图片透明原理.doc

半透明原理： 假设LCD是256色的。颜色格式为332（RGB） 显存中的每一个字节的数据对应一个象素点。 在数据写入显存之前，读取相应相素点值，然后与新的数据按一定的规则混合之后，再写入相应像素点的显存。这样主要问题关键是混合算法。 混合算法目前在游戏上常用到的算法是AlphaBlend。计算公式如下 假设一幅图象是A，另一幅透明的图象是B，那么透过B去看A，看上去的图象C就是B和A的混合图象，设B图象的透明度为alpha(取值为0-1，1为完全透明，0为完全不透明)，Alpha混合公式如下：R(C)=(1-alpha)*R(B)+alpha*R(A)G(C)=(1-alpha)*G(B)+alpha*G(A)B(C)=(1-alpha)*B(B)+alpha*B(A)R(x)、G(x)、B(x)分别指颜色x的RGB分量原色值。从上面的公式可以知道，Alpha其实是一个决定混合透明度的数值。应用Alpha混合技术，可以实现游戏中的许多特效，比如火光、烟雾、阴影、动态光源等半透明效果。uC/GUI系统分为好几个层面。简单地可以归结为：1、硬件驱动层2、基本2D图形库3、窗体层次越高，涉及的内容越多，修改的工作量就越大。 如果想修改最少的代码实现半透明功能，最好在硬件驱动层找切入口。在硬件驱动层中有个宏定义 LCD_WRITE_MEM(Off,data) *(U8*)(DC+(U32)(Off)=（data），从文档可以看到该宏定义的功能就是向显存写入像素点的值。流程如下：a、读取相应象素点值b、与新的象素点值按照混合算法转换。c、将转换结果写入显存对应位置。/设置透明度为0，完全不透明，先执行清屏。GUI_SetBkColor(GUI_WHITE);GUI_SetColor(GUI_WHITE);GUI_Clear();/填充一个方框GUI_SetColor(GUI_RED);GUI_FillRect(0,0,80,30);*这里设置透明度为80透明之后再执行GUI_SetColor(GUI_GREEN);GUI_FillRect(50,5,200,30);GUI_CONTEXTtypedef struct /* Variables in LCD module */LCD_COLORINDEX_UNION LCD;LCD_RECT ClipRect;U8 DrawMode;U8 SelLayer;U8 TextStyle;U8 TransPara;/* Variables in GL module */GUI_RECT* pClipRect_HL; /* High level clip rectangle . Speed optimization so drawing routines can optimize */U8 PenSize;U8 PenShape;U8 LineStyle;U8 FillStyle;/* Variables in GUICHAR module */const GUI_FONT GUI_UNI_PTR * pAFont;const GUI_UC_ENC_APILIST * pUC_API; /* Unicode encoding API */I16P LBorder;I16P DispPosX, DispPosY;I16P DrawPosX, DrawPosY;I16P TextMode, TextAlign;GUI_COLOR Color, BkColor; /* Required only when changing devices and for speed opt (caching) */* Variables in WM module */#if GUI_WINSUPPORTconst GUI_RECT* WM_pUserClipRect;GUI_HWIN hAWin;int xOff, yOff;#endif/* Variables in MEMDEV module (with memory devices only) */#if GUI_SUPPORT_DEVICESconst tLCDDEV_APIList* pDeviceAPI; /* function pointers only */GUI_HMEM hDevData;GUI_RECT ClipRectPrev;#endif/* Variables in Anitaliasing module */#if GUI_SUPPORT_AAconst tLCD_HL_APIList* pLCD_HL; /* Required to reroute drawing (HLine & Pixel) to the AA module */U8 AA_Factor;U8 AA_HiResEnable;#endif GUI_CONTEXT; 包含了整个系统作图的最基本信息。而且这个结构体所声明的变量GUI_Context也是硬件作图层(硬件驱动层)所唯一依赖的变量。在结构体中发现，需要增加透明度信息。 于是在结构体中增加一条：U8 BlendPara;/混合算法参数Alpha;现在来一个情景分析。1、在画图前设置该变量值。0-100之间。2、在LCD_WRITE_MEM时使用它。这样半透明和透明效果就都实现了。用2D图形库作图测试确实能实现半透明效果。再测试窗体时你会发现一个问题。在基于WM_Window的所有控件上使作半透明效果会出现问题：在反复刷新（即反复产生WM_PAINT）消息时，该窗体的颜色一直在变量，而且由浅及深或由深及浅反复变化实现AlphaBlend混合的代码.主要的算法是:r = (BYTE)(rForeground - rBackground)*delta) ALPHA) + rBackground);g = (BYTE)(gForeground - gBackground)*delta) ALPHA) + gBackground);b = (BYTE)(bForeground - bBackground)*delta) ALPHA) + bBackground);下面是具体实现。