// Bmp.h
// NKU CSC 480/580 - Kirby
// ---------------------------------------------------------------------------
// A bare bones encapsulation of a 24-bit Windows .bmp file as an immutable class.
// by K. Kirby, Fall 1996; revised Fall 2004.
// ---------------------------------------------------------------------------

#include <iostream>
#include <fstream>
#include <cassert>
#include <string>
#include <stdexcept>
using namespace std ;



#ifndef _WINDEF_    
// Types - defined as in WinDef.h 
typedef int LONG ;
typedef unsigned int  DWORD ; 
typedef unsigned short WORD ;
#endif



#ifndef _WINGDI_
// Types - defined as in WinGDI.h

#pragma pack(2)  /* align structure fields on 2-byte boundaries */

typedef struct tagBITMAPFILEHEADER { // bmfh 
        WORD    bfType; 
        DWORD   bfSize; 
        WORD    bfReserved1; 
        WORD    bfReserved2; 
        DWORD   bfOffBits; 
} BITMAPFILEHEADER; 

typedef struct tagBITMAPINFOHEADER{ // bmih 
   DWORD  biSize; 
   LONG   biWidth; 
   LONG   biHeight; 
   WORD   biPlanes; 
   WORD   biBitCount ;
   DWORD  biCompression; 
   DWORD  biSizeImage; 
   LONG   biXPelsPerMeter; 
   LONG   biYPelsPerMeter; 
   DWORD  biClrUsed; 
   DWORD  biClrImportant; 
} BITMAPINFOHEADER; 

#pragma pack() /* return to default packing of structure fields*/

#endif




class Bmp
{
public:
    Bmp( const string& filename ) ;
   ~Bmp() ;

    int  getWidth()  const { return _bmih.biWidth ; }
    int  getHeight() const { return _bmih.biHeight ; } 
    void getPixel( int row, int column, unsigned char rgb[3] ) const ;
   
private:
    BITMAPFILEHEADER _bmfh ;
    BITMAPINFOHEADER _bmih ;
    int              _pixelCount ;  
    int              _imageSize ;   
    unsigned char*   _image ;       // the actual data

    // Helper- convert row and column to offset.
    int _rcToOffset( int row, int col ) const ;
} ;




inline void errorExit( const string& message )
{
    cerr << "Error: " << message << endl ;
    exit( 1 ) ;
}



inline Bmp::Bmp( const string& filename ) 
//
// Constructs a Bmp objects from a 24-bit uncompressed Windows BMP file.
// See Petzold & Yao, PROGRAMMING WINDOWS 95, pp.176-178 for file format description.
{
    // Open the .BMP file for input
    //
    ifstream infile( filename.c_str(), ios::in | ios::binary ) ;
    if ( ! infile )
        errorExit( "Cannot open file " + filename ) ;

    // Read the first header information
    //
    infile.read( (char*) &_bmfh, sizeof( BITMAPFILEHEADER ) ) ;
    unsigned char* pc= (unsigned char*) &_bmfh ;
    if ( ! ( pc[0]=='B' && pc[1]=='M' ) )
        errorExit( filename + " is not a BMP file" ) ;
    infile.read( (char*) &_bmih, sizeof( BITMAPINFOHEADER ) ) ;
   

   // Check to see if this kind of BMP file can be handled by this class
   //
   if ( sizeof( BITMAPINFOHEADER ) + sizeof( BITMAPFILEHEADER ) != _bmfh.bfOffBits ) 
        errorExit( "BMP file " + filename + " has unknown extra header" ) ;
   if ( _bmih.biCompression != 0 )
        errorExit( "BMP file " + filename + " is compressed and cannot be processed" ) ;
   if ( _bmih.biBitCount != 24 )
        errorExit( "BMP file " + filename + " is not a 24-bit color bitmap" ) ;

    // Read the image bytes into memory
    //
    int _imageSize=  _bmfh.bfSize - _bmfh.bfOffBits ;
    int _pixelCount= _bmih.biWidth * _bmih.biHeight ;
    _image= new unsigned char[ _imageSize ] ; 
    if ( ! _image )
        errorExit( "Insufficient memory to store BMP file " + filename ) ;
    infile.read( (char*) _image, _imageSize ) ;
    infile.close() ;
}



inline Bmp::~Bmp()
//
// Destroy the current Bmp object
{
    delete [] _image ;
}



inline void Bmp::getPixel( int row, int column, unsigned char rgb[3] ) const 
//
// Store red, green, blue values (0-255) at pixel in rgb[].
{
    assert( row >= 0 && row < _bmih.biHeight && column >= 0 && column < _bmih.biWidth ) ;
    
    unsigned char* ppix= _image +  _rcToOffset( row, column ) ;
    rgb[0]=  ppix[2] ;
    rgb[1]=  ppix[1] ;
    rgb[2]=  ppix[0] ;

}



inline int Bmp::_rcToOffset( int row, int column ) const
//
// Offset of start of RGB value for pixel at given row and column, from start of image bytes.
{
    int displayedBytesPerRow= _bmih.biWidth * 3 ;
    int shortfall= displayedBytesPerRow % 4 ;
    int pad= ( shortfall > 0 ) ? 4 - shortfall : 0 ;
    int rowLength= displayedBytesPerRow + pad ;
    int rowsDown= _bmih.biHeight - row - 1 ;
    return rowsDown * rowLength + 3*column ;
}


    
/*

HEADERS referred to above-- from WinGDI.h  ( # < Windows.h ).


    typedef struct tagBITMAPFILEHEADER { // bmfh 
            WORD    bfType; 
            DWORD   bfSize; 
            WORD    bfReserved1; 
            WORD    bfReserved2; 
            DWORD   bfOffBits; 
    } BITMAPFILEHEADER; 



    typedef struct tagBITMAPINFOHEADER{ // bmih 
       DWORD  biSize; 
       LONG   biWidth; 
       LONG   biHeight; 
       WORD   biPlanes; 
       WORD   biBitCount ;
       DWORD  biCompression; 
       DWORD  biSizeImage; 
       LONG   biXPelsPerMeter; 
       LONG   biYPelsPerMeter; 
       DWORD  biClrUsed; 
       DWORD  biClrImportant; 
    } BITMAPINFOHEADER; 



Example header contents for a 182x134 BMP file:

    {19778, 73986, 0, 0, 54 } 
    {40, 134, 183, 1, 24, 0, 73932, 4724, 4724, 0, 0 }
*/