LoadTGACpp

From GPWiki

Sample code to load 8 bit indexed as well as 24 and 32 bit RGB TGA files. The code will read uncompressed and RLE encoded images.

The Load() method gets the file into memory, use the other public functions to access the image properties and data after loading.

// 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;
 }