C++ screen shot - c++

Question

How do I capture screen shot using C++? I'm going to be working with Win32.
Please, no MFC code.

Answer 1

#include "windows.h" // should be less than and greater than instead of \"
int CaptureBMP(LPCTSTR szFile)
{
// Source[1]
HDC hdcScr, hdcMem;
HBITMAP hbmScr;
BITMAP bmp;
int iXRes, iYRes;
// Create a normal DC and a memory DC for the entire screen. The
// normal DC provides a "snapshot" of the screen contents. The
// memory DC keeps a copy of this "snapshot" in the associated
// bitmap.
hdcScr = CreateDC("DISPLAY", NULL, NULL, NULL);
hdcMem = CreateCompatibleDC(hdcScr);
iXRes = GetDeviceCaps(hdcScr, HORZRES);
iYRes = GetDeviceCaps(hdcScr, VERTRES);
// Create a compatible bitmap for hdcScreen.
hbmScr = CreateCompatibleBitmap(hdcScr, iXRes, iYRes);
if (hbmScr == 0) return 0;
// Select the bitmaps into the compatible DC.
if (!SelectObject(hdcMem, hbmScr)) return 0;
// Copy color data for the entire display into a
// bitmap that is selected into a compatible DC.
if (!StretchBlt(hdcMem,
0, 0, iXRes, iYRes,
hdcScr,
0, 0, iXRes, iYRes,
SRCCOPY))
return 0;
// Source[2]
PBITMAPINFO pbmi;
WORD cClrBits;
// Retrieve the bitmap's color format, width, and height.
if (!GetObject(hbmScr, sizeof(BITMAP), (LPSTR) &bmp)) return 0;
// Convert the color format to a count of bits.
cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);
if (cClrBits == 1)
cClrBits = 1;
else if (cClrBits <= 4)
cClrBits = 4;
else if (cClrBits <= 8)
cClrBits = 8;
else if (cClrBits <= 16)
cClrBits = 16;
else if (cClrBits <= 24)
cClrBits = 24;
else cClrBits = 32;
// Allocate memory for the BITMAPINFO structure. (This structure
// contains a BITMAPINFOHEADER structure and an array of RGBQUAD
// data structures.)
if (cClrBits != 24)
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER) +
sizeof(RGBQUAD) * (1 << cClrBits));
// There is no RGBQUAD array for the 24-bit-per-pixel format.
else
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER));
// Initialize the fields in the BITMAPINFO structure.
pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = bmp.bmWidth;
pbmi->bmiHeader.biHeight = bmp.bmHeight;
pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
if (cClrBits < 24)
pbmi->bmiHeader.biClrUsed = (1 << cClrBits);
// If the bitmap is not compressed, set the BI_RGB flag.
pbmi->bmiHeader.biCompression = BI_RGB;
// Compute the number of bytes in the array of color
// indices and store the result in biSizeImage.
pbmi->bmiHeader.biSizeImage = (pbmi->bmiHeader.biWidth + 7) / 8
* pbmi->bmiHeader.biHeight * cClrBits;
// Set biClrImportant to 0, indicating that all of the
// device colors are important.
pbmi->bmiHeader.biClrImportant = 0;
HANDLE hf; // file handle
BITMAPFILEHEADER hdr; // bitmap file-header
PBITMAPINFOHEADER pbih; // bitmap info-header
LPBYTE lpBits; // memory pointer
DWORD dwTotal; // total count of bytes
DWORD cb; // incremental count of bytes
BYTE *hp; // byte pointer
DWORD dwTmp;
pbih = (PBITMAPINFOHEADER) pbmi;
lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);
if (!lpBits) return 0;
// Retrieve the color table (RGBQUAD array) and the bits
// (array of palette indices) from the DIB.
if (!GetDIBits(hdcMem, hbmScr, 0, (WORD) pbih->biHeight, lpBits, pbmi, DIB_RGB_COLORS)) return 0;
// Create the .BMP file.
hf = CreateFile(szFile,
GENERIC_READ | GENERIC_WRITE,
(DWORD) 0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
(HANDLE) NULL);
if (hf == INVALID_HANDLE_VALUE) return 0;
hdr.bfType = 0x4d42; // 0x42 = "B" 0x4d = "M"
// Compute the size of the entire file.
hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed *
sizeof(RGBQUAD) + pbih->biSizeImage);
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;
// Compute the offset to the array of color indices.
hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed *
sizeof (RGBQUAD);
// Copy the BITMAPFILEHEADER into the .BMP file.
if (!WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER), (LPDWORD) &dwTmp, NULL)) return 0;
// Copy the BITMAPINFOHEADER and RGBQUAD array into the file.
if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
+ pbih->biClrUsed * sizeof (RGBQUAD),
(LPDWORD) &dwTmp, NULL))
return 0;
// Copy the array of color indices into the .BMP file.
dwTotal = cb = pbih->biSizeImage;
hp = lpBits;
if (!WriteFile(hf, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp, NULL)) return 0;
// Close the .BMP file.
if (!CloseHandle(hf)) return 0;
// Free memory.
GlobalFree((HGLOBAL)lpBits);
ReleaseDC(0, hdcScr);
ReleaseDC(0, hdcMem);
return 1;
}

Answer 2

There you go, win32 GDI:
http://www.eggheadcafe.com/software/aspnet/32040380/screenshot-of-a-region-to-a-bmp.aspx
Or you could go straight to the MSDN:
http://msdn.microsoft.com/en-us/library/dd183402(v=VS.85).aspx