请问如何在屏幕和纸上精确现实和打印一个150毫米的矩形？

[noho]

我的代码如下
//设置映射模式为0.1毫米
SetMapMode(di.hdcDraw, MM_LOMETRIC);
//红色画刷，蓝色线
HBRUSH hBrush = CreateSolidBrush(RGB(255, 0, 0));
HBRUSH hBrushOld = (HBRUSH)SelectObject(di.hdcDraw, hBrush);
HPEN hPen = CreatePen(PS_SOLID, 0, RGB(0, 255, 0));
HPEN hPenOld = (HPEN)SelectObject(di.hdcDraw, hPen);
//画150毫米的矩形
RECT rc = {0, 0, 1500, -1500};
PatBlt(di.hdcDraw, rc.left, rc.top, rc.right, rc.bottom, PATCOPY);
//画间距为10毫米的16条线
MoveToEx(di.hdcDraw, rc.left, rc.bottom, NULL);
LineTo(di.hdcDraw, rc.right, rc.bottom);
for(int i = 0; i < 16; i++)
{
MoveToEx(di.hdcDraw, 100 * i, rc.top, NULL);
LineTo(di.hdcDraw, 100 * i, rc.bottom);
}
//清除资源
SelectObject(di.hdcDraw, hBrushOld);
SelectObject(di.hdcDraw, hPenOld);
DeleteObject(hBrush);
DeleteObject(hPen);
但是不管是屏幕显示出来的还是打印出来的都和150毫米差一点
请各位大虾不吝赐教
多谢先