c++ - C++-SetPixel()太慢

我正在编写类似于Windows中的“绘画”程序。首先，我尝试制作一个“铅笔”函数来处理WM_MOUSEMOVE消息并正确调用SetPixel()。但是，当鼠标移动得太快时，并不会出现所有像素(它们看起来很稀疏)。我想我必须用另一个代码替换该SetPixel()函数，但是我不知道是什么。

最佳答案

在窗口上捕获WM_LBUTTONDOWN和set capture，保存第一个鼠标坐标。

捕获WM_MOUSEMOVE，并从第一个坐标到现在的坐标绘制行。然后，将现在的坐标保存到第一个鼠标坐标中。

重复2。

捕获WM_LBUTTONUP和release capture。

例:

#include <windows.h>
#include <windowsx.h>

LRESULT CALLBACK WndProc(HWND hWnd, UINT iMsg, WPARAM wParam, LPARAM lParam);

int APIENTRY WinMain(HINSTANCE hInst, HINSTANCE, LPSTR, int)
{
    WNDCLASS wc;
    HWND hWnd;
    MSG msg;

    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInst;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = L"adf";
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    RegisterClass(&wc);

    hWnd = CreateWindow(L"adf", NULL, WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, hInst, NULL);
    ShowWindow(hWnd, SW_NORMAL);

    while (GetMessage(&msg, 0, 0, NULL))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
    static int prevx, prevy;

    switch (iMsg)
    {
    case WM_LBUTTONDOWN:
        prevx = GET_X_LPARAM(lParam);
        prevy = GET_Y_LPARAM(lParam);
        SetCapture(hWnd);
        return 0;
    case WM_LBUTTONUP:
        ReleaseCapture();
        return 0;
    case WM_MOUSEMOVE:
        if (GetCapture() == hWnd)
        {
            HDC hdc = GetDC(hWnd);
            MoveToEx(hdc, prevx, prevy, NULL);
            LineTo(hdc, GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
            prevx = GET_X_LPARAM(lParam);
            prevy = GET_Y_LPARAM(lParam);
            ReleaseDC(hWnd, hdc);
        }
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hWnd, iMsg, wParam, lParam);
}