/*
 * pixmap.C 
 * based on code from Francis S. Hill Jr., UMass, Amherst.
 */

#include "pixmap.h"

fstream inf;  // global in this file for convenience


//------------ getShort -------------
ushort getShort()
{// read a short in little-endian form
  char ic;
  ushort ip;
  inf.get(ic); ip = ic;  //first byte is little one 
  inf.get(ic);  ip |= ((ushort)ic << 8); // or in high order byte
  return ip;
}

//----------- getLong -------------
ulong getLong()
{  // get little-endian 4-byte value from file, compose along portably
  ulong ip = 0;
  char ic = 0;
  unsigned char uc = ic;
  inf.get(ic); uc = ic; ip = uc;
  inf.get(ic); uc = ic; ip |=((ulong)uc << 8);
  inf.get(ic); uc = ic; ip |=((ulong)uc << 16);
  inf.get(ic); uc = ic; ip |=((ulong)uc << 24);
  return ip;
}

//----------- RGBPixmap:: readBmpFile-----------
int RGBpixmap:: readBMPFile(string fname) 
{  // Read into memory an mRGB image from an uncompressed BMP file.
  // return 0 on failure, 1 on success
  inf.open(fname.c_str(), ios::in|ios::binary); //must read raw binary char's.
  if(!inf){ cout << " can't open file: " << fname << endl; return 0;}

  int k, row, col, numPadBytes, nBytesInRow;
  // read header information
  char ch1, ch2;
  inf.get(ch1); inf.get(ch2); // type is always 'BM'
  //cout << "file type = " << ch1 << ch2 << endl;
	
  ulong fileSize = getLong();
  ushort reserved1 = getShort();    // always 0
  ushort reserved2= getShort();     // always 0 
  ulong offBits = getLong();	    // offset to image - unreliable
  ulong headerSize = getLong();     // always 40
  ulong numCols = getLong();	    // number of columns in image
  ulong numRows = getLong();	    // number of rows in image
  ushort planes= getShort();        // always 1 
  ushort bitsPerPix = getShort();   // 8 or 24;only 24 bit case done 
  ulong compression = getLong();    // must be 0 for umcompressed 
  ulong imageSize = getLong();      // total bytes in image 
  ulong xPels = getLong();          // always 0 
  ulong yPels = getLong();          // always 0 
  ulong numLUTentries = getLong();  // 256 for 8 bit, otherwise 0 
  ulong impColors = getLong();      // always 0 
	
  if(bitsPerPix != 24) {cout << "not a 24 bit/pixelimage!\n"; inf.close(); return 0;}; // error!
  // in BMP file, pad bytes inserted at end of each row so total number is a mult. of 4
  nBytesInRow = ((3 * numCols + 3)/4) * 4; // round up 3*numCols to next mult. of 4
  numPadBytes = nBytesInRow - 3 * numCols; // need this many
  nRows = numRows; // set class's data members
  nCols = numCols;
  cout << "numRows,numCols = " << numRows << "," << numCols << endl;
  cout.flush();
  pixel = new mRGB[nRows * nCols]; //space for array in memory
  if(!pixel) return 0; // out of memory!
  long count = 0;
  char dum,r,g,b;
  
  for(row = 0; row < nRows; row++) // read pixel values
    {
      for(col = 0; col < nCols; col++)
	{
	  inf.get(b); inf.get(g); inf.get(r); // funny color order in BMP file
	  pixel[count].r = r; pixel[count].g = g; pixel[count++].b = b;
	}
      for(k = 0; k < numPadBytes ; k++) //skip over padding bytes at row's end
	inf >> dum;
    }
  inf.close();
  return 1; // success
}