MFC/GDI CRgn CreateEllipticRgn 少了两个像素？

Question

如果我这样做 CRgn::CreateEllipticRgn(0, 0, 120, 120); 结果会在右侧和底部短两个像素。这是为什么？我想也许是因为一个区域在轮廓内而不是在轮廓上，但在那种情况下，它应该是围绕整个圆圈的 1 个像素边界，而不是在右侧和底部关闭 2 个像素。有什么想法吗？

TIA!!

Answer 1

用图片说明问题：

    //RECT
    hPen = CreatePen(PS_SOLID, 1, RGB(255, 100, 0));
    SelectObject(hdc, hPen);
    Rectangle(hdc, 10, 10, 130, 130);
    //Ellipse
    hBrush = CreateSolidBrush(RGB(255, 0, 0));
    HRGN hTemp = CreateEllipticRgn(10, 10, 130, 130);
    FrameRgn(hdc, hTemp, hBrush, 1, 1);

来自Rectangle function，指出：

The rectangle that is drawn excludes the bottom and right edges.

If a PS_NULL pen is used, the dimensions of the rectangle are 1 pixel less in height and 1 pixel less in width.

来自CreateEllipticRgn，指出：

A bounding rectangle defines the size, shape, and orientation of the region: The long sides of the rectangle define the length of the ellipse's major axis; the short sides define the length of the ellipse's minor axis; and the center of the rectangle defines the intersection of the major and minor axes.

从测试结果来看，椭圆的长宽不包括底边和右边。

MFC/GDI CRgn CreateEllipticRgn 少了两个像素？

MFC/GDI CRgn CreateEllipticRgn is two pixels short?

winapi

mfc

gdi