int CEnginApp::Draw_Line(int x0, int y0, // starting position int x1, int y1, // ending positionCOLORREF color,    // color indexUNINT *vb_start, int lpitch) // video buffer and memory pitch
{// this function draws a line from xo,yo to x1,y1 using differential error// terms (based on Bresenahams work)
RECT cRect;//GetWindowRect(m_hwnd,&m_x2d_ClientRect);
GetClientRect(m_hwnd, &cRect);ClientToScreen(m_hwnd, (LPPOINT)&cRect);ClientToScreen(m_hwnd, (LPPOINT)&cRect+1);vb_start = vb_start + cRect.left + cRect.top*lpitch;int dx,             // difference in x'sdy,             // difference in y'sdx2,            // dx,dy * 2
        dy2, x_inc,          // amount in pixel space to move during drawingy_inc,          // amount in pixel space to move during drawingerror,          // the discriminant i.e. error i.e. decision variableindex;          // used for looping// pre-compute first pixel address in video buffervb_start = vb_start + x0 + y0*lpitch;// compute horizontal and vertical deltasdx = x1-x0;dy = y1-y0;// test which direction the line is going in i.e. slope angleif (dx>=0){x_inc = 1;} // end if line is moving rightelse{x_inc = -1;dx    = -dx;  // need absolute value
} // end else moving left// test y component of slopeif (dy>=0){y_inc = lpitch;} // end if line is moving downelse{y_inc = -lpitch;dy    = -dy;  // need absolute value
} // end else moving up// compute (dx,dy) * 2dx2 = dx << 1;dy2 = dy << 1;// now based on which delta is greater we can draw the lineif (dx > dy){// initialize error termerror = dy2 - dx; // draw the linefor (index=0; index <= dx; index++){// set the pixel*vb_start = color;// test if error has overflowedif (error >= 0) {error-=dx2;// move to next linevb_start+=y_inc;} // end if error overflowed// adjust the error termerror+=dy2;// move to the next pixelvb_start+=x_inc;} // end for
} // end if |slope| <= 1else{// initialize error termerror = dx2 - dy; // draw the linefor (index=0; index <= dy; index++){// set the pixel*vb_start = color;// test if error overflowedif (error >= 0){error-=dy2;// move to next linevb_start+=x_inc;} // end if error overflowed// adjust the error termerror+=dx2;// move to the next pixelvb_start+=y_inc;} // end for
} // end else |slope| > 1// return successreturn(1);} // end Draw_Line

int CEnginApp::Draw_Line2(int x1,int y1,int x2, int y2,COLORREF color,UNINT *vb_start, int lpitch)
{RECT cRect;//GetWindowRect(m_hwnd,&m_x2d_ClientRect);
GetClientRect(m_hwnd, &cRect);ClientToScreen(m_hwnd, (LPPOINT)&cRect);ClientToScreen(m_hwnd, (LPPOINT)&cRect+1);vb_start = vb_start + cRect.left + cRect.top*lpitch;int dx = x2 - x1;int dy = y2 - y1;int ux = ((dx > 0) << 1) - 1;//x的增量方向，取或-1int uy = ((dy > 0) << 1) - 1;//y的增量方向，取或-1int x = x1, y = y1, eps;//eps为累加误差
eps = 0;dx = abs(dx); dy = abs(dy); if (dx > dy) {for (x = x1; x != x2; x += ux){Plot_Pixel_32(x,y,0,255,0,255,vb_start,lpitch);eps += dy;if ((eps << 1) >= dx){y += uy; eps -= dx;}}}else{for (y = y1; y != y2; y += uy){Plot_Pixel_32(x,y,0,255,0,255,vb_start,lpitch);eps += dx;if ((eps << 1) >= dy){x += ux; eps -= dy;}}}      return 1;
}

                        DD_INIT_STRUCT(ddsd);if (FAILED(lpSface[PrimarySface]->Lock(NULL,&ddsd,DDLOCK_WAIT | DDLOCK_SURFACEMEMORYPTR,NULL)))return false;int x1,y1,x2,y2;for (int i=0;i<100;i++){srand(time(0));x1=rand()%750;y1=rand()%550;x2=rand()%750;y2=rand()%550;Draw_Line2(x1,y1,x2,y2,RGB(0,255,0),(UNINT *)ddsd.lpSurface,ddsd.lPitch>>2);}if (FAILED(lpSface[PrimarySface]->Unlock(NULL)))return false;