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Posted 21 Jun 2006

A Complete ActiveX Web Control Tutorial

, 21 Jun 2006
This article is intended to help you get up to speed quickly with developing an ActiveX control. It will show you the basic concepts you need to know about ActiveX, such as methods, properties, and events, and how to communicate between an ActiveX control and a web page.
// PictureEx.cpp: implementation of the CPictureEx class.
// Picture displaying control with support for the following formats:
// GIF (including animated GIF87a and GIF89a), JPEG, BMP, WMF, ICO, CUR
// Written by Oleg Bykov (
// Copyright (c) 2001
// To use CPictureEx, follow these steps:
//   - place a static control on your dialog (either a text or a bitmap)
//   - change its identifier to something else (e.g. IDC_MYPIC)
//   - associate a CStatic with it using ClassWizard
//   - in your dialog's header file replace CStatic with CPictureEx
//     (don't forget to #include "PictureEx.h" and add 
//     PictureEx.h and PictureEx.cpp to your project)
//   - call one of the overloaded CPictureEx::Load() functions somewhere
//     (OnInitDialog is a good place to start)
//   - if the preceding Load() succeeded call Draw()
// You can also add the control by defining a member variable of type 
// CPictureEx, calling CPictureEx::Create (derived from CStatic), then 
// CPictureEx::Load and CPictureEx::Draw.
// By default, the control initializes its background to COLOR_3DFACE
// (see CPictureEx::PrepareDC()). You can change the background by
// calling CPictureEx::SetBkColor(COLORREF) after CPictureEx::Load().
// I decided to leave in the class the functions to write separate frames from 
// animated GIF to disk. If you want to use them, uncomment #define GIF_TRACING 
// and an appropriate section in CPictureEx::Load(HGLOBAL, DWORD). These functions 
// won't be compiled and linked to your project unless you uncomment #define GIF_TRACING,
// so you don't have to worry.
// Warning: this code hasn't been subject to a heavy testing, so
// use it on your own risk. The author accepts no liability for the 
// possible damage caused by this code.
// Version 1.0  7 Aug 2001
//              Initial release
// Version 1.1  6 Sept 2001
//              ATL version of the class
// Version 1.2  14 Oct 2001
//              - Fixed a problem with loading GIFs from resources
//                in MFC-version of the class for multi-modules apps.
//                Thanks to Ruben Avila-Carretero for finding this out.
//              - Got rid of waitable timer in ThreadAnimation()
//                Now CPictureEx[Wnd] works in Win95 too.
//                Thanks to Alex Egiazarov and Wayne King for the idea.
//              - Fixed a visual glitch of using SetBkColor.
//                Thanks to Kwangjin Lee for finding this out.
// Version 1.3  10 Nov 2001
//              - Fixed a DC leak. One DC leaked per each UnLoad()
//                (forgot to put a ReleaseDC() in the end of 
//                CPictureExWnd::PrepareDC() function).
//              - Now it is possible to set a clipping rectangle using
//                CPictureEx[Wnd]::SetPaintRect(const LPRECT) function.
//                The LPRECT parameter tells the class what portion of
//                a picture should it display. If the clipping rect is 
//                not set, the whole picture is shown.
//                Thanks to Fabrice Rodriguez for the idea.
//              - Added support for Stop/Draw. Now you can Stop() an
//                animated GIF, then Draw() it again, it will continue
//                animation from the frame it was stopped on. You can 
//                also know if a GIF is currently playing with the 
//                IsPlaying() function.
//              - Got rid of math.h and made m_bExitThread volatile. 
//                Thanks to Piotr Sawicki for the suggestion.

#if !defined(AFX_PICTUREEX_H__0EFE5DE0_7B68_4DB7_8B34_5DC634948438__INCLUDED_)
#define AFX_PICTUREEX_H__0EFE5DE0_7B68_4DB7_8B34_5DC634948438__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include <vector>

//#define GIF_TRACING  // uncomment it if you want detailed TRACEs

class CPictureEx : public CStatic

struct TFrame    // structure that keeps a single frame info
	IPicture *m_pPicture;  // pointer to the interface used for drawing
	SIZE     m_frameSize;
	SIZE     m_frameOffset;
	UINT     m_nDelay;     // delay (in 1/100s of a second)
	UINT     m_nDisposal;  // disposal method

#pragma pack(1)   // turn byte alignment on

enum GIFBlockTypes

enum ControlExtValues // graphic control extension packed field values
	GCX_PACKED_DISPOSAL,  // disposal method

enum LSDPackedValues  // logical screen descriptor packed field values

enum IDPackedValues   // image descriptor packed field values

struct TGIFHeader       // GIF header  
	char m_cSignature[3]; // Signature - Identifies the GIF Data Stream
						  // This field contains the fixed value 'GIF'
	char m_cVersion[3];	// Version number. May be one of the following:
						// "87a" or "89a"

struct TGIFLSDescriptor // Logical Screen Descriptor
	WORD m_wWidth;	// 2 bytes. Logical screen width
	WORD m_wHeight; // 2 bytes. Logical screen height

	unsigned char m_cPacked;      // packed field	

	unsigned char m_cBkIndex;     // 1 byte. Background color index
	unsigned char m_cPixelAspect; // 1 byte. Pixel aspect ratio
	inline int GetPackedValue(enum LSDPackedValues Value);

