c# - 确定指定字体的确切字形高度

Question

我已经搜索了很多，尝试了很多，但我找不到合适的解决方案。

我想知道是否有任何方法可以确定指定字体中的精确 字形高度？

我的意思是，当我想确定 DOT 字形的高度时，我应该收到较小的高度，而不是带填充的高度或字体大小。

我找到了确定精确 字形宽度的解决方案 here (我使用了第二种方法)但它不适用于高度。

更新:我需要 .NET 1.1 的解决方案

Answer 1

获取字符指标并不难。 GDI 包含一个函数 GetGlyphOutline您可以使用 GGO_METRICS 常量调用，以获取呈现时包含字形所需的最小 封闭矩形的高度和宽度。即，Arial 字体中点的 10 点字形将给出 1x1 像素的矩形，如果字体大小为 100 点，则字母 I 为 95x.14。

这些是 P/Invoke 调用的声明:

// the declarations
public struct FIXED
{
    public short fract;
    public short value;
}

public struct MAT2
{
    [MarshalAs(UnmanagedType.Struct)] public FIXED eM11;
    [MarshalAs(UnmanagedType.Struct)] public FIXED eM12;
    [MarshalAs(UnmanagedType.Struct)] public FIXED eM21;
    [MarshalAs(UnmanagedType.Struct)] public FIXED eM22;
}

[StructLayout(LayoutKind.Sequential)]
public struct POINT
{
    public int x;
    public int y;
}

[StructLayout(LayoutKind.Sequential)]
public struct POINTFX
{
    [MarshalAs(UnmanagedType.Struct)] public FIXED x;
    [MarshalAs(UnmanagedType.Struct)] public FIXED y;
}

[StructLayout(LayoutKind.Sequential)]
public struct GLYPHMETRICS
{

    public int gmBlackBoxX;
    public int gmBlackBoxY;
    [MarshalAs(UnmanagedType.Struct)] public POINT gmptGlyphOrigin;
    [MarshalAs(UnmanagedType.Struct)] public POINTFX gmptfxGlyphOrigin;
    public short gmCellIncX;
    public short gmCellIncY;

}

private const int GGO_METRICS = 0;
private const uint GDI_ERROR = 0xFFFFFFFF;

[DllImport("gdi32.dll")]
static extern uint GetGlyphOutline(IntPtr hdc, uint uChar, uint uFormat,
   out GLYPHMETRICS lpgm, uint cbBuffer, IntPtr lpvBuffer, ref MAT2 lpmat2);

[DllImport("gdi32.dll", ExactSpelling = true, PreserveSig = true, SetLastError = true)]
static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

如果您不考虑 P/Invoke 冗余，实际代码相当简单。我测试了代码，它有效(您也可以调整以从 GLYPHMETRICS 获取宽度)。

注意:这是临时代码，在现实世界中，您应该使用 ReleaseHandle 和 DeleteObject 清理 HDC 和对象。感谢 user2173353 指出这一点的评论。

// if you want exact metrics, use a high font size and divide the result
// otherwise, the resulting rectangle is rounded to nearest int
private int GetGlyphHeight(char letter, string fontName, float fontPointSize)
{
    // init the font. Probably better to do this outside this function for performance
    Font font = new Font(new FontFamily(fontName), fontPointSize);
    GLYPHMETRICS metrics;

    // identity matrix, required
    MAT2 matrix = new MAT2
        {
            eM11 = {value = 1}, 
            eM12 = {value = 0}, 
            eM21 = {value = 0}, 
            eM22 = {value = 1}
        };

    // HDC needed, we use a bitmap
    using(Bitmap b = new Bitmap(1,1))
    using (Graphics g = Graphics.FromImage(b))
    {
        IntPtr hdc = g.GetHdc();
        IntPtr prev = SelectObject(hdc, font.ToHfont());
        uint retVal =  GetGlyphOutline(
             /* handle to DC   */ hdc, 
             /* the char/glyph */ letter, 
             /* format param   */ GGO_METRICS, 
             /* glyph-metrics  */ out metrics, 
             /* buffer, ignore */ 0, 
             /* buffer, ignore */ IntPtr.Zero, 
             /* trans-matrix   */ ref matrix);

        if(retVal == GDI_ERROR)
        {
            // something went wrong. Raise your own error here, 
            // or just silently ignore
            return 0;
        }


        // return the height of the smallest rectangle containing the glyph
        return metrics.gmBlackBoxY;
    }    
}