像素数量过后，SetPixel崩溃 [英] SetPixel crashes after an amount of pixels

问题描述

我是MFC/C ++的新手，我正在尝试用像素填充窗口.我发现有一个叫做:

Im new in MFC/C++ an Im trying to fill my windows with pixels.I found out that there is a function which is called :

SetPixel(X，Y，RGB(,,));

SetPixel(X,Y,RGB(,,));

尝试在循环中使用它后，我发现此功能在经过一定像素后会停止，因此它并没有给我我真正想要达到的结果. 这是我的代码:

After I tried to put use it in my loop I found out that this function stops after an amount of pixels.So It don't give me the result I actually want to reach. Here is my code :

void PIXELPROG::OnPaint()
{
    if (IsIconic())
    {
        CPaintDC dc(this);

        SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);


        int cxIcon = GetSystemMetrics(SM_CXICON);
        int cyIcon = GetSystemMetrics(SM_CYICON);
        CRect rect;
        GetClientRect(&rect);
        int x = (rect.Width() - cxIcon + 1) / 2;
        int y = (rect.Height() - cyIcon + 1) / 2;



        dc.DrawIcon(x, y, m_hIcon);
    }
    else
    {
        CDialogEx::OnPaint();
    }


        CStatic * XText = (CStatic *)GetDlgItem(IDC_X);
        CStatic * YText = (CStatic *)GetDlgItem(IDC_YWERT);

        CString XYWert;

    for (int x=0,y=0;;)
    {
        GetDC()->SetPixelV(x, y, RGB(y,x,y));
        XYWert.Format(L"%d",y);

        XText->SetWindowTextW(XYWert);

        ++x;
        if (x == 500)
        {
            ++y;
            x = 0;
        }
        if (y == 100)
        {
            break;
        }
    }
}

我也没有收到任何错误，它只是停止了. 我也用

I also don't get any errors.It is just stopping. I also tried it with

SetPixelV()

SetPixelV()

但两者都没有帮助. 有人知道吗?

But didn't helped neither. Someone got an idea ?

推荐答案

来自

除非设备上下文属于窗口类，否则必须调用ReleaseDC成员函数以在绘制后释放上下文.

Unless the device context belongs to a window class, the ReleaseDC member function must be called to release the context after painting.

由于您没有将GetDC的返回值分配给任何东西，因此您无法调用ReleaseDC.由于尚未发布，因此它们会累积-您的应用程序可以使用的GDI对象总数受到限制，请参见

Since you're not assigning the return value from GetDC to anything, there's no way for you to call ReleaseDC. Since they're not released, they build up - there's a limit to the total number of GDI objects your application can use, see GDI Objects. Once you hit that limit, things go bad very fast (Don't ask me how I know).

如果这是对WM_PAINT消息的响应，则不应首先调用GetDC.您应该使用创建的CPaintDC对象.通常，不要在自己的OnPaint处理程序中调用父OnPaint方法，因为您只能生成一个CPaintDC.

If this is in response to a WM_PAINT message, you shouldn't be calling GetDC in the first place. You should be using the CPaintDC object that you create. As a general rule, don't call the parent OnPaint method in your own OnPaint handler, because you can only generate a single CPaintDC.

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