MFC在MM_ANISOTROPIC映射模式下使用双缓冲

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OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)设置映射模式

pDC->SetMapMode(MM_ANISOTROPIC);

CRect rcClient;

GetClientRect(rcClient);

int cx = rcClient.Width();

int cy = rcClient.Height();

pDC->SetViewportOrg(cx/2, cy/2);

pDC->SetViewportExt(cx, -cy);

pDC->SetWindowExt(1000, 1000);

在OnDraw(CDC* pDC)实现如下

CRect rcClient;

GetClientRect(rcClient);

int cx = rcClient.Width();

int cy = rcClient.Height();

CDC memDc;

// 1.创建内存DC

memDc.CreateCompatibleDC(NULL);

CBitmap memBtm;

// 2.创建内存位图（没有该位图不能再内存中作图，相当于画板）

memBtm.CreateCompatibleBitmap(pDC, cx, cy);

memDc.SelectObject(&memBtm);

// 设置映射模式

memDc.SetMapMode(MM_ANISOTROPIC);

memDc.SetViewportOrg(cx/2, cy/2);

memDc.SetViewportExt(cx, -cy);

memDc.SetWindowExt(1000, 1000);

// 设备坐标转为逻辑坐标(特别重要）

memDc.DPtoLP(rcClient);

memDc.BitBlt(rcClient.left, rcClient.top, rcClient.Width(), rcClient.Height(),

pDC, rcClient.left, rcClient.top, SRCCOPY);

// 填充内存画板颜色，不然为黑色

memDc.FillSolidRect(rcClient.left, rcClient.top, rcClient.Width(), rcClient.Height(),RGB(255,255,255));

CPen pen;

pen.CreatePen(PS_SOLID, 1, RGB(234,23,53));

CPen *pOldPen = (CPen*)memDc.SelectObject(&pen);

memDc.MoveTo(0, 480);

memDc.LineTo(0, -480);

memDc.MoveTo(-480, 0);

memDc.LineTo(480, 0);

memDc.SelectObject(pOldPen);

pen.DeleteObject();

const double PI = 3.141592653589793238462643383279;

const int MultiplyEachUnitOnX = 50;

const int MultiplyEachUnitOnY = 500;

// 绘制正弦波

for(double i = -400; i < 400; i += 0.01)

{

double j = sin(PI / MultiplyEachUnitOnX * i) * MultiplyEachUnitOnY;

memDc.SetPixel(i, j, RGB(0, 0, 255));

}

pDC->BitBlt(rcClient.left, rcClient.top, rcClient.Width(), rcClient.Height(),

&memDc, rcClient.left, rcClient.top, SRCCOPY);

ReleaseDC(&memDc);

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