Accessing Pixel Data in a BMP

#include "Bitmap.h"
#include <iostream>
#include <fstream>

using namespace std;

//basic constructor
Bitmap::Bitmap()
{
    reset();
}

//constructor loads the bitmap when it is created
Bitmap::Bitmap(char *file)
{
    reset();
    loadBMP(file);
}

//destructor
Bitmap::~Bitmap()
{
    if(colours!=0) {
        delete[] colours;
    }
    if(data!=0) {
        delete[] data;
    }
}

//load a bitmap from a file and represent it correctly in memory
bool Bitmap::loadBMP(char *file)
{
    FILE *in;                  //file stream for reading
    char *tempData;       //temp storage for image data
    int numColours;            //total available colours
    
    

    loaded=false;
    if(colours!=0)
        delete[] colours;
    
    if(data!=0)
        delete[] data;
    
    //open the file for reading in binary mode
    in=fopen(file,"rb");

    //if the file does not exist return in error
    if(in==NULL)
    {
        error="File not found";
        cout<<error<<endl;
        fclose(in);
        return false;
    }

    //read in the entire BITMAPFILEHEADER
    fread(&bmfh,sizeof(BitmapFileHeader),1,in);
	cout<<"sizeof(BitmapFileHeader)="<<sizeof(BitmapFileHeader)<<endl;
    
    //check for the magic number that says this is a bitmap
    if(bmfh.bfType!=BITMAP_MAGIC_NUMBER)
    {
        error="File is not in DIB format";
        cout<<error<<endl;
        fclose(in);
        return false;
    }

    //read in the entire BITMAPINFOHEADER
    fread(&bmih,sizeof(BitmapInfoHeader),1,in);
	cout<<"sizeof(BitmapInfoHeader)="<<sizeof(BitmapInfoHeader)<<endl;

    width=bmih.biWidth;
    height=bmih.biHeight;
    bpp=bmih.biBitCount;
	cout<<"biBitCount      ="<<bmih.biBitCount<<endl;
	cout<<"biClrImportant  ="<<bmih.biClrImportant<<endl;
	cout<<"biClrUsed       ="<<bmih.biClrUsed<<endl;
	cout<<"biCompression   ="<<bmih.biCompression<<endl;
	cout<<"biHeight        ="<<bmih.biHeight<<endl;
	cout<<"biPlanes        ="<<bmih.biPlanes<<endl;
	cout<<"biSize          ="<<bmih.biSize<<endl;
	cout<<"biSizeImage     ="<<bmih.biSizeImage<<endl;
	cout<<"biWidth         ="<<bmih.biWidth <<endl;
	cout<<"biXPelsPerMeter ="<<bmih.biXPelsPerMeter<<endl;
	cout<<"biYPelsPerMeter ="<<bmih.biYPelsPerMeter<<endl;
	cout<<"bpp             ="<<bpp<<endl;

    //calculate the size of the image data with padding
    dataSize=(width*height*(unsigned int)(bmih.biBitCount/8.0));

    //calculate the number of available colours
    numColours=1<<bmih.biBitCount;
    cout<<"Number of available colors = "<<numColours<<endl;

    //if the bitmap is not 8 bits per pixel or more return in error
    if(bpp<8)
    {
        error="File is not 8 or 24 bits per pixel";
        cout<<error<<endl;
        fclose(in);
        return false;
    }

    //load the palette for 8 bits per pixel
    if(bpp==8)
    {
    	colours=new RGBQuad[numColours];
    	fread(&colours,sizeof(RGBQuad),numColours,in);
    }

    //set up the temporary buffer for the image data
    tempData=new char[dataSize];

    //exit if there is not enough memory
    if(tempData==NULL)
    {
        error="Not enough memory to allocate a temporary buffer";
        cout<<error<<endl;
        fclose(in);
        return false;
    }

    //read in the entire image
    fread(tempData,sizeof(tempData),dataSize,in);
    fclose(in);

    //calculate the witdh of the final image in bytes
    byteWidth=padWidth=(int)((float)width*(float)bpp/8.0);

