// TGA Loader - 16/11/04 Codehead

#include <iostream>
#include <fstream>
#include <memory.h>

#define IMG_OK              0x1
#define IMG_ERR_NO_FILE     0x2
#define IMG_ERR_MEM_FAIL    0x4
#define IMG_ERR_BAD_FORMAT  0x8
#define IMG_ERR_UNSUPPORTED 0x40

class TGAImg
 {
  public:
   TGAImg();
   ~TGAImg();
   int Load(char* szFilename);
   int GetBPP();
   int GetWidth();
   int GetHeight();
   unsigned char* GetImg();       // Return a pointer to image data
   unsigned char* GetPalette();   // Return a pointer to VGA palette

  private:
   short int iWidth,iHeight,iBPP;
   unsigned long lImageSize;
   char bEnc;
   unsigned char *pImage, *pPalette, *pData;
   
   // Internal workers
   int ReadHeader();
   int LoadRawData();
   int LoadTgaRLEData();
   int LoadTgaPalette();
   void BGRtoRGB();
   void FlipImg();
 };


TGAImg::TGAImg()
 { 
  pImage=pPalette=pData=NULL;
  iWidth=iHeight=iBPP=bEnc=0;
  lImageSize=0;
 }


TGAImg::~TGAImg()
 {
  if(pImage)
   {
    delete [] pImage;
    pImage=NULL;
   }

  if(pPalette)
   {
    delete [] pPalette;
    pPalette=NULL;
   }

  if(pData)
   {
    delete [] pData;
    pData=NULL;
   }
 }


int TGAImg::Load(char* szFilename)
 {
  using namespace std;
  ifstream fIn;
  unsigned long ulSize;
  int iRet;

  // Clear out any existing image and palette
   if(pImage)
    {
     delete [] pImage;
     pImage=NULL;
    }

   if(pPalette)
    {
     delete [] pPalette;
     pPalette=NULL;
    }

  // Open the specified file
  fIn.open(szFilename,ios::binary);
    
   if(fIn==NULL)
    return IMG_ERR_NO_FILE;

  // Get file size
  fIn.seekg(0,ios_base::end);
  ulSize=fIn.tellg();
  fIn.seekg(0,ios_base::beg);

  // Allocate some space
  // Check and clear pDat, just in case
   if(pData)
    delete [] pData; 

  pData=new unsigned char[ulSize];

   if(pData==NULL)
    {
     fIn.close();
     return IMG_ERR_MEM_FAIL;
    }

  // Read the file into memory
  fIn.read((char*)pData,ulSize);

  fIn.close();

  // Process the header
  iRet=ReadHeader();

   if(iRet!=IMG_OK)
    return iRet;

   switch(bEnc)
    {
     case 1: // Raw Indexed
      {
       // Check filesize against header values
        if((lImageSize+18+pData[0]+768)>ulSize)
         return IMG_ERR_BAD_FORMAT;

       // Double check image type field
        if(pData[1]!=1)
         return IMG_ERR_BAD_FORMAT;

       // Load image data
       iRet=LoadRawData();
        if(iRet!=IMG_OK)
         return iRet;

       // Load palette
       iRet=LoadTgaPalette();
        if(iRet!=IMG_OK)
         return iRet;

       break;
      }

     case 2: // Raw RGB
      {
       // Check filesize against header values
        if((lImageSize+18+pData[0])>ulSize)
         return IMG_ERR_BAD_FORMAT;

       // Double check image type field
        if(pData[1]!=0)
         return IMG_ERR_BAD_FORMAT;

       // Load image data
       iRet=LoadRawData();
        if(iRet!=IMG_OK)
         return iRet;

       BGRtoRGB(); // Convert to RGB
       break;
      }

     case 9: // RLE Indexed
      {
       // Double check image type field
        if(pData[1]!=1)
         return IMG_ERR_BAD_FORMAT;

