GetPixel 太慢了

Question

我有一堆方格，每个方格都有我需要识别的特定身份/符号。到目前为止，我有类似的东西：

#include <iostream>
#include <windows.h>

using namespace std;

int main() {
    HDC dc = GetDC(0);
    COLORREF color;
    int sum, x, y;

    while (true) {
        sum = 0;
        Sleep(100);
        for (x = 512; x < 521; x++) {
            for (y = 550; y < 565; y++) {
                color = GetPixel(dc, x, y);
                sum = GetRValue(color) + GetBValue(color) + GetGValue(color);
            }
        }
        cout << "SUM: " << sum << endl;
    }

    return 0;
}

显然到目前为止它只扫描了一个块。问题在于，即使它只有 100 多像素，它也需要非常长的时间。我什至无法想象会发生什么。每次重复需要一秒多，也许两秒。我能做些什么？必须有一种更快的方法来做到这一点。如果我不能查询单个像素，是否有办法获取屏幕区域？该区域不在我的程序窗口内。

Answer 1

Jonathan cmets 在问题中使用 DIB，但没有显示如何使用的答案。为了完整起见，这里是Mister B's code：

COLORREF getcolor(POINT pt) {
    HDC hDc = GetDC(0);
    HDC hDcmem = CreateCompatibleDC(0);
    HBITMAP hBmp = CreateCompatibleBitmap(hDc, 1, 1);
    SelectObject(hDcmem, hBmp);
    BitBlt(hDcmem, 0, 0, 1, 1, hDc, pt.x, pt.y, SRCCOPY);
    LPBITMAPINFO lpbmi = new BITMAPINFO;
    lpbmi->bmiHeader.biBitCount = 24;
    lpbmi->bmiHeader.biCompression = BI_RGB;
    lpbmi->bmiHeader.biPlanes = 1;
    lpbmi->bmiHeader.biHeight = 1;
    lpbmi->bmiHeader.biWidth = 1;
    lpbmi->bmiHeader.biSize = sizeof(BITMAPINFO);
    BYTE lpvBits[4];
    GetDIBits(hDcmem, hBmp, 0, 1, lpvBits, lpbmi, DIB_RGB_COLORS);
    COLORREF currColor = RGB(lpvBits[2], lpvBits[1], lpvBits[0]);
    delete lpbmi;
    DeleteObject(hBmp);
    DeleteDC(hDcmem);
    ReleaseDC(0, hDc);
    return currColor;
}

正如 Ben 在评论中指出的那样，这仍然非常慢，解决方案是使用这些构建块一次复制整个区域。你的代码会变成这样：

#include <iostream>
#include <vector>
#include <windows.h>

int main() {
    int const startX = 512;
    int const endX = 521;
    int const startX = 550;
    int const endY = 565;
    int const width = endX - startX;
    int const height = endY - startY;

    HDC const hDc = GetDC(0);
    HDC const hDcmem = CreateCompatibleDC(0);
    HBITMAP const hBmp = CreateCompatibleBitmap(hDc, width, height);
    auto const oldBmp = SelectObject(hDcmem, hBmp);

    BITMAPINFO bmi{};
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = BI_RGB;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biHeight = height;
    bmi.bmiHeader.biWidth = width;
    bmi.bmiHeader.biSize = sizeof(BITMAPINFO);

    std::vector<RGBQUAD> pixels(height * width);

    while (true) {
        Sleep(100);

        BitBlt(hDcmem, 0, 0, width, height, hDc, startX, startY, SRCCOPY);
        GetDIBits(hDcmem, hBmp, 0, height, &pixels[0], &bmi, DIB_RGB_COLORS);
        int sum = 0;
        for (int i = 0; i < height * width; ++i) {
            sum = pixels[i].R + pixels[i].G + pixels[i].B;
        }

        std::cout << "SUM: " << sum << std::endl;
    }

    SelectObject(hDcmem, oldBmp);
    DeleteObject(hBmp);
    DeleteDC(hDcmem);
    ReleaseDC(0, hDc);

    return 0;
}