    //adjust the width for padding as necessary
    while(padWidth%4!=0)
    {
        padWidth++;
    }

    
    //change format from GBR to RGB
    if(bpp==8)
    {
    	loaded=convert8(tempData);
    	
   	}
    else if(bpp==24) {
    	loaded=convert24(tempData);
    	
   	}
   	
   	
    
    //clean up memory
    delete[] tempData;

    //bitmap is now loaded
    error="Bitmap loaded";
    cout<<error<<endl;
    
    
    //return success
    return loaded;
}

//function to set the inital values
void Bitmap::reset(void) {
    loaded=false;
    colours=0;
    data=0;
    error="";
}

bool Bitmap::convert24(char* tempData) {
	int offset,diff;
    
    
	diff=width*height*RGB_BYTE_SIZE;
    
    //allocate the buffer for the final image data
    data=new char[diff];

    //exit if there is not enough memory
    if(data==NULL)
    {
        error="Not enough memory to allocate an image buffer";
        cout<<error<<endl;
        delete[] data;
        return false;
    }
    
    if(height>0)
    {
        offset=padWidth-byteWidth;
        //count backwards so you start at the front of the image
        for(int i=0;i<dataSize;i+=3)
        {
            //jump over the padding at the start of a new line
            if((i+1)%padWidth==0)
                i+=offset;
            
            //transfer the data
            *(data+i+2)=*(tempData+i);
            *(data+i+1)=*(tempData+i+1);
            *(data+i)=*(tempData+i+2);
            
            
        }
        
    }
    //image parser for a forward image
    else
    {
        offset=padWidth-byteWidth;
        int j=dataSize-3;
        //count backwards so you start at the front of the image
		for(int i=0;i<dataSize;i+=3)
        {
            //jump over the padding at the start of a new line
            if((i+1)%padWidth==0)
                i+=offset;
            
            //transfer the data
            *(data+j+2)=*(tempData+i);
            *(data+j+1)=*(tempData+i+1);
            *(data+j)=*(tempData+i+2);
            j-=3;
        }
    }
    
    return true;
}

bool Bitmap::convert8(char* tempData) {
	int offset,diff;
	bool write;
    char ans8='y', fileSave[100];
    
	diff=width*height*RGB_BYTE_SIZE;
    
    //allocate the buffer for the final image data
    data=new char[diff];

    //exit if there is not enough memory
    if(data==NULL)
    {
        error="Not enough memory to allocate an image buffer";
        cout<<error<<endl;
        delete[] data;
        return false;
    }

    if(height>0)
    {
        offset=padWidth-byteWidth;
        int j=0;
        //count backwards so you start at the front of the image
        for(int i=0;i<dataSize*RGB_BYTE_SIZE;i+=3)
        {
            //jump over the padding at the start of a new line
            if((i+1)%padWidth==0)
                i+=offset;
            
            //transfer the data
            *(data+i)=colours[*(tempData+j)].rgbRed;
            *(data+i+1)=colours[*(tempData+j)].rgbGreen;
            *(data+i+2)=colours[*(tempData+j)].rgbBlue;
            j++;
        }
    }

    //image parser for a forward image
    else {
        offset=padWidth-byteWidth;
        int j=dataSize-1;
        //count backwards so you start at the front of the image
        for(int i=0;i<dataSize*RGB_BYTE_SIZE;i+=3)
        {
            //jump over the padding at the start of a new line
            if((i+1)%padWidth==0)
                i+=offset;
            
            //transfer the data
            *(data+i)=colours[*(tempData+j)].rgbRed;
            *(data+i+1)=colours[*(tempData+j)].rgbGreen;
            *(data+i+2)=colours[*(tempData+j)].rgbBlue;
            j--;
        }
    }
    
    return true;
}

int main()
{
    char path[100],ans='y', fileSave[100];
    cout<<"Enter the file name: ";
    cin>>path;
    Bitmap bmp(path);
    cout<<"Is this ok?";
    cin>>ans;
}