11.3 Programming the cDib Class

The code that defines the CDib class is found in the CDIB.CPP file, which is shown in Listing 11.8. In this file, each of the functions in the CDib class are defined.

Listing 11.8 CDIB.CPP The Implementation of the CDib Class

// CDIB.CPP: Implementation file for the DIB class.

///////////////////////////////////////////////////////////

#include "stdafx.h"

#include "cdib.h"

#include "windowsx.h"

///////////////////////////////////////////////////////////

// CDib::CDib()

///////////////////////////////////////////////////////////

CDib::CDib(const char* fileName)

{ // Load the bitmap and initialize

// the class's data members.

LoadBitmapFile(fileName);

}

///////////////////////////////////////////////////////////

// CDib::~CDib()

///////////////////////////////////////////////////////////

CDib::~CDib()

{ // Free the memory assigned to the bitmap.

GlobalFreePtr(m_pBmInfo);

}

///////////////////////////////////////////////////////////

// CDib::LoadBitmapFile()

// This function loads a DIB from disk into memory. // It also initializes the various class data members.

///////////////////////////////////////////////////////////

void CDib::LoadBitmapFile

(const char* fileName)

{ // Construct and open a file object.

CFile file(fileName, CFile::modeRead);

// Read the bitmap's file header into memory.

BITMAPFILEHEADER bmFileHeader;

file.Read((void*)&bmFileHeader, sizeof(bmFileHeader));

// Check whether the file is really a bitmap.

if (bmFileHeader.bfType != 0x4d42)

{ AfxMessageBox("Not a bitmap file");

m_pBmFileHeader = 0;

m_pBmInfo = 0;

m_pBmInfoHeader = 0;

m_pRGBTable = 0;

m_pDibBits = 0;

m_numColors = 0;

}

// If the file checks out okay, continue loading.

else

{ // Calculate the size of the DIB, which is the

// file size minus the size of the file header.

DWORD fileLength = file.GetLength(); DWORD dibSize = fileLength - sizeof(bmFileHeader);

// Allocate enough memory to fit the bitmap.

BYTE* pDib = (BYTE*)GlobalAlloc

(0, dibSize);

// Read the bitmap into memory and close the file.

file.Read((void*)pDib, dibSize);

file.Close();

// Initialize pointers to the bitmap's BITMAPINFO

// and BITMAPINFOHEADER structures.

m_pBmInfo = (LPBITMAPINFO) pDib;

m_pBmInfoHeader = (LPBITMAPINFOHEADER) pDib;

// Calculate a pointer to the bitmap's color table.

m_pRGBTable =

(RGBQUAD*)(pDib + m_pBmInfoHeader->biSize);

// Get the number of colors in the bitmap.

int m_numColors = GetDibNumColors();

// Calculate the bitmap image's size.

m_pBmInfoHeader->biSizeImage =

GetDibSizeImage();

// Make sure the biClrUsed field

// is initialized properly.

if (m_pBmInfoHeader->biClrUsed == 0)

m_pBmInfoHeader->biClrUsed = m_numColors;

// Calculate a pointer to the bitmap's actual data.

DWORD clrTableSize = m_numColors * sizeof(RGBQUAD);

m_pDibBits = pDib + m_pBmInfoHeader->biSize + clrTableSize;

}

}

///////////////////////////////////////////////////////////

// CDib::GetDibSizeImage()

//

// This function calculates and returns the size of the

// bitmap's image in bytes.

///////////////////////////////////////////////////////////

DWORD CDib::GetDibSizeImage()

{ // If the bitmap's biSizeImage field contains

// invalid information, calculate the correct size.

if (m_pBmInfoHeader->biSizeImage == 0)

{ // Get the width in bytes of a single row.

DWORD byteWidth = (DWORD) GetDibWidth();

// Get the height of the bitmap.

DWORD height = (DWORD) GetDibHeight();

// Multiply the byte width by the number of rows.

DWORD imageSize = byteWidth * height;

return imageSize;

}

// Otherwise, just return the size stored in

// the BITMAPINFOHEADER structure.

else return m_pBmInfoHeader->biSizeImage;

}

///////////////////////////////////////////////////////////

// CDib::GetDibWidth()

//

// This function returns the width in bytes of a single

// row in the bitmap.

///////////////////////////////////////////////////////////

UINT CDib::GetDibWidth()

{return (UINT) m_pBmInfoHeader->biWidth;

}

///////////////////////////////////////////////////////////

// CDib::GetDibHeight()

//

// This function returns the bitmap's height in pixels.

///////////////////////////////////////////////////////////

UINT CDib::GetDibHeight()

{return (UINT) m_pBmInfoHeader->biHeight;

}

///////////////////////////////////////////////////////////

// CDib::GetDibNumColors()

//

// This function returns the number of colors in the

// bitmap.

///////////////////////////////////////////////////////////

UINT CDib::GetDibNumColors()

{ if ((m_pBmInfoHeader->biClrUsed == 0) &&

(m_pBmInfoHeader->biBitCount < 9))

return (1 << m_pBmInfoHeader->biBitCount);

else

return (int) m_pBmInfoHeader->biClrUsed;

}

///////////////////////////////////////////////////////////

// CDib::GetDibInfoHeaderPtr()

//

// This function returns a pointer to the bitmap's

// BITMAPINFOHEADER structure.

///////////////////////////////////////////////////////////

LPBITMAPINFOHEADER CDib::GetDibInfoHeaderPtr()

{ return m_pBmInfoHeader;

}

///////////////////////////////////////////////////////////

// CDib::GetDibInfoPtr()

//

// This function returns a pointer to the bitmap's

// BITMAPINFO structure.

///////////////////////////////////////////////////////////

LPBITMAPINFO CDib::GetDibInfoPtr()

{ return m_pBmInfo;

}

///////////////////////////////////////////////////////////

// CDib::GetDibRGBTablePtr()

//

// This function returns a pointer to the bitmap's

// color table.

///////////////////////////////////////////////////////////

LPRGBQUAD CDib::GetDibRGBTablePtr()

{ return m_pRGBTable;

}

///////////////////////////////////////////////////////////

// CDib::GetDibBitsPtr()

//

// This function returns a pointer to the bitmap's

// actual image data.

///////////////////////////////////////////////////////////

BYTE* CDib::GetDibBitsPtr()

{ return m_pDibBits;

}