Make a screen shot (Win32)

screenshot-win32.c

#include <windows.h>
#include <stdio.h>

void errhandler(char *msg) {
	printf("%s\n", msg);
}

PBITMAPINFO CreateBitmapInfoStruct(HWND hwnd, HBITMAP hBmp)
{
    BITMAP bmp;
    PBITMAPINFO pbmi;
    WORD    cClrBits;

    // Retrieve the bitmap color format, width, and height.
		int test = GetObject(hBmp, sizeof(BITMAP), (LPSTR)&bmp);
		//printf("%d\n", test);
    if (test == 0)
			errhandler("GetObject 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.
    // The width must be DWORD aligned unless the bitmap is RLE
    // compressed.
    pbmi->bmiHeader.biSizeImage = ((pbmi->bmiHeader.biWidth * cClrBits +31) & ~31) /8
                                  * pbmi->bmiHeader.biHeight;
    // Set biClrImportant to 0, indicating that all of the
    // device colors are important.
     pbmi->bmiHeader.biClrImportant = 0;
     return pbmi;
 }

void CreateBMPFile(HWND hwnd, LPTSTR pszFile, PBITMAPINFO pbi,
                  HBITMAP hBMP, HDC hDC)
 {
     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) pbi;
    lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);

    if (!lpBits)
         errhandler("GlobalAlloc");

    // Retrieve the color table (RGBQUAD array) and the bits
    // (array of palette indices) from the DIB.
    if (!GetDIBits(hDC, hBMP, 0, (WORD) pbih->biHeight, lpBits, pbi,
        DIB_RGB_COLORS))
    {
        errhandler("GetDIBits");
    }

    // Create the .BMP file.
    hf = CreateFile(pszFile,
                   GENERIC_READ | GENERIC_WRITE,
                   (DWORD) 0,
                    NULL,
                   CREATE_ALWAYS,
                   FILE_ATTRIBUTE_NORMAL,
                   (HANDLE) NULL);
    if (hf == INVALID_HANDLE_VALUE)
        errhandler("CreateFile");
    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))
    {
       errhandler("WriteFile");
    }

    // Copy the BITMAPINFOHEADER and RGBQUAD array into the file.
    if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
                  + pbih->biClrUsed * sizeof (RGBQUAD),
                  (LPDWORD) &dwTmp, ( NULL)))
        errhandler("WriteFile");

    // 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))
           errhandler("WriteFile");

    // Close the .BMP file.
     if (!CloseHandle(hf))
           errhandler("CloseHandle");

    // Free memory.
    GlobalFree((HGLOBAL)lpBits);
}


int main(int argc, char *argv[]) {
  if (argc != 2) {
		printf("Usage: %s [filename]\n", argv[0]);
		return 1;
	}

	HDC screen = CreateDC("DISPLAY", 0, 0, 0);
	HDC dest = CreateCompatibleDC(screen);

	RECT rect;
	GetWindowRect(GetDesktopWindow(), &rect);

	HBITMAP bmp = CreateCompatibleBitmap(screen, rect.right, rect.bottom);
	SelectObject(dest, bmp);
	BitBlt(dest, 0, 0, rect.right, rect.bottom, screen, 0, 0, SRCCOPY);

  CreateBMPFile(GetDesktopWindow(), argv[1], CreateBitmapInfoStruct(GetDesktopWindow(), bmp), bmp, dest);

	DeleteDC(screen);

	return 0;
}

What is DISPLAY

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