我正在开发一个项目，该项目可以生成包含相当复杂的数学和科学公式的 PDF。文本以 Times New Roman 呈现，它具有很好的 Unicode 覆盖率，但并不完整。我们有一个系统可以为在 TNR 中没有字形的代码点（如大多数“陌生”数学符号）交换更 Unicode 完整的字体，但我似乎找不到查询的方法*.ttf 文件以查看是否存在给定的字形。到目前为止，我只是硬编码了一个存在哪些代码点的查找表，但我更喜欢自动解决方案。
我在 ASP.net 下的 Web 系统中使用 VB.Net，但任何编程语言/环境中的解决方案都将不胜感激。
编辑：win32 解决方案看起来很棒，但我要解决的具体情况是在 ASP.Net Web 系统中。有没有办法在我的网站中不包含 Windows API DLL 的情况下做到这一点？
这是一个使用 c# 和 windows API 的通行证。
[DllImport("gdi32.dll")]
public static extern uint GetFontUnicodeRanges(IntPtr hdc, IntPtr lpgs);
[DllImport("gdi32.dll")]
public extern static IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
public struct FontRange
{
public UInt16 Low;
public UInt16 High;
}
public List<FontRange> GetUnicodeRangesForFont(Font font)
{
Graphics g = Graphics.FromHwnd(IntPtr.Zero);
IntPtr hdc = g.GetHdc();
IntPtr hFont = font.ToHfont();
IntPtr old = SelectObject(hdc, hFont);
uint size = GetFontUnicodeRanges(hdc, IntPtr.Zero);
IntPtr glyphSet = Marshal.AllocHGlobal((int)size);
GetFontUnicodeRanges(hdc, glyphSet);
List<FontRange> fontRanges = new List<FontRange>();
int count = Marshal.ReadInt32(glyphSet, 12);
for (int i = 0; i < count; i++)
{
FontRange range = new FontRange();
range.Low = (UInt16)Marshal.ReadInt16(glyphSet, 16 + i * 4);
range.High = (UInt16)(range.Low + Marshal.ReadInt16(glyphSet, 18 + i * 4) - 1);
fontRanges.Add(range);
}
SelectObject(hdc, old);
Marshal.FreeHGlobal(glyphSet);
g.ReleaseHdc(hdc);
g.Dