Raw/Direct 访问 BITMAPINFO (HBITMAP) 中的像素数据

Question

我想知道如何从屏幕上获取原始像素信息。到目前为止，我一直在将屏幕捕获到 HBITMAP，填充 BITMAPINFO，然后创建此 BITMAPINFO 变量的指针以直接从内存中读取。我知道文件中的 header 必须是 "removed"，所以我将指针直接推进到位图数据（将 sizeof(MyBMInfo2->bmiHeader) 添加到我的指针偏移量）。我也知道这个位图是inversed/topdown，第一个像素在原始数据的末尾。我需要弄清楚如何从图像中给定的 X 和 Y 中提取 R G 和 B 字节，而这正是我无法做到的。所以我问你先生们，一个灯，一个片段或任何提示，可以帮助我从 gdi32 重新创建 Bitmap.GetPixel(x,y) 的肮脏尝试（太慢了，我需要一个更好的）。

到目前为止我的源代码的片段：

...
HDC hCaptureDC  = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, nScreenWidth, nScreenHeight);
HGDIOBJ hOld = SelectObject(hCaptureDC, hBitmap);
BOOL bOK = BitBlt(hCaptureDC,0,0,nScreenWidth, nScreenHeight, hdc,0,0,SRCCOPY|CAPTUREBLT);
SelectObject(hCaptureDC, hOld); // always select the previously selected object once done 
DeleteDC(hCaptureDC);

BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);

// Get the MyBMInfo structure from the bitmap
if(0 == GetDIBits(hdc, hBitmap, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS)) {
    printf("error\n");
}

BITMAPINFO* MyBMInfo2 = &MyBMInfo;
BYTE* bitmapBits=(BYTE*)MyBMInfo2+sizeof(MyBMInfo2->bmiHeader);
//So... how do I acess X and Y RGB bytes now? xD
...

顺便问一下....还有其他更直接的方法可以在不引发内存保护错误的情况下执行此操作吗？或者......另一种更快的方式？谢谢。

--编辑--

使用 Barmak 的代码，我已经弄清楚如何根据当前光标位置访问 X 和 Y rgb，下面是源代码：

#include <windows.h>

int main()
{
    HWND hwnd = GetDesktopWindow();
    RECT rc;
    GetClientRect(hwnd, &rc);
    int width = rc.right;
    int height = rc.bottom;
    if (width < 1 || height < 1)
    {
        OutputDebugStringA("error\n");
        return 0;
    }

    HDC hdc = GetDC(hwnd);

    HDC hCaptureDC = CreateCompatibleDC(hdc);
    HBITMAP hBitmap = CreateCompatibleBitmap(hdc, width, height);
    HGDIOBJ hOld = SelectObject(hCaptureDC, hBitmap);
    BitBlt(hCaptureDC, 0, 0, width, height, hdc, 0, 0, SRCCOPY | CAPTUREBLT);
    SelectObject(hCaptureDC, hOld);

    BITMAPINFO MyBMInfo = { 0 };
    MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);

    BITMAPINFOHEADER bmpInfoHeader = { sizeof(BITMAPINFOHEADER) };
    bmpInfoHeader.biWidth = width;
    bmpInfoHeader.biHeight = height;
    bmpInfoHeader.biPlanes = 1;
    bmpInfoHeader.biBitCount = 32;

    DWORD size = ((width * bmpInfoHeader.biBitCount + 31) / 32) * 4 * height;
    BYTE *bits = malloc(size);

    if (GetDIBits(hdc, hBitmap, 0, height, bits, (BITMAPINFO*)&bmpInfoHeader, DIB_RGB_COLORS))
    {
        OutputDebugStringA("success\n");
        //you can use bits here

        //access bits from upper-left to lower-right corner
        POINT p;
        GetCursorPos(&p);
        int x = p.x;
        int y = p.y;

        int col = x;
        int row = height - y - 1;
        int index = (row * width + col) * 4;

        BYTE b = bits[index + 0];
        BYTE g = bits[index + 1];
        BYTE r = bits[index + 2];

        printf("r:%i g:%i b:%i \n",r,g,b);


    }
    else
    {
        OutputDebugStringA("error\n");
    }

    free(bits);

    DeleteDC(hCaptureDC);
    DeleteObject(hBitmap);
    ReleaseDC(hwnd, hdc);

    return 0;
}

非常感谢 Shemirani 先生。对于谁对我的回答投了反对票，请考虑撤回它？ :) 和平

Answer 1

GetDibBits 需要缓冲区来接收位。您必须分配缓冲区，然后在不再需要时删除。

#include <windows.h>

int WINAPI wWinMain(HINSTANCE, HINSTANCE, LPTSTR, int)
{
    HWND hwnd = GetDesktopWindow();
    RECT rc;
    GetClientRect(hwnd, &rc);
    int width = rc.right;
    int height = rc.bottom;
    if (width < 1 || height < 1)
    {
        OutputDebugStringA("error\n");
        return 0;
    }

    HDC hdc = GetDC(hwnd);

    HDC hCaptureDC = CreateCompatibleDC(hdc);
    HBITMAP hBitmap = CreateCompatibleBitmap(hdc, width, height);
    HGDIOBJ hOld = SelectObject(hCaptureDC, hBitmap);
    BitBlt(hCaptureDC, 0, 0, width, height, hdc, 0, 0, SRCCOPY | CAPTUREBLT);
    SelectObject(hCaptureDC, hOld);

    BITMAPINFO MyBMInfo = { 0 };
    MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);

    BITMAPINFOHEADER bmpInfoHeader = { sizeof(BITMAPINFOHEADER) };
    bmpInfoHeader.biWidth = width;
    bmpInfoHeader.biHeight = height;
    bmpInfoHeader.biPlanes = 1;
    bmpInfoHeader.biBitCount = 32;

    DWORD size = ((width * bmpInfoHeader.biBitCount + 31) / 32) * 4 * height;
    BYTE *bits = malloc(size);

    if (GetDIBits(hdc, hBitmap, 0, height, bits, (BITMAPINFO*)&bmpInfoHeader, DIB_RGB_COLORS))
    {
        OutputDebugStringA("success\n");
        //you can use bits here

        //access bits from lower-left to upper-right corner
        for (int row = 0; row < height; row++)
        {
            for (int col = 0; col < width; col++)
            {
                //for 32 bit image only:
                int index = (row * width + col) * 4;

                BYTE blue  = bits[index + 0];
                BYTE green = bits[index + 1];
                BYTE red   = bits[index + 2];
            }
        }

        //access bits from upper-left to lower-right corner
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                int col = x;
                int row = height - y - 1;
                int index = (row * width + col) * 4;

                BYTE b = bits[index + 0];
                BYTE g = bits[index + 1];
                BYTE r = bits[index + 2];
            }
        }

    }
    else
    {
        OutputDebugStringA("error\n");
    }

    free(bits);

    DeleteDC(hCaptureDC);
    DeleteObject(hBitmap);
    ReleaseDC(hwnd, hdc);

    return 0;
}

Raw/Direct 访问 BITMAPINFO (HBITMAP) 中的像素数据

Raw/Direct acess on pixels data in a BITMAPINFO (HBITMAP)

c

pointers

memory-leaks

bitmap

gdi