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


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

    // Retrieve the bitmap color format, width, and height.
    GetObject(hBmp, sizeof(BITMAP), (LPSTR)&bmp);

    // 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.
    // For Windows NT, the width must be DWORD aligned unless
    // the bitmap is RLE compressed. This example shows this.
    // For Windows 95/98/Me, the width must be WORD 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(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
    WORD dwTotal;              // total count of bytes
    WORD cb;                   // incremental count of bytes
    BYTE *hp;                   // byte pointer
    WORD dwTmp;

    pbih = (PBITMAPINFOHEADER) pbi;
    lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);

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

// Create the .BMP file.
    hf = CreateFile(pszFile, GENERIC_READ | GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    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.
    WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER), (LPDWORD) &dwTmp,  NULL);

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

    // Copy the array of color indices into the .BMP file.
    dwTotal = cb = pbih->biSizeImage;
    hp = lpBits;
    WriteFile(hf, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp,NULL);

    // Close the .BMP file.
    CloseHandle(hf);

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


void main(int argc, char *argv[]{
int sx = GetSystemMetrics(SM_CXSCREEN), sy = GetSystemMetrics(SM_CYSCREEN);
HDC hDC = GetDC(GetDesktopWindow());
HDC MyHDC = CreateCompatibleDC(hDC);
HBITMAP hBMP = CreateCompatibleBitmap(hDC, sx, sy);
SelectObject(MyHDC, hBMP);
LOGBRUSH MyBrush;
MyBrush.lbStyle = BS_SOLID;
MyBrush.lbColor = 0xFF0000;
HBRUSH hBrush = CreateBrushIndirect(&MyBrush);
RECT MyRect = {0, 0, sx, sy};
FillRect(MyHDC, &MyRect, hBrush);

BitBlt(MyHDC, 0, 0, sx, sy, hDC, 0, 0, SRCCOPY);
if(argc==2) CreateBMPFile(argv[1], CreateBitmapInfoStruct(hBMP), hBMP, MyHDC);

for(int i=0; i<argc; i++) printf("Argument #%d: %s\n", i, argv[i];
printf("esktop DC = %d\nHBITMAP hBMP = %d", (int)hDC, (int)hBMP);
}

Если человек не способен заметить в коде на любом языке названия API-функций, по которым можно гуглить и мсднить, то человеку никто не поможет.

Как всегда

Шарп много текста но не сюда .Откуда человек спрашівающий такие вещи может знать C++ а ише перевести все ето на свой язык