut[LUT_LEN];
		S32 i;

		F32 scale = 1.f / domain;
		F32 offset = (1.f - domain) * llclampf( 1.f - weight );
		F32 bias = -(scale * offset);
		
		for( i = 0; i < LUT_LEN; i++ )
		{
			lut[i] = (U8)llclampb( 255.f * ( i/255.f * scale + bias ) );
		}

		while( dst <= last_dst )
		{
			// Read RLE block header
			U8 block_header_byte = *src;
			src++;

			U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
			if( block_header_byte & 0x80 )
			{
				// Encoded (duplicate-pixel) block
				memset( dst, lut[ *src ], block_pixel_count );
				dst += block_pixel_count;
				src++;
			}
			else 
			{
				// Unencoded block
				do
				{
					*dst = lut[ *src ];
					dst++;
					src++;
					block_pixel_count--;
				}
				while( block_pixel_count > 0 );
			}
		}
	}
	else
	{
		// Process using a simple comparison agains a threshold
		const U8 threshold = (U8)(0xFF * llclampf( 1.f - weight ));

		while( dst <= last_dst )
		{
			// Read RLE block header
			U8 block_header_byte = *src;
			src++;

			U8 block_pixel_count = (block_header_byte & 0x7F) + 1;
			if( block_header_byte & 0x80 )
			{
				// Encoded (duplicate-pixel) block
				memset( dst, ((*src >= threshold) ? 0xFF : 0), block_pixel_count );
				dst += block_pixel_count;
				src++;
			}
			else 
			{
				// Unencoded block
				do
				{
					*dst = (*src >= threshold) ? 0xFF : 0;
					dst++;
					src++;
					block_pixel_count--;
				}
				while( block_pixel_count > 0 );
			}
		}
	}
	return TRUE;
}

// Reads a .tga file and creates an LLImageTGA with its data.
bool LLImageTGA::loadFile( const LLString& path )
{
	S32 len = path.size();
	if( len < 5 )
	{
		return false;
	}
	
	LLString extension = path.substr( len - 4, 4 );
	LLString::toLower(extension);
	if( ".tga" != extension )
	{
		return false;
	}
	
	LLFILE* file = LLFile::fopen(path.c_str(), "rb");	/* Flawfinder: ignore */
	if( !file )
	{
		llwarns << "Couldn't open file " << path << llendl;
		return false;
	}

	S32 file_size = 0;
	if (!fseek(file, 0, SEEK_END))
	{
		file_size = ftell(file);
		fseek(file, 0, SEEK_SET);
	}

	U8* buffer = allocateData(file_size);
	S32 bytes_read = fread(buffer, 1, file_size, file);
	if( bytes_read != file_size )
	{
		deleteData();
		llwarns << "Couldn't read file " << path << llendl;
		return false;
	}

	fclose( file );

	if( !updateData() )
	{
		llwarns << "Couldn't decode file " << path << llendl;
		deleteData();
		return false;
	}
	return true;
}