在位图上绘制直线、图形或者文字

这是一篇讲述如何在位图上绘制直线、图形或者文字的文章。尽管这项工作相当简单，但是对一些新手来说，本文将会是一份方便的参考。

用HBITMAP进行操作

    作为第一步，我们需要一个关联背景图像的HBitmap句柄。这个句柄可以由之前的操作返回、用CreateBitmap()函数创建、或者从资源中加载，具体操作如下：

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HBITMAP hBitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINGRESOURCE(IDC_BITMAP1)); 
HBITMAP hBitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINGRESOURCE(IDC_BITMAP1));

    之后，从hBitmap里面我们可以提取一些基本属性：

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BITMAP bm;  
GetObject(hBitmap, sizeof(HBITMAP), &bm);  
long nWidth = bm.bmWidth;  
long nHeight = bm.bmHeight; 
BITMAP bm;
GetObject(hBitmap, sizeof(HBITMAP), &bm);
long nWidth = bm.bmWidth;
long nHeight = bm.bmHeight;

     现在创建一个位于内存的dc(显示上下文)，然后关联一张新的位图。

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// 初始化位图属性  
BITMAPINFO bmInfo;  
memset(&bmInfo.bmiHeader, 0, sizeof(BITMAPINFOHEADER));  
bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);  
bmInfo.bmiHeader.biWidth=width;  
bmInfo.bmiHeader.biHeight=height;  
bmInfo.bmiHeader.biPlanes=1;  
bmInfo.bmiHeader.biBitCount=24;  
 
// 创建一个临时dc, 全屏  
HDC pDC = ::GetDC(NULL);  
HDC TmpDC=CreateCompatibleDC(pDC);  
// 创建一个新的位图，然后把它选入上面的临时dc  
 
BYTE *pbase;  
HBITMAP TmpBmp=CreateDIBSection(pDC,  
    &bmInfo,DIB_RGB_COLORS,(void**)&pbase,0,0);  
HGDIOBJ TmpObj=SelectObject(TmpDC,TmpBmp); 
// 初始化位图属性
BITMAPINFO bmInfo;
memset(&bmInfo.bmiHeader, 0, sizeof(BITMAPINFOHEADER));
bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
bmInfo.bmiHeader.biWidth=width;
bmInfo.bmiHeader.biHeight=height;
bmInfo.bmiHeader.biPlanes=1;
bmInfo.bmiHeader.biBitCount=24;

// 创建一个临时dc, 全屏
HDC pDC = ::GetDC(NULL);
HDC TmpDC=CreateCompatibleDC(pDC);
// 创建一个新的位图，然后把它选入上面的临时dc

BYTE *pbase;
HBITMAP TmpBmp=CreateDIBSection(pDC,
    &bmInfo,DIB_RGB_COLORS,(void**)&pbase,0,0);
HGDIOBJ TmpObj=SelectObject(TmpDC,TmpBmp);
 

TmpDC 就是那个你可以在上面画线、图形或者字体的显示上下文。例如，下面就是绘制一个字符串到背景图像的做法：

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//draw the background  
HDC dcBmp=CreateCompatibleDC(TmpDC);  
HGDIOBJ TmpObj2 = SelectObject(dcBmp,hbitmap);  
BitBlt(TmpDC,0,0,width,height,dcBmp,0,0,SRCCOPY);  
SelectObject(TmpDC,TmpObj2);  
DeleteDC(dcBmp);  
 
//choose the font  
CFont m_Font;  
LOGFONT* m_pLF;  
m_pLF=(LOGFONT*)calloc(1,sizeof(LOGFONT));  
strncpy(m_pLF->lfFaceName,"Times New Roman",31);  
m_pLF->lfHeight=64;  
m_pLF->lfWeight=600;  
m_pLF->lfItalic=1;  
m_pLF->lfUnderline=0;  
m_Font.CreateFontIndirect(m_pLF);  
 
//select the font in the dc  
CDC dc;  
dc.Attach(TmpDC);  
CFont* pOldFont=NULL;  
if (m_Font.m_hObject)   
    pOldFont = dc.SelectObject(&m_Font);  
else   
    dc.SelectObject(GetStockObject(DEFAULT_GUI_FONT));  
 
//Set text color  
dc.SetTextColor(RGB(60,120,240));  
//Set text position;  
RECT pos = {40,40,0,0};  
//draw the text  
dc.SetBkMode(TRANSPARENT);  
dc.DrawText("Test",4,&pos,DT_CALCRECT);  
dc.DrawText("Test",4,&pos,0);  
 
//cleanup   
if (pOldFont) dc.SelectObject(pOldFont);  
m_Font.DeleteObject();  
dc.Detach();  
free(m_pLF); 
//draw the background
HDC dcBmp=CreateCompatibleDC(TmpDC);
HGDIOBJ TmpObj2 = SelectObject(dcBmp,hbitmap);
BitBlt(TmpDC,0,0,width,height,dcBmp,0,0,SRCCOPY);
SelectObject(TmpDC,TmpObj2);
DeleteDC(dcBmp);

//choose the font
CFont m_Font;
LOGFONT* m_pLF;
m_pLF=(LOGFONT*)calloc(1,sizeof(LOGFONT));
strncpy(m_pLF->lfFaceName,"Times New Roman",31);
m_pLF->lfHeight=64;
m_pLF->lfWeight=600;
m_pLF->lfItalic=1;
m_pLF->lfUnderline=0;
m_Font.CreateFontIndirect(m_pLF);

//select the font in the dc
CDC dc;
dc.Attach(TmpDC);
CFont* pOldFont=NULL;
if (m_Font.m_hObject)
    pOldFont = dc.SelectObject(&m_Font);
else
    dc.SelectObject(GetStockObject(DEFAULT_GUI_FONT));

//Set text color
dc.SetTextColor(RGB(60,120,240));
//Set text position;
RECT pos = {40,40,0,0};
//draw the text
dc.SetBkMode(TRANSPARENT);
dc.DrawText("Test",4,&pos,DT_CALCRECT);
dc.DrawText("Test",4,&pos,0);

//cleanup
if (pOldFont) dc.SelectObject(pOldFont);
m_Font.DeleteObject();
dc.Detach();
free(m_pLF);
 

 在这有两个位图句柄：hBitmap和TmpBmp。你可以绘制新老两张位图，或者用TmpBmp替换hBitmap。

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DeleteObject(TmpDC, TmpObj);  
DeleteDC(TmpDC); 
DeleteObject(TmpDC, TmpObj);
DeleteDC(TmpDC);

最后，要删除临时dc。在这儿不要删除hBitmap和TmpBmp，否者你会失去他们。

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//final cleanup  
SelectObject(TmpDC,TmpObj);  
DeleteDC(TmpDC); 

 

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/boyzk2008/archive/2009/03/28/4032082.aspx