Bitmap usage extension library

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• Download demo project - 357 Kb
• Download compiled demo (MFC shared) - 337 Kb

Introduction

Needless to say that a bitmap is the gateway between different raster image formats and GDI image representation. Device Independent Bitmaps or DIBs are important objects that allow us to save, load and draw images without thinking of display mode in device context - independent way. OS will do its best to output them as close to original, as it is able, because DIBs contain all necessary color usage, color depth, and image resolution information. There are many, or better say, numerous classes that support DIB operations through wrapping Windows API functions. This MFC extension DLL contains such class and a bit more to make bitmap usage easier and more flexible.

Classes included

All class declarations are included in the bmpext.h header.

Device dependent bitmap (DDB) extension class CDDBDrawEx:

This class is intended for on-stack allocation and usage within the single scope, as it has no default constructor and no "real" data members, only pointers to externally defined ones.

It exposes public methods as follows:

// Inplace constructor. pDC - pointer to drawing context, pbmSrc - pointer to DDB to render

// on pDC, pbmBack - optional pointer to background bitmap, that pbmSrc to blend with during transparent draw.

CDDBDrawEx(CDC* pDC, CBitmap* pbmSrc, CBitmap* pbmBack = NULL);

// Wraps around source DDB filling on pDC within rDest rectangle.

void Fill(CRect& rDest);

// Wrapper around BitBlt API function. Blitting source bitmap to pDC into rDest rectangle.

void Draw(CRect& rDest, CPoint& pntSrc);

// Perform transparent DDB draw, assuming crMask color stands for transparent pixels

// in source DDB. It uses modified routine taken from flicker-free drawing example on

// www.codeguru.com. It uses optional pbmBack if supplied in constructor to do this flicker - free drawing.

void DrawTransparent(CRect& rDest, CPoint& pntSrc, COLORREF crMask);

// Constructs complex region from source bitmap using cTransparentColor and cTolerance

// for defining transparent (hollow) region areas. Internally, it uses modified region

// builder code by Jean-Edouard Lachand-Robert http://www.geocities.com/Paris/LeftBank/1160/resume.htm).

// It's extremely useful when playing with ::SetWindowRgn function to create windows with

// non-rectangular shape.

HRGN MakeRgn(COLORREF cTransparentColor = 0, COLORREF cTolerance = 0x101010);

DIBitmap encapsulation class CDib:

This class and the Frankenstein monster have much in common :) Part of its code was taken from samples shipped with MFC 4.0 book, partially from CodeGuru and other sources. I have modified it, put it together, and said "It's alive... ALIVE!" :)

It exposes public methods as follows:

<CODE>// Default constructor.

CDib();

// Several self-explanatory methods.

DWORD Width();
DWORD Height();
WORD  NumColors(  BITMAPINFOHEADER& bmiHeader );

// Object validation checking method.

BOOL  IsValid();

// Frees internal DIB member data, making object invalid. (IsValid returns false)

void Invalidate();

// Drawing method, automatically invokes DIB stretching.

BOOL  Draw(CDC*, CRect& rectDC, CRect& rectDIB);

// Direct DIB pixel access methods.

void SetPixel( int iX, int iY, RGBQUAD& rgbPixel );
RGBQUAD GetPixel(int iX, int iY);

// Save DIB to disk file.

DWORD Save(CFile& file);

// Read DIB from file, support resource reading. If bFromResource = TRUE,

// then it just skips DIB file marker read phase.

DWORD Read(CFile& file, BOOL bFromResource = FALSE );

// Reads DIB from resource, basing on its nResID. Internally invokes previous Read method.

DWORD ReadFromResource(UINT nResID);

// Next two methods create DDB from DIB object.

HBITMAP CreateDDBitmap(CDC* pDC);
HBITMAP CreateDDBitmap( HDC hDC );

// Tries to compress DIB first making it DDB, then changing compression attribute and

// converting it back to DIB.

BOOL Compress(CDC* pDC, BOOL bCompress );

// Assignment operator

CDib& operator = (CDib& dib);

Extension Classes Usage

CDDBDrawEx class usage:

<CODE>{
....
// CDC* pDC, CBitmap* bmImg, CRect rDest, and COLORREF crImgMask are declared and initialized elsewhere

....
// inplace construction

CDDBDrawEx ddbDrawEx(pDC, bmImg);

// Do transparent drawing

ddbDrawEx.DrawTransparent(rDest, CPoint(0), crImgMask );

// Do bitmapped fill

ddbDrawEx.Fill( rDest )
}

// Region creation. CBitmap bmSkin is declared and initialized elsewhere

{
....
CDDBDrawEx ddbDrawEx(NULL, &m_bmSkin );

return ddbDrawEx.MakeRgn( m_crTransparent, m_crTolerance );
}

CDib class usage:

<CODE>CDib dibTemp;
CDC* pDC = CDC::FromHandle( ::GetDC( NULL ) );

....
// nResID is declared and initialized elsewhere

dibTemp.ReadFromResource( nResID );
....
}

Demo project implementing these extensions also includes class template for customizing dialog frame. I'm going to describe this template in detailed review which I plan to publish in a week. It will cover the window frames customization technique and will be supplemented with couple of helper template class. That's all so far, but I will supply several useful control and animation class libs packaged as MFC extension DLL in the nearest future. Additions, corrections and suggestions are always welcomed, as I often haven't enough time to optimize my source or make it more elegant. Mail me at: gromov@eti.co.ru.