分类:
2008-10-14 14:52:38
透明位图的显示
作者:王骏
包含透明色的位图的绘制方法有多种,最简单的方法是调用现成的函数:TransparentBlt,也可以通过自己的代码实现类似TransparentBlt的功能,实现过程也有两种形式,一种是事先做一张掩码位图,另一种是动态生成掩码位图。本文将介绍动态生成掩码位图绘制具有透明区域位图的方法。
一、TransparentBlt 函数的使用
TransparentBlt 函数在Windows98/Windows2000以上版本运行,系统中需要包含 Msimg32.dll,使用时可以链接
Msimg32.lib。
Windows98下的TransparentBlt会产生资源泄漏,所以不建议在WIN98下使用该函数。
TransparentBlt函数原型如下:
BOOL TransparentBlt( HDC hdcDest, // 目标DC int nXOriginDest, // 目标X偏移 int nYOriginDest, // 目标Y偏移 int nWidthDest, // 目标宽度 int hHeightDest, // 目标高度 HDC hdcSrc, // 源DC int nXOriginSrc, // 源X起点 int nYOriginSrc, // 源Y起点 int nWidthSrc, // 源宽度 int nHeightSrc, // 源高度 UINT crTransparent // 透明色,COLORREF类型 );使用示例:
CBitmap FootballBMP; FootballBMP.LoadBitmap(IDB_FOOTBALLBMP); CDC ImageDC; ImageDC.CreateCompatibleDC(pDC); CBitmap *pOldImageBMP = ImageDC.SelectObject(&FootballBMP); TransparentBlt(pDC->m_hDC, 0, 0, 218, 199, ImageDC.m_hDC, 0, 0, 218, 199, RGB(0,0,0xff)); ImageDC.SelectObject(pOldImageBMP);二、实现TransparentBlt函数
HBITMAP hMaskBMP = CreateBitmap(nWidthDest, nHeightDest, 1, 1, NULL); // 建立单色位图 SetBkColor(hImageDC, RGB(0,0,0xff)); // 设置背景色为蓝色 BitBlt(hMaskDC, 0, 0, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCCOPY); // 拷贝到hMaskDC这样足球位图中蓝色区域在掩码位图中成了白色,其它区域为黑色,此时hMaskBMP 如下图:
SetBkColor(hImageDC, RGB(0,0,0)); SetTextColor(hImageDC, RGB(255,255,255)); BitBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND);这样,掩码位图中背景色(黑色)的区域在hImageBMP中被保留,前景色(白色)的部分变为黑色。 此时hImageBMP 如下图:
SetBkColor(hdcDest,RGB(255,255,255)); SetTextColor(hdcDest,RGB(0,0,0)); BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND);掩码中白色区域(数据与1相“与”结果不变)使背景保持不变,黑色区域变成黑色,此时背景显示如下:
BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCPAINT);这样就将足球绘制到背景上了。
void TransparentBlt2( HDC hdcDest, // 目标DC int nXOriginDest, // 目标X偏移 int nYOriginDest, // 目标Y偏移 int nWidthDest, // 目标宽度 int nHeightDest, // 目标高度 HDC hdcSrc, // 源DC int nXOriginSrc, // 源X起点 int nYOriginSrc, // 源Y起点 int nWidthSrc, // 源宽度 int nHeightSrc, // 源高度 UINT crTransparent // 透明色,COLORREF类型 ) { HBITMAP hOldImageBMP, hImageBMP = CreateCompatibleBitmap(hdcDest, nWidthDest, nHeightDest); // 创建兼容位图 HBITMAP hOldMaskBMP, hMaskBMP = CreateBitmap(nWidthDest, nHeightDest, 1, 1, NULL); // 创建单色掩码位图 HDC hImageDC = CreateCompatibleDC(hdcDest); HDC hMaskDC = CreateCompatibleDC(hdcDest); hOldImageBMP = (HBITMAP)SelectObject(hImageDC, hImageBMP); hOldMaskBMP = (HBITMAP)SelectObject(hMaskDC, hMaskBMP); // 将源DC中的位图拷贝到临时DC中 if (nWidthDest == nWidthSrc && nHeightDest == nHeightSrc) BitBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hdcSrc, nXOriginSrc, nYOriginSrc, SRCCOPY); else StretchBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hdcSrc, nXOriginSrc, nYOriginSrc, nWidthSrc, nHeightSrc, SRCCOPY); // 设置透明色 SetBkColor(hImageDC, crTransparent); // 生成透明区域为白色,其它区域为黑色的掩码位图 BitBlt(hMaskDC, 0, 0, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCCOPY); // 生成透明区域为黑色,其它区域保持不变的位图 SetBkColor(hImageDC, RGB(0,0,0)); SetTextColor(hImageDC, RGB(255,255,255)); BitBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND); // 透明部分保持屏幕不变,其它部分变成黑色 SetBkColor(hdcDest,RGB(255,255,255)); SetTextColor(hdcDest,RGB(0,0,0)); BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND); // "或"运算,生成最终效果 BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCPAINT); // 清理、恢复 SelectObject(hImageDC, hOldImageBMP); DeleteDC(hImageDC); SelectObject(hMaskDC, hOldMaskBMP); DeleteDC(hMaskDC); DeleteObject(hImageBMP); DeleteObject(hMaskBMP); }2.3 TransparentBlt的另外一个版本:TransparentBltU