       // Load image data
       iRet=LoadTgaRLEData();
        if(iRet!=IMG_OK)
         return iRet;

       // Load palette
       iRet=LoadTgaPalette();
        if(iRet!=IMG_OK)
         return iRet;

       break;
      }
 
     case 10: // RLE RGB
      {
       // Double check image type field
        if(pData[1]!=0)
         return IMG_ERR_BAD_FORMAT;

       // Load image data
       iRet=LoadTgaRLEData();
        if(iRet!=IMG_OK)
         return iRet;

       BGRtoRGB(); // Convert to RGB
       break;
      }

     default:
      return IMG_ERR_UNSUPPORTED;
    }

  // Check flip bit
   if((pData[17] & 0x20)==0) 
     FlipImg();

  // Release file memory
  delete [] pData;
  pData=NULL;

  return IMG_OK;
 }


int TGAImg::ReadHeader() // Examine the header and populate our class attributes
 {
  short ColMapStart,ColMapLen;
  short x1,y1,x2,y2;

   if(pData==NULL)
    return IMG_ERR_NO_FILE;

   if(pData[1]>1)    // 0 (RGB) and 1 (Indexed) are the only types we know about
    return IMG_ERR_UNSUPPORTED;

   bEnc=pData[2];     // Encoding flag  1 = Raw indexed image
                      //                2 = Raw RGB
                      //                3 = Raw greyscale
                      //                9 = RLE indexed
                      //               10 = RLE RGB
                      //               11 = RLE greyscale
                      //               32 & 33 Other compression, indexed

    if(bEnc>11)       // We don't want 32 or 33
     return IMG_ERR_UNSUPPORTED;


  // Get palette info
  memcpy(&ColMapStart,&pData[3],2);
  memcpy(&ColMapLen,&pData[5],2);

  // Reject indexed images if not a VGA palette (256 entries with 24 bits per entry)
   if(pData[1]==1) // Indexed
    {
     if(ColMapStart!=0 || ColMapLen!=256 || pData[7]!=24)
      return IMG_ERR_UNSUPPORTED;
    }

  // Get image window and produce width & height values
  memcpy(&x1,&pData[8],2);
  memcpy(&y1,&pData[10],2);
  memcpy(&x2,&pData[12],2);
  memcpy(&y2,&pData[14],2);

  iWidth=(x2-x1);
  iHeight=(y2-y1);

   if(iWidth<1 || iHeight<1)
    return IMG_ERR_BAD_FORMAT;

  // Bits per Pixel
  iBPP=pData[16];

  // Check flip / interleave byte
   if(pData[17]>32) // Interleaved data
    return IMG_ERR_UNSUPPORTED;

  // Calculate image size
  lImageSize=(iWidth * iHeight * (iBPP/8));

  return IMG_OK;
 }


int TGAImg::LoadRawData() // Load uncompressed image data
 {
  short iOffset;
 
   if(pImage) // Clear old data if present
    delete [] pImage;

  pImage=new unsigned char[lImageSize];

   if(pImage==NULL)
    return IMG_ERR_MEM_FAIL;

  iOffset=pData[0]+18; // Add header to ident field size

   if(pData[1]==1) // Indexed images
    iOffset+=768;  // Add palette offset

   memcpy(pImage,&pData[iOffset],lImageSize);

  return IMG_OK;
 }


int TGAImg::LoadTgaRLEData() // Load RLE compressed image data
 {
  short iOffset,iPixelSize;
  unsigned char *pCur;
  unsigned long Index=0;
  unsigned char bLength,bLoop;

  // Calculate offset to image data
  iOffset=pData[0]+18;

  // Add palette offset for indexed images
   if(pData[1]==1)
    iOffset+=768; 

  // Get pixel size in bytes
  iPixelSize=iBPP/8;

  // Set our pointer to the beginning of the image data
  pCur=&pData[iOffset];

