Desktop Calendar
3.80/5 (21 votes)
Mar 5, 2004
85036
2339
A nice desktop calendar that sits on your desktop.
Introduction
This article describes a simple calendar that sits on your desktop. I have created this application to just study about alpha blending, desktop wallpapers, and how a device context can be saved as a bitmap. I am planning to make a more refined version including a time scheduler and reminder also.
Using the code
Alpha Blending
HBITMAP Create24BPPDIBSection(HDC hDC, int iWidth, int iHeight) { BITMAPINFO bmi; HBITMAP hbm; LPBYTE pBits; // Initialize header to 0s. ZeroMemory(&bmi, sizeof(bmi)); // Fill out the fields you care about. bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER); bmi.bmiHeader.biWidth = iWidth; bmi.bmiHeader.biHeight = iHeight; bmi.bmiHeader.biPlanes = 1; bmi.bmiHeader.biBitCount = 24; bmi.bmiHeader.biCompression = BI_RGB; // Create the surface. hbm = CreateDIBSection(hDC, &bmi, DIB_RGB_COLORS,(void **)&pBits, NULL, 0); return(hbm); } BOOL BitmapsCompatible(LPBITMAP lpbm1, LPBITMAP lpbm2) { if (lpbm1->bmBitsPixel != lpbm2->bmBitsPixel) return FALSE; if (lpbm1->bmPlanes != lpbm2->bmPlanes) return FALSE; if (lpbm1->bmWidth != lpbm2->bmWidth) return FALSE; if (lpbm1->bmHeight != lpbm2->bmHeight) return FALSE; return TRUE; } BOOL BlendImages(HBITMAP hbmSrc1, HBITMAP hbmSrc2, HBITMAP hbmDst, DWORD dwWeight1) { BITMAP bmSrc1, bmSrc2, bmDst; RGBTRIPLE *lprgbSrc1, *lprgbSrc2, *lprgbDst; DWORD dwWidthBytes, dwWeight2; int x, y; // Only values between 0 and 255 are valid. if (dwWeight1 > 255) return FALSE; // Get weighting value for second source image. dwWeight2 = 255-dwWeight1; // Get information about the surfaces you were passed. if (!GetObject(hbmSrc1, sizeof(BITMAP), &bmSrc1)) return FALSE; if (!GetObject(hbmSrc2, sizeof(BITMAP), &bmSrc2)) return FALSE; if (!GetObject(hbmDst, sizeof(BITMAP), &bmDst)) return FALSE; // Make sure you have data that meets your requirements. if (!BitmapsCompatible(&bmSrc1, &bmSrc2)) return FALSE; if (!BitmapsCompatible(&bmSrc1, &bmDst)) return FALSE; if (bmSrc1.bmBitsPixel != 24) return FALSE; if (bmSrc1.bmPlanes != 1) return FALSE; if (!bmSrc1.bmBits || !bmSrc2.bmBits || !bmDst.bmBits) return FALSE; dwWidthBytes = bmDst.bmWidthBytes; // Initialize the surface pointers. lprgbSrc1 = (RGBTRIPLE *)bmSrc1.bmBits; lprgbSrc2 = (RGBTRIPLE *)bmSrc2.bmBits; lprgbDst = (RGBTRIPLE *)bmDst.bmBits; for (y=0; y<bmDst.bmHeight; y++) { for (x=0; x<bmDst.bmWidth; x++) { lprgbDst[x].rgbtRed = (BYTE)((((DWORD)lprgbSrc1[x].rgbtRed * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtRed * dwWeight2)) >> 8); lprgbDst[x].rgbtGreen = (BYTE)((((DWORD)lprgbSrc1[x].rgbtGreen * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtGreen * dwWeight2)) >> 8); lprgbDst[x].rgbtBlue = (BYTE)((((DWORD)lprgbSrc1[x].rgbtBlue * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtBlue * dwWeight2)) >> 8); } // Move to next scan line. lprgbSrc1 = (RGBTRIPLE *)((LPBYTE)lprgbSrc1 + dwWidthBytes); lprgbSrc2 = (RGBTRIPLE *)((LPBYTE)lprgbSrc2 + dwWidthBytes); lprgbDst = (RGBTRIPLE *)((LPBYTE)lprgbDst + dwWidthBytes); } return TRUE; } BOOL DoAlphaBlend( HDC hdcDest, // Handle to destination DC. int nXOriginDest, // X-coord of upper-left corner. int nYOriginDest, // Y-coord of upper-left corner. int nWidthDest, // Destination width. int nHeightDest, // Destination height. HDC hdcSrc, // Handle to source DC. int nXOriginSrc, // X-coord of upper-left corner. int nYOriginSrc, // Y-coord of upper-left corner. int nWidthSrc, // Source width. int nHeightSrc, // Source height. DWORD dwSourceWeight) // Source weighting (between 0 and 255). { HDC hdcSrc1 = NULL; HDC hdcSrc2 = NULL; HDC hdcDst = NULL; HBITMAP hbmSrc1 = NULL; HBITMAP hbmSrc2 = NULL; HBITMAP hbmDst = NULL; BOOL bReturn; // Create surfaces for sources and destination images. hbmSrc1 = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmSrc1) goto