考虑窗口具有白色背景,然后需要在上面绘制图形。
首先,在绘制图形时,希望将图形“淡入”到背景中去;撤除图形时,希望“淡出”背景。
可以参考下面函数实现这种效果。
下面的代码演示如何用调色板动画来达到淡入淡出功能。
函数一:用保留调色板项创建调色板
- <blockquote>// CreateReservedPalette<span style="white-space:pre"> </span>- Create a palette using the PC_RESERVED flag
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函数二:用给定颜色淡入图形
- // FadeIn - Draws a start color and fades the bitmap in.
- // pDC - Pointer to the device context to draw in
- // hDIB - Handle to a device-independent bitmap
- // clrStart - The start color of the bitmap
- // xDest - x-coordinate of upper-left corner of dest. rect.
- // yDest - y-coordinate of upper-left corner of dest. rect.
- // nLoops - How many loops to fade the image in
- // nDelay - Delay in milli-seconds between each loop
- //
- void FadeIn( CDC *pDC, HANDLE hDIB, COLORREF clrStart, int xDest, int yDest,
- int nLoops, int nDelay )
- {
- HPALETTE hPal;
- PALETTEENTRY peAnimate[256];
- PALETTEENTRY peOriginal[256];
- CPalette pal;
- // Create a 236 colors or less logical palette with PC_RESERVED set
- if (!(hPal = CreateReservedPalette(hDIB)))
- return;
- // The palette will be deleted when the CPalette object is destroyed
- pal.Attach( hPal );
- BITMAPINFO &bmInfo = *(LPBITMAPINFO)hDIB ;
-
- int nColors = bmInfo.bmiHeader.biClrUsed ? bmInfo.bmiHeader.biClrUsed :
- 1 << bmInfo.bmiHeader.biBitCount; int nWidth="bmInfo.bmiHeader.biWidth;" int nHeight="bmInfo.bmiHeader.biHeight;" // Obtain the original entries in the palette GetPaletteEntries(hPal, 0, nColors, (LPPALETTEENTRY)&peOriginal); // Change all the entries in the palette to the start color int clrRValue="GetRValue(clrStart);" int clrGValue="GetGValue(clrStart);" int clrBValue="GetBValue(clrStart);" for (int j="0;" j < nColors; j++) { peAnimate[j].peRed="clrRValue;" peAnimate[j].peGreen="clrGValue;" peAnimate[j].peBlue="clrBValue;" peAnimate[j].peFlags="PC_RESERVED;" } // Select the palette CPalette *pOldPalette="pDC-"SelectPalette(&pal, FALSE);
- pDC->RealizePalette();
- // We need to draw the image so that it appears as a rectangle
- // with the start color. At the same time we don't want the
- // colors to be remapped, otherwise all the pixels would remain
- // the same color. We use a memory DC to achieve this.
- CDC memDC;
- memDC.CreateCompatibleDC( pDC );
- CBitmap bmp;
- bmp.CreateCompatibleBitmap( pDC, nWidth, nHeight );
- CBitmap *pOldBitmap = memDC.SelectObject( &bmp );
- CPalette *pOldMemPalette = memDC.SelectPalette(&pal, FALSE);
- memDC.RealizePalette();
- // Draw the image to memDC
- LPVOID lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);
-
- ::SetDIBitsToDevice(memDC.m_hDC, // hDC
- 0, // XDest
- 0, // YDest
- nWidth, // nDestWidth
- nHeight, // nDestHeight
- 0, // XSrc
- 0, // YSrc
- 0, // nStartScan
- nHeight, // nNumScans
- lpDIBBits, // lpBits
- (LPBITMAPINFO)hDIB, // lpBitsInfo
- DIB_RGB_COLORS); // wUsage
- // Set the color to start color
- AnimatePalette(hPal, 0, nColors, (LPPALETTEENTRY)&peAnimate);
- // Now copy the image from the memory DC
- // Since the palettes in memDC and pDC are the same, no color mapping
- // takes place. The image will appear in the start color
- pDC->BitBlt(xDest, yDest, nWidth, nHeight, &memDC,0,0,SRCCOPY );
- // Fade in
- for( int i=1; i <= nLoops; i++ ) { for (j="0;" j < nColors; j++) { peAnimate[j].peRed="clrRValue" ((clrRValue-peOriginal[j].peRed)*i)/nLoops; peAnimate[j].peGreen="clrGValue" ((clrGValue-peOriginal[j].peGreen)*i)/nLoops; peAnimate[j].peBlue="clrBValue" ((clrBValue-peOriginal[j].peBlue)*i)/nLoops; } pal.AnimatePalette(0, nColors, (LPPALETTEENTRY)&peAnimate); // Delay... Sleep(nDelay); } // Reselect old objects into DC memDC.SelectPalette(pOldMemPalette, FALSE); memDC.SelectObject( pOldBitmap ); pDC-SelectPalette(pOldPalette, FALSE);
- }
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- // FadeOut - Draws a bitmap and fades it out to the desired end color
- // pDC - Pointer to the device context to draw in
- // hDIB - Handle to a device-independent bitmap
- // clrEnd - The final color of the bitmap
- // xDest - x-coordinate of upper-left corner of dest. rect.