  // Allocate space for the image data
   if(pImage!=NULL)
    delete [] pImage;

  pImage=new unsigned char[lImageSize];

   if(pImage==NULL)
    return IMG_ERR_MEM_FAIL;

  // Decode
   while(Index<lImageSize) 
    {
      if(*pCur & 0x80) // Run length chunk (High bit = 1)
       {
        bLength=*pCur-127; // Get run length
        pCur++;            // Move to pixel data  

        // Repeat the next pixel bLength times
         for(bLoop=0;bLoop!=bLength;++bLoop,Index+=iPixelSize)
          memcpy(&pImage[Index],pCur,iPixelSize);
  
        pCur+=iPixelSize; // Move to the next descriptor chunk
       }
      else // Raw chunk
       {
        bLength=*pCur+1; // Get run length
        pCur++;          // Move to pixel data

        // Write the next bLength pixels directly
         for(bLoop=0;bLoop!=bLength;++bLoop,Index+=iPixelSize,pCur+=iPixelSize)
          memcpy(&pImage[Index],pCur,iPixelSize);
       }
    }
 
  return IMG_OK;
 }


int TGAImg::LoadTgaPalette() // Load a 256 color palette
 {
  unsigned char bTemp;
  short iIndex,iPalPtr;
  
   // Delete old palette if present
   if(pPalette)
    {
     delete [] pPalette;
     pPalette=NULL;
    }

  // Create space for new palette
  pPalette=new unsigned char[768];

   if(pPalette==NULL)
    return IMG_ERR_MEM_FAIL;

  // VGA palette is the 768 bytes following the header
  memcpy(pPalette,&pData[pData[0]+18],768);

  // Palette entries are BGR ordered so we have to convert to RGB
   for(iIndex=0,iPalPtr=0;iIndex!=256;++iIndex,iPalPtr+=3)
    {
     bTemp=pPalette[iPalPtr];               // Get Blue value
     pPalette[iPalPtr]=pPalette[iPalPtr+2]; // Copy Red to Blue
     pPalette[iPalPtr+2]=bTemp;             // Replace Blue at the end
    }

  return IMG_OK;
 }


void TGAImg::BGRtoRGB() // Convert BGR to RGB (or back again)
 {
  unsigned long Index,nPixels;
  unsigned char *bCur;
  unsigned char bTemp;
  short iPixelSize;

  // Set ptr to start of image
  bCur=pImage;

  // Calc number of pixels
  nPixels=iWidth*iHeight;

  // Get pixel size in bytes
  iPixelSize=iBPP/8;

   for(Index=0;Index!=nPixels;Index++)  // For each pixel
    {
     bTemp=*bCur;      // Get Blue value
     *bCur=*(bCur+2);  // Swap red value into first position
     *(bCur+2)=bTemp;  // Write back blue to last position

     bCur+=iPixelSize; // Jump to next pixel
    }

 }


void TGAImg::FlipImg() // Flips the image vertically (Why store images upside down?)
 {
  unsigned char bTemp;
  unsigned char *pLine1, *pLine2;
  int iLineLen,iIndex;
 
  iLineLen=iWidth*(iBPP/8);
  pLine1=pImage;
  pLine2=&pImage[iLineLen * (iHeight - 1)];

   for( ;pLine1<pLine2;pLine2-=(iLineLen*2))
    {
     for(iIndex=0;iIndex!=iLineLen;pLine1++,pLine2++,iIndex++)
      {
       bTemp=*pLine1;
       *pLine1=*pLine2;
       *pLine2=bTemp;       
      }
    } 

 }


int TGAImg::GetBPP() 
 {
  return iBPP;
 }


int TGAImg::GetWidth()
 {
  return iWidth;
 }


int TGAImg::GetHeight()
 {
  return iHeight;
 }


unsigned char* TGAImg::GetImg()
 {
  return pImage;
 }


unsigned char* TGAImg::GetPalette()
 {
  return pPalette;
 }