HANDLEERROR; hbmSrc2 = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmSrc2) goto HANDLEERROR; hbmDst = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmDst) goto HANDLEERROR; // Create HDCs to hold our surfaces. hdcSrc1 = CreateCompatibleDC(hdcDest); if (!hdcSrc1) goto HANDLEERROR; hdcSrc2 = CreateCompatibleDC(hdcDest); if (!hdcSrc2) goto HANDLEERROR; hdcDst = CreateCompatibleDC(hdcDest); if (!hdcDst) goto HANDLEERROR; // Prepare the surfaces for drawing. SelectObject(hdcSrc1, hbmSrc1); SelectObject(hdcSrc2, hbmSrc2); SelectObject(hdcDst, hbmDst); SetStretchBltMode(hdcSrc1, COLORONCOLOR); SetStretchBltMode(hdcSrc2, COLORONCOLOR); // Capture a copy of the source area. if (!StretchBlt(hdcSrc1, 0,0,nWidthDest,nHeightDest, hdcSrc, nXOriginSrc, nYOriginSrc, nWidthSrc, nHeightSrc, SRCCOPY)) goto HANDLEERROR; // Capture a copy of the destination area. if (!StretchBlt(hdcSrc2, 0,0,nWidthDest,nHeightDest, hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, SRCCOPY)) goto HANDLEERROR; // Blend the two source areas to create the destination image. bReturn = BlendImages(hbmSrc1, hbmSrc2, hbmDst, dwSourceWeight); // Clean up objects you do not need any longer. // You cannot delete an object that's selected into an // HDC so delete the HDC first. DeleteDC(hdcSrc1); DeleteDC(hdcSrc2); DeleteObject(hbmSrc1); DeleteObject(hbmSrc2); // Display the blended (destination) image to the target HDC. if (bReturn) { BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hdcDst, 0,0, SRCCOPY); } // Clean up the rest of the objects you created. DeleteDC(hdcDst); DeleteObject(hbmDst); return bReturn; HANDLEERROR: if (hdcSrc1) DeleteDC(hdcSrc1); if (hdcSrc2) DeleteDC(hdcSrc2); if (hdcDst) DeleteDC(hdcDst); if (hbmSrc1) DeleteObject(hbmSrc1); if (hbmSrc2) DeleteObject(hbmSrc2); if (hbmDst) DeleteObject(hbmDst); return FALSE; }
Save Device Context into an uncompressed bitmap
// Function to save bitmap BOOL SaveBitmap(HDC hDC,HBITMAP hBitmap,CString szPath) { FILE * fp= NULL; fp = fopen(szPath.GetBuffer(1),"wb"); if(fp == NULL) return false; BITMAP Bm; BITMAPINFO BitInfo; ZeroMemory(&BitInfo, sizeof(BITMAPINFO)); BitInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER); BitInfo.bmiHeader.biBitCount = 0; if(!::GetDIBits(hDC, hBitmap, 0, 0, NULL, &BitInfo, DIB_RGB_COLORS)) return (false); Bm.bmHeight = BitInfo.bmiHeader.biHeight; Bm.bmWidth = BitInfo.bmiHeader.biWidth; BITMAPFILEHEADER BmHdr; BmHdr.bfType = 0x4d42; // 'BM' WINDOWS_BITMAP_SIGNATURE BmHdr.bfSize = (((3 * Bm.bmWidth + 3) & ~3) * Bm.bmHeight) + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER); BmHdr.bfReserved1 = BmHdr.bfReserved2 = 0; BmHdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER); BitInfo.bmiHeader.biCompression = 0; // Writing Bitmap File Header //// fwrite(&BmHdr,sizeof(BITMAPFILEHEADER),1,fp); fwrite(&BitInfo.bmiHeader,sizeof(BITMAPINFOHEADER),1,fp); BYTE *pData = new BYTE[BitInfo.bmiHeader.biSizeImage + 5]; if(!::GetDIBits(hDC, hBitmap, 0, Bm.bmHeight, pData, &BitInfo, DIB_RGB_COLORS)) return (false); if(pData != NULL) fwrite(pData,1,BitInfo.bmiHeader.biSizeImage,fp); fclose(fp); delete (pData); return (true); } // here is how to use the above function //Get the device context HDC hDC = ::GetDC(hWnd); // Create a memory device context HDC hMemDC = ::CreateCompatibleDC(hDC); // Create a compatible bitmap HBITMAP hBitmap = CreateCompatibleBitmap(hDC, nScreenWidth,nScreenHeight); // Select the bitmap into the memory context ::SelectObject(hMemDC,hBitmap); // Do what ever drawing you want into the Device Context ... ... SaveBitmap(hMemDC, hBitmap,"Sample.bmp");
Points of Interest
SetStretchBltMode(hDC,HALFTONE)
Try out this function, this improves the quality of StretchBlt(). I think with our using this mode, SretchBlt() function cannot give you the required quality if you are dealing with big bitmaps.