确定指定字体的确切字形高度

Question

我经常搜索并尝试了很多,但我找不到合适的解决方案.

我想知道有没有办法确定指定字体的确切字形高度？

我的意思是在这里,当我想确定DOT字形的高度时,我应该获得较小的高度,但不能使用填充或字体大小来获得高度.

我已经找到了确定的解决方案准确字形宽度在这里(我用第二种方法),但它并不适用于高度工作.

更新:我需要.NET 1.1的解决方案

Answer 1

这不是说很难得到字符规格.GDI包含一个函数GetGlyphOutline,您可以使用GGO_METRICS常量调用该函数来获取渲染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1x1像素的矩形,如果字体是100磅,则为字母I 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,那么实际代码相当简单.我测试了代码,它可以工作(你可以调整以获得宽度GLYPHMETRICS).

注意:这是ad-hoc代码,在现实世界中,你应该用ReleaseHandle和清理HDC和对象DeleteObject.感谢user2173353的评论指出这一点.

// 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, 
             /* 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;
    }    
}