- // yDest - y-coordinate of upper-left corner of dest. rect.
- // nLoops - How many loops to fade the image out.
- // nDelay - Delay in milli-seconds between each loop
- //
- void FadeOut( CDC *pDC, HANDLE hDIB, COLORREF clrEnd, int xDest, int yDest,
- int nLoops, int nDelay )
- {
- HPALETTE hPal;
- PALETTEENTRY peAnimate[256];
- PALETTEENTRY peOriginal[256];
- CPalette pal;
- // Create a 236 colors or less logical palette with PC_RESERVED set
- if (!(hPal = CreateReservedPalette(hDIB)))
- return;
- // The palette will be deleted when the CPalette object is destroyed
- pal.Attach( hPal );
- BITMAPINFO &bmInfo = *(LPBITMAPINFO)hDIB ;
-
- int nColors = bmInfo.bmiHeader.biClrUsed ? bmInfo.bmiHeader.biClrUsed :
- 1 << bmInfo.bmiHeader.biBitCount; int nWidth="bmInfo.bmiHeader.biWidth;" int nHeight="bmInfo.bmiHeader.biHeight;" // Obtain the original entries in the palette GetPaletteEntries(hPal, 0, nColors, (LPPALETTEENTRY)&peAnimate); GetPaletteEntries(hPal, 0, nColors, (LPPALETTEENTRY)&peOriginal); // Get end color values int clrRValue="GetRValue(clrEnd);" int clrGValue="GetGValue(clrEnd);" int clrBValue="GetBValue(clrEnd);" // Select the palette CPalette *pOldPalette="pDC-"SelectPalette(&pal, FALSE);
- pDC->RealizePalette();
- // Draw the image
- LPVOID lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);
-
- ::SetDIBitsToDevice(pDC->m_hDC, // hDC
- xDest, // XDest
- yDest, // YDest
- nWidth, // nDestWidth
- nHeight, // nDestHeight
- 0, // XSrc
- 0, // YSrc
- 0, // nStartScan
- nHeight, // nNumScans
- lpDIBBits, // lpBits
- (LPBITMAPINFO)hDIB, // lpBitsInfo
- DIB_RGB_COLORS); // wUsage
- // Fade out
- for( int i=1; i <= nLoops; i++ ) { for (int j="0;" j < nColors; j++) { peAnimate[j].peRed="peOriginal[j].peRed" ((peOriginal[j].peRed clrRValue)*i)/nLoops; peAnimate[j].peGreen="peOriginal[j].peGreen" ((peOriginal[j].peGreen clrGValue)*i)/nLoops; peAnimate[j].peBlue="peOriginal[j].peBlue" ((peOriginal[j].peBlue clrBValue)*i)/nLoops; } pal.AnimatePalette(0, nColors, (LPPALETTEENTRY)&peAnimate); // Delay... Sleep(nDelay); } // Reselect old objects into DC pDC-SelectPalette(pOldPalette, FALSE);
- }
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