C++针对bmp格式解析实例
本文实例讲述了C++针对bmp格式解析的方法，分享给大家供大家参考。具体方法如下：
写这代码时，容易出现如下错误：
1. 忘了on_wm_paint() 一直在界面上画不出来
2. 正确写法
BYTE* pBits = (BYTE*)lpBase + pbitmapFileHeader->bfOffBits;
写成了
BYTE* pBits = pbitmapFileHeader->bfOffBits;
这里主要是用了前面一篇中的CWnd框架。
.cpp源文件如下：
#include "ReadBMP.h"#include "resource.h"
#include <afxdlgs.h >
CMyApp theApp;
BOOL CMyApp::InitInstance()
{
m_pMainWnd = new CMainWindow;
m_pMainWnd->ShowWindow(m_nCmdShow);
return TRUE; //必须返回TRUE,否则不会进入消息循环，界面会直接退出
}
//CMainWindow
BEGIN_MESSAGE_MAP(CMainWindow, CWnd)
ON_WM_CREATE()
ON_WM_PAINT()
ON_COMMAND(IDC_OPEN, OnOpen)
END_MESSAGE_MAP()
//构造函数
CMainWindow::CMainWindow()
{
LPCTSTR lpszClassName = ::AfxRegisterWndClass(CS_HREDRAW|CS_VREDRAW, ::LoadCursorA(NULL, IDC_ARROW), (HBRUSH)(COLOR_3DFACE+1), theApp.LoadIcon(IDI_MAIN));
CreateEx(WS_EX_CLIENTEDGE, lpszClassName, "xxx", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL);
}
//析构函数
CMainWindow::~CMainWindow()
{
}
//消息映射函数
int CMainWindow::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
//OutputDebugString("oncreate");
CClientDC dc(this);
m_hMemDC = ::CreateCompatibleDC(dc);
m_nWidth = 0;
m_nHeight = 0;
//设置菜单
HMENU hMenu = ::LoadMenuA(theApp.m_hInstance, (LPCSTR)IDR_MENU);
::SetMenu(m_hWnd, hMenu);
return 0;
}
void CMainWindow::OnNcDestroy( )
{
delete this;
}
void CMainWindow::OnDestroy()
{
}
void CMainWindow::OnPaint()
{
CPaintDC dc(this);
::BitBlt(dc, 0, 0, m_nWidth, m_nHeight, m_hMemDC, 0, 0, SRCCOPY);
}
void CMainWindow::OnOpen()
{
CFileDialog dlg(TRUE);
if (IDOK != dlg.DoModal())
{
return;
}
HANDLE hFile = ::CreateFile(dlg.GetPathName(), GENERIC_READ , FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (INVALID_HANDLE_VALUE == hFile)
{
return;
}
HANDLE hFileMap = ::CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);
if (NULL == hFileMap)
{
return;
}
LPVOID lpBase = ::MapViewOfFile(hFileMap, FILE_MAP_READ, 0, 0, 0);
if (NULL == lpBase)
{
return;
}
//从头结构中取三个信息：1.bfOffBits位图数据在文件中的起始位置，2.m_nWidth图像的宽，3.m_nHeight图像的高
BITMAPFILEHEADER* pbitmapFileHeader;
BITMAPINFO* pbitmapInfo;
pbitmapFileHeader = (BITMAPFILEHEADER*)lpBase;
if (pbitmapFileHeader->bfType != MAKEWORD('B','M'))
{
MessageBox("not bmp");
::UnmapViewOfFile(lpBase);
::CloseHandle(hFileMap);
::CloseHandle(hFile);
}
//DWORD bfOffBits = pbitmapFileHeader->bfOffBits;
BYTE* pBits = (BYTE*)lpBase + pbitmapFileHeader->bfOffBits;
pbitmapInfo = (BITMAPINFO*)((BYTE*)lpBase + sizeof(BITMAPFILEHEADER));
m_nWidth = pbitmapInfo->bmiHeader.biWidth;
m_nHeight = pbitmapInfo->bmiHeader.biHeight;
//显示BMP文件到内存设备
//得客户区DC
CClientDC dc(this);
//创建与客户区DC兼容的位图
HBITMAP hBitmap = ::CreateCompatibleBitmap(dc, m_nWidth, m_nHeight);
if (hBitmap == 0)
{
return;
}
//位图选入内存DC
::SelectObject(m_hMemDC, hBitmap);
//图像数据放到建立的DC中
::SetDIBitsToDevice(m_hMemDC, 0, 0, m_nWidth, m_nHeight, 0, 0, 0, m_nHeight, pBits, pbitmapInfo, DIB_RGB_COLORS);
::InvalidateRect(m_hWnd, NULL, TRUE);
::DeleteObject(hBitmap);
::UnmapViewOfFile(lpBase);
::CloseHandle(hFileMap);
::CloseHandle(hFile);
}
.h头文件如下：
#include <afxwin.h>
class CMyApp:public CWinApp
{
public:
virtual BOOL InitInstance();
};
//CMainWindow
class CMainWindow:public CWnd
{
public:
CMainWindow();
~CMainWindow();
protected:
HDC m_hMemDC; //与客户区兼容的内存DC句柄
UINT m_nWidth; //BMP的宽度
UINT m_nHeight; //BMP的高度
//消息映射
afx_msg void OnNcDestroy( );
afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
afx_msg void OnDestroy( );
afx_msg void OnOpen();
afx_msg void OnPaint();
DECLARE_MESSAGE_MAP()
};
希望本文所述对大家的C++程序设计有所帮助。
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