(代码可成功运行)/ 一共28 + 1个等级，0为透明，256为不透明，中间的值为半透明#define ALPHA 8#define FRAMEPENWIDTH 2 / 文本框的宽度#define FRAMECOLOR RGB(192,192,192) / 文本框的颜色#define SHADOWWIDTH 1 / 阴影的宽度（为了有立体感）#define SHADOWCOLOR RGB(0,0,0) / 阴影的颜色#define TEXTCOLOR RGB(0,0,192) / 文本的颜色/ 文本框的宽度缺省100像素，宽度、高度可以动态调整#define DEFAULTOUTPUTWIDTH 100VOID ShowTransparentText(HWND hDstWnd, / 在那个窗口透明显示DWORD Alpha, / Alpha通道值(0 Alpha 256)COLORREF crForeground, / 文本框底色LPCTSTR lpszTxt, / 文本DWORD dwDelayTime / 显示多长时间)COLORREF crBackground;BYTE r, g, b;BYTE rBackground, gBackground, bBackground;BYTE rForeground, gForeground, bForeground;INT x, y;INT nDstPosX, nDstPosY;INT nWidth, nHeight;HDC hWorkDC, hSaveDC, hDstDC;HANDLE hBitmap, hBitmap2;HFONT hf, hfSave;LOGFONT lf;RECT rect;DWORD delta;/创建文本框字体lf.lfHeight = 14;lf.lfWidth = 0;lf.lfEscapement = 0;lf.lfOrientation = 0;lf.lfWeight = FW_NORMAL; /FW_BOLDlf.lfItalic = FALSE;lf.lfUnderline = FALSE;lf.lfStrikeOut = 0;lf.lfCharSet = ANSI_CHARSET;lf.lfOutPrecision = OUT_DEFAULT_PRECIS;lf.lfClipPrecision = CLIP_DEFAULT_PRECIS;lf.lfQuality = DEFAULT_QUALITY;lf.lfPitchAndFamily = DEFAULT_PITCH | FF_SWISS;_tcscpy(lf.lfFaceName, TEXT(Tahoma);VERIFY(hf = CreateFontIndirect(&lf);hDstDC = GetDC(hDstWnd);hWorkDC = CreateCompatibleDC(hDstDC);hfSave = (HFONT)SelectObject(hWorkDC, hf);nWidth = DEFAULTOUTPUTWIDTH;nHeight = DEFAULTOUTPUTWIDTH;SetRect(&rect, 0,0,nWidth,nHeight);DrawText(hWorkDC, lpszTxt, lstrlen(lpszTxt), &rect, DT_CALCRECT|DT_LEFT|DT_WORDBREAK);/ 自画立体边框nWidth = rect.right - rect.left + (FRAMEPENWIDTH + SHADOWWIDTH) * 2;nHeight = rect.bottom - rect.top + (FRAMEPENWIDTH + SHADOWWIDTH) * 2;hBitmap = CreateCompatibleBitmap(hDstDC, nWidth, nHeight);SelectObject(hWorkDC, hBitmap);hSaveDC = CreateCompatibleDC(hDstDC);hBitmap2 = CreateCompatibleBitmap(hDstDC, nWidth, nHeight);SelectObject(hSaveDC, hBitmap2);GetClientRect(hDstWnd, &rect);nDstPosX = rect.left + (rect.right - rect.left - nWidth)/2;nDstPosY = rect.top + (rect.bottom - rect.top - nHeight)/2;BitBlt(hWorkDC, 0, 0, nWidth, nHeight, hDstDC, nDstPosX, nDstPosY, SRCCOPY);BitBlt(hSaveDC, 0, 0, nWidth, nHeight, hDstDC, nDstPosX, nDstPosY, SRCCOPY);delta = Alpha%(1ALPHA); / 假若Alpha的值操作256，取模/ 因为0 ， 256 对256取模都为0， 但是0为透明，256为不透明if(0 = delta) & (Alpha = (1ALPHA)delta = Alpha;rForeground = GetRValue(crForeground);gForeground = GetGValue(crForeground);bForeground = GetBValue(crForeground);for(y = SHADOWWIDTH + SHADOWWIDTH; y (nHeight - (SHADOWWIDTH + SHADOWWIDTH); y+)for(x = SHADOWWIDTH + SHADOWWIDTH; x ALPHA) + rBackground);g = (BYTE)(gForeground - gBackground)*delta) ALPHA) + gBackground);b = (BYTE)(bForeground - bBackground)*delta) ALPHA) + bBackground);SetPixel(hWorkDC, x, y, RGB(r,g,b);/ 由于Smartphone不提供FrameRect函数，所以自行实现该功能。