c++ - winapi中保存位图问题

Question

它写入我的 BITMAP.bmp 文件，但当我尝试在 Windows 照片查看器中查看它时，它说“Windows 照片查看器无法打开此图片，因为文件似乎已损坏、损坏或太大。”我知道我可能应该将这些函数放入头文件中，但我从来没有真正深入研究过一个项目来真正制作头文件，所以我忘记了如何做。如果有人知道 Windows 照片查看器中图片的大小限制，我将不胜感激。我从 MSDN 中获得了其中一些功能(毫不羞愧)。错误处理可能会更好，但我没有 errorhandler.h。我不完全确定所有功能是如何工作的，因为正如我所说，我使用了一些来自 MSDN 的代码。我将非常感谢任何可以帮助我的人。 :)

#include <errorrep.h>
#include <windows.h>
#include <iostream>
using namespace std;

namespace Globals{
    HBITMAP hBitmap;
    HDC hScreen;
}
using namespace Globals;

void GetScreenShot(void)
{
    int x1, y1, x2, y2, w, h;
    LPSIZE lpSize;
    LPVOID lpvBits;
    // get screen dimensions
    x1  = GetSystemMetrics(SM_XVIRTUALSCREEN);
    x2  = GetSystemMetrics(SM_CXVIRTUALSCREEN);
    y1  = GetSystemMetrics(SM_YVIRTUALSCREEN);
    y2  = GetSystemMetrics(SM_CYVIRTUALSCREEN);
    w   = x2-x1;
    h   = y2-y1;

    // copy screen to bitmap
    hScreen = GetDC(NULL);
    HDC     hDC     = CreateCompatibleDC(hScreen);
    hBitmap = CreateCompatibleBitmap(hScreen, w, h);
    HGDIOBJ old_obj = SelectObject(hDC, hBitmap);
    BOOL    bRet    = BitBlt(hDC, 0, 0, w, h, hScreen, x1, y1, SRCCOPY);
    GetBitmapDimensionEx(hBitmap, lpSize);
    GetBitmapBits(hBitmap, (LONG)lpSize, lpvBits);
    // save bitmap to clipboard
    OpenClipboard(NULL);
    EmptyClipboard();
    SetClipboardData(CF_BITMAP, hBitmap);
    CloseClipboard();
    // clean up
    SelectObject(hDC, old_obj);
    /*DeleteDC(hDC);
    ReleaseDC(NULL, hScreen);
    DeleteObject(hBitmap);*/
}

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

    // Retrieve the bitmap color format, width, and height.
    if (!GetObject(hBmp, sizeof(BITMAP), (LPSTR)&bmp))
        //errhandler("GetObject", hwnd);
        cout << "Error: CreateBitmapInfoStruct" << endl;

    // 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 these formats: 24-bit-per-pixel or 32-bit-per-pixel

     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", hwnd);
        cout << "!lpBits" << endl;
    // 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", hwnd);
        cout << "Error 1" << endl;
    }

    // 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", hwnd);
    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", hwnd);
       cout << "!WriteFile" << endl;
    }

    // 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", hwnd);
        cout << "!WriteFile" << endl;

    // 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", hwnd);
           cout << "if (!WriteFile(hf, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp,NULL))" << endl;

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

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

int main() {
    cout << "ScreenShot - Takes a screen shot\nScreen shot will be put in your clipboard"
    "\nThere will be 10 seconds before it takes the screen shot\n" << endl;
    string input;
    do
    {
        cin >> input;

        if(input == "ScreenShot")
        {
            /*for(int i=1; i<11; i++)
            {
                Sleep(1000);
                cout << i << endl;
                if(i == 10)
                {
                    break;
                }
            }*/
            GetScreenShot();
            PBITMAPINFO pbmi = CreateBitmapInfoStruct(hBitmap);
            CreateBMPFile("C:\\Users\\Owner\\Desktop\\BITMAP.bmp", pbmi, hBitmap, hScreen);
            cout << "ScreenShot taken!" << endl;
            cin.ignore(2);
            Sleep(3000);
            break;
        }
        else
        {
            cout << "Invalid command." << endl;
        }

    } while(true);

    return 0;
}

Answer 1

将未初始化的值传递给 GetBitmapDimensionEx 和 GetBitmapBits 似乎不太好，所以删除它们，因为它们似乎没有被使用。

void GetScreenShot(void)
{
    int x1, y1, x2, y2, w, h;
    // get screen dimensions
    x1  = GetSystemMetrics(SM_XVIRTUALSCREEN);
    x2  = GetSystemMetrics(SM_CXVIRTUALSCREEN);
    y1  = GetSystemMetrics(SM_YVIRTUALSCREEN);
    y2  = GetSystemMetrics(SM_CYVIRTUALSCREEN);
    w   = x2-x1;
    h   = y2-y1;

    // copy screen to bitmap
    hScreen = GetDC(NULL);
    HDC     hDC     = CreateCompatibleDC(hScreen);
    hBitmap = CreateCompatibleBitmap(hScreen, w, h);
    HGDIOBJ old_obj = SelectObject(hDC, hBitmap);
    BOOL    bRet    = BitBlt(hDC, 0, 0, w, h, hScreen, x1, y1, SRCCOPY);
    // save bitmap to clipboard
    OpenClipboard(NULL);
    EmptyClipboard();
    SetClipboardData(CF_BITMAP, hBitmap);
    CloseClipboard();
    // clean up
    SelectObject(hDC, old_obj);
    /*DeleteDC(hDC);
    ReleaseDC(NULL, hScreen);
    DeleteObject(hBitmap);*/
}

然后，即使 hf != INVALID_HANDLE_VALUE 也设置 hdr.bfType。

改变

    if (hf == INVALID_HANDLE_VALUE)
        //errhandler("CreateFile", hwnd);
    hdr.bfType = 0x4d42;        // 0x42 = "B" 0x4d = "M"

到

    if (hf == INVALID_HANDLE_VALUE)
    {
        //errhandler("CreateFile", hwnd);
    }
    hdr.bfType = 0x4d42;        // 0x42 = "B" 0x4d = "M"

(加括号)

使用 LPCTSTR 而不是 LPTSTR 作为 CreateBMPFile 的参数的 pszFile 类型也很好以避免在传递字符串文字时出现编译器警告。