c# – 确定指定字体中的精确字形高度

获取角色指标并不难. GDI包含一个函数 GetGlyphOutline,您可以使用GGO_METRICS常量调用该函数,以获取在呈现时包含字形所需的最小包围矩形的高度和宽度.即,字体Arial中的点的10点字形将给出一个1×1像素的矩形,对于字母I 95x.14,如果字体的大小为100点.

这些是P / Invoke电话的声明：

// 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);

实际的代码,相当琐碎,如果你不考虑P / Invoke的冗余.我测试了代码,它工作(您可以调整以获得宽度从GLYPHMETRICS).

注意：这是特设代码,在现实世界中,您应该使用ReleaseHandle和DeleteObject清理HDC和对象.感谢user2173353的评论指出了这一点.

// 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,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;
    }    
}