/ 画出外框for(y = 0; y FRAMEPENWIDTH; y+)for(x = 0; x nWidth; x+)SetPixel(hWorkDC, x, y, FRAMECOLOR);SetPixel(hWorkDC, x, nHeight - y - 1, FRAMECOLOR);for(x = 0; x FRAMEPENWIDTH; x+)for(y = 0; y nHeight; y+)SetPixel(hWorkDC, x, y, FRAMECOLOR);SetPixel(hWorkDC, nWidth - x -1, y, FRAMECOLOR);/ 画出阴影框for(y = FRAMEPENWIDTH; y (FRAMEPENWIDTH+SHADOWWIDTH); y+)for(x = FRAMEPENWIDTH; x (nWidth - FRAMEPENWIDTH); x+)SetPixel(hWorkDC, x, y, SHADOWCOLOR);SetPixel(hWorkDC, x, nHeight - y - 1, SHADOWCOLOR);for(x = FRAMEPENWIDTH; x (FRAMEPENWIDTH+SHADOWWIDTH); x+)for(y = FRAMEPENWIDTH; y (nHeight - FRAMEPENWIDTH); y+)SetPixel(hWorkDC, x, y, SHADOWCOLOR);SetPixel(hWorkDC, nWidth - x -1, y, SHADOWCOLOR);/ 输出透明字SetRect(&rect, (FRAMEPENWIDTH+SHADOWWIDTH), (FRAMEPENWIDTH+SHADOWWIDTH), nWidth - (FRAMEPENWIDTH+SHADOWWIDTH), nHeight - (FRAMEPENWIDTH+SHADOWWIDTH);SetBkMode(hWorkDC, TRANSPARENT);SetTextColor(hWorkDC, TEXTCOLOR);DrawText(hWorkDC, lpszTxt, lstrlen(lpszTxt), &rect, DT_LEFT|DT_WORDBREAK);BitBlt(hDstDC, nDstPosX, nDstPosY, nWidth, nHeight, hWorkDC, 0, 0, SRCCOPY);DeleteObject(SelectObject(hWorkDC, hfSave);DeleteObject(hBitmap);DeleteDC(hWorkDC);/ 延迟制定时间，最好用WaitForSingleObject, 这样用户既可以终止等待，SetEvent即可/ 或者超时，即相当于Sleep功能Sleep(dwDelayTime);/ 恢复原来的背景BitBlt(hDstDC, nDstPosX, nDstPosY, nWidth, nHeight, hSaveDC, 0, 0, SRCCOPY);DeleteObject(hBitmap2);DeleteDC(hSaveDC);ReleaseDC(hDstWnd, hDstDC);/wince半透明效果的实现使用windows ce（5.0以上的版本）的一个api AlphaBlend，用法和BitBlt差不多：BLENDFUNCTION bf;bf.AlphaFormat=0;bf.BlendFlags=0;bf.BlendOp=AC_SRC_OVER;bf.SourceConstantAlpha=100;/透明度0-255AlphaBlend(hBackDC,0,70,73,20,hMaskDC,0,0,73,20,bf);可以在WindowsCE里用#include /还要在Project - setting - link 里连接上msimg32.lib/VC用AlphaBlend实现半透明位图Requirements:Windows NT/2000/XP: Included in Windows 2000 and later.Windows 95/98/Me: Included in Windows 98 and later.Header: Declared in Wingdi.h; include Windows.h.Library: Included as a resource in Msimg32.dll.示例: 1. void CTestDlg:SaveBitmap(CDC* pDC,CRect rect,CString filename)2. 3. CDC* memDC=new CDC;4. memDC-CreateCompatibleDC(pDC);5. CBitmap* bmp=new CBitmap;6. bmp-CreateCompatibleBitmap(pDC,rect.Width(),rect.Height();7. CBitmap* oldbitmap=memDC-SelectObject(bmp);8. /此时的bmp就相当于一张桌布，在memDC中画线etc都是画在这张桌布上9. if(!memDC-BitBlt(0,0,rect.Width(),rect.Height(),pDC,0,0,SRCCOPY)10. 11. AfxMessageBox(BitBlt Error!);12. return;13. 14. memDC-Ellipse(0,0,100,100);15. memDC-SelectObject(oldbitmap);16.17. BITMAPINFO bi;18. bi.bmiHeader.biSize=sizeof(bi.bmiHeader);19. bi.bmiHeader.biWidth=rect.Width();20. bi.bmiHeader.biHeight=rect.Height();21. bi.bmiHeader.biPlanes=1;22. bi.bmiHeader.biBitCount=16;23. bi.bmiHeader.biCompression=BI_RGB;24. bi.bmiHeader.biSizeImage=0;25. bi.bmiHeader.biXPelsPerMeter=