bool TransparentBltU( HDC dcDest, // handle to Dest DC int nXOriginDest, // x-coord of destination upper-left corner int nYOriginDest, // y-coord of destination upper-left corner int nWidthDest, // width of destination rectangle int nHeightDest, // height of destination rectangle HDC dcSrc, // handle to source DC int nXOriginSrc, // x-coord of source upper-left corner int nYOriginSrc, // y-coord of source upper-left corner int nWidthSrc, // width of source rectangle int nHeightSrc, // height of source rectangle UINT crTransparent // color to make transparent ) { if (nWidthDest < 1) return false; if (nWidthSrc < 1) return false; if (nHeightDest < 1) return false; if (nHeightSrc < 1) return false; HDC dc = CreateCompatibleDC(NULL); HBITMAP bitmap = CreateBitmap(nWidthSrc, nHeightSrc, 1, GetDeviceCaps(dc, BITSPIXEL), NULL); if (bitmap == NULL) { DeleteDC(dc); return false; } HBITMAP oldBitmap = (HBITMAP)SelectObject(dc, bitmap); if (!BitBlt(dc, 0, 0, nWidthSrc, nHeightSrc, dcSrc, nXOriginSrc, nYOriginSrc, SRCCOPY)) { SelectObject(dc, oldBitmap); DeleteObject(bitmap); DeleteDC(dc); return false; } HDC maskDC = CreateCompatibleDC(NULL); HBITMAP maskBitmap = CreateBitmap(nWidthSrc, nHeightSrc, 1, 1, NULL); if (maskBitmap == NULL) { SelectObject(dc, oldBitmap); DeleteObject(bitmap); DeleteDC(dc); DeleteDC(maskDC); return false; } HBITMAP oldMask = (HBITMAP)SelectObject(maskDC, maskBitmap); SetBkColor(maskDC, RGB(0,0,0)); SetTextColor(maskDC, RGB(255,255,255)); if (!BitBlt(maskDC, 0,0,nWidthSrc,nHeightSrc,NULL,0,0,BLACKNESS)) { SelectObject(maskDC, oldMask); DeleteObject(maskBitmap); DeleteDC(maskDC); SelectObject(dc, oldBitmap); DeleteObject(bitmap); DeleteDC(dc); return false; } SetBkColor(dc, crTransparent); BitBlt(maskDC, 0,0,nWidthSrc,nHeightSrc,dc,0,0,SRCINVERT); SetBkColor(dc, RGB(0,0,0)); SetTextColor(dc, RGB(255,255,255)); BitBlt(dc, 0,0,nWidthSrc,nHeightSrc,maskDC,0,0,SRCAND); HDC newMaskDC = CreateCompatibleDC(NULL); HBITMAP newMask; newMask = CreateBitmap(nWidthDest, nHeightDest, 1, GetDeviceCaps(newMaskDC, BITSPIXEL), NULL); if (newMask == NULL) { SelectObject(dc, oldBitmap); DeleteDC(dc); SelectObject(maskDC, oldMask); DeleteDC(maskDC); DeleteDC(newMaskDC); DeleteObject(bitmap); DeleteObject(maskBitmap); return false; } SetStretchBltMode(newMaskDC, COLORONCOLOR); HBITMAP oldNewMask = (HBITMAP) SelectObject(newMaskDC, newMask); StretchBlt(newMaskDC, 0, 0, nWidthDest, nHeightDest, maskDC, 0, 0, nWidthSrc, nHeightSrc, SRCCOPY); SelectObject(maskDC, oldMask); DeleteDC(maskDC); DeleteObject(maskBitmap); HDC newImageDC = CreateCompatibleDC(NULL); HBITMAP newImage = CreateBitmap(nWidthDest, nHeightDest, 1, GetDeviceCaps(newMaskDC, BITSPIXEL), NULL); if (newImage == NULL) { SelectObject(dc, oldBitmap); DeleteDC(dc); DeleteDC(newMaskDC); DeleteObject(bitmap); return false; } HBITMAP oldNewImage = (HBITMAP)SelectObject(newImageDC, newImage); StretchBlt(newImageDC, 0, 0, nWidthDest, nHeightDest, dc, 0, 0, nWidthSrc, nHeightSrc, SRCCOPY); SelectObject(dc, oldBitmap); DeleteDC(dc); DeleteObject(bitmap); BitBlt( dcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, newMaskDC, 0, 0, SRCAND); BitBlt( dcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, newImageDC, 0, 0, SRCPAINT); SelectObject(newImageDC, oldNewImage); DeleteDC(newImageDC); SelectObject(newMaskDC, oldNewMask); DeleteDC(newMaskDC); DeleteObject(newImage); DeleteObject(newMask); return true; }