// 这也是一种常用的方法 先在内存中创建一个BITMAP 但是不显示 他只用来重画 即满足你的LineTo 然后用 BitBlt
The BitBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context.
BOOL BitBlt(
HDC hdcDest, // handle to destination device context
int nXDest, // x-coordinate of destination rectangle's upper-left
// corner
int nYDest, // y-coordinate of destination rectangle's upper-left
// corner
int nWidth, // width of destination rectangle
int nHeight, // height of destination rectangle
HDC hdcSrc, // handle to source device context
int nXSrc, // x-coordinate of source rectangle's upper-left
// corner
int nYSrc, // y-coordinate of source rectangle's upper-left
// corner
DWORD dwRop // raster operation code
);