struct TGIFAppExtension // application extension block
	unsigned char m_cExtIntroducer; // extension introducer (0x21)
	unsigned char m_cExtLabel; // app. extension label (0xFF)
	unsigned char m_cBlockSize; // fixed value of 11
	char m_cAppIdentifier[8];   // application identifier
	char m_cAppAuth[3];  // application authentication code

struct TGIFControlExt // graphic control extension block
	unsigned char m_cExtIntroducer; // extension introducer (0x21)
	unsigned char m_cControlLabel;  // control extension label (0xF9)
	unsigned char m_cBlockSize; // fixed value of 4
	unsigned char m_cPacked;    // packed field
	WORD m_wDelayTime;	// delay time
	unsigned char m_cTColorIndex; // transparent color index
	unsigned char m_cBlockTerm;   // block terminator (0x00)
	inline int GetPackedValue(enum ControlExtValues Value);

struct TGIFCommentExt  // comment extension block
	unsigned char m_cExtIntroducer; // extension introducer (0x21)
	unsigned char m_cCommentLabel;  // comment extension label (0xFE)

struct TGIFPlainTextExt // plain text extension block
	unsigned char m_cExtIntroducer;  // extension introducer (0x21)
	unsigned char m_cPlainTextLabel; // text extension label (0x01)
	unsigned char m_cBlockSize; // fixed value of 12
	WORD m_wLeftPos;    // text grid left position
	WORD m_wTopPos;     // text grid top position
	WORD m_wGridWidth;  // text grid width
	WORD m_wGridHeight; // text grid height
	unsigned char m_cCellWidth;  // character cell width
	unsigned char m_cCellHeight; // character cell height
	unsigned char m_cFgColor; // text foreground color index
	unsigned char m_cBkColor; // text background color index

struct TGIFImageDescriptor // image descriptor block
	unsigned char m_cImageSeparator; // image separator byte (0x2C)
	WORD m_wLeftPos; // image left position
	WORD m_wTopPos;  // image top position
	WORD m_wWidth;   // image width
	WORD m_wHeight;  // image height
	unsigned char m_cPacked; // packed field
	inline int GetPackedValue(enum IDPackedValues Value);

#pragma pack() // turn byte alignment off

	BOOL GetPaintRect(RECT *lpRect);
	BOOL SetPaintRect(const RECT *lpRect);
	virtual ~CPictureEx();
	void Stop();   // stops animation
	void UnLoad(); // stops animation plus releases all resources

	BOOL IsGIF() const;
	BOOL IsPlaying() const;
	BOOL IsAnimatedGIF() const;
	SIZE GetSize() const;
	int GetFrameCount() const;
	COLORREF GetBkColor() const;
	void SetBkColor(COLORREF clr);

	// draws the picture (starts an animation thread if needed)
	// if an animation was previously stopped by Stop(),
	// continues it from the last displayed frame
	BOOL Draw();

	// loads a picture from a file
	// i.e. Load(_T("mypic.gif"));
	BOOL Load(LPCTSTR szFileName);

	// loads a picture from a global memory block (allocated by GlobalAlloc)
	// Warning: this function DOES NOT free the global memory, pointed to by hGlobal
	BOOL Load(HGLOBAL hGlobal, DWORD dwSize);

	// loads a picture from a program resource
	BOOL Load(LPCTSTR szResourceName,LPCTSTR szResourceType);


	void EnumGIFBlocks();
	void WriteDataOnDisk(CString szFileName, HGLOBAL hData, DWORD dwSize);
#endif // GIF_TRACING

	RECT m_PaintRect;
	SIZE m_PictureSize;
	COLORREF m_clrBackground;
	UINT m_nCurrFrame;
	UINT m_nDataSize;
	UINT m_nCurrOffset;
	UINT m_nGlobalCTSize;
	BOOL m_bIsPlaying;
	volatile BOOL m_bExitThread;
	BOOL m_bIsInitialized;
	HDC m_hMemDC;

	HDC m_hDispMemDC;
	HBITMAP m_hDispMemBM;
	HBITMAP m_hDispOldBM;

	HBITMAP m_hBitmap;
	HBITMAP m_hOldBitmap;
	HANDLE m_hThread;
	HANDLE m_hExitEvent;
	IPicture * m_pPicture;
	TGIFHeader * m_pGIFHeader;
	unsigned char * m_pRawData;
	TGIFLSDescriptor * m_pGIFLSDescriptor;
	std::vector<TFrame> m_arrFrames;

	void ThreadAnimation();
	static UINT WINAPI _ThreadAnimation(LPVOID pParam);

	int GetNextBlockLen() const;
	BOOL SkipNextBlock();
	BOOL SkipNextGraphicBlock();
	BOOL PrepareDC(int nWidth, int nHeight);
	void ResetDataPointer();
	enum GIFBlockTypes GetNextBlock() const;
	UINT GetSubBlocksLen(UINT nStartingOffset) const;
	HGLOBAL GetNextGraphicBlock(UINT *pBlockLen, UINT *pDelay, 
		SIZE *pBlockSize, SIZE *pBlockOffset, UINT *pDisposal);

	// Generated message map functions
	afx_msg void OnDestroy();
	afx_msg void OnPaint();

#endif // !defined(AFX_PICTUREEX_H__0EFE5DE0_7B68_4DB7_8B34_5DC634948438__INCLUDED_)

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About the Author

David Marcionek
Web Developer
United States United States
No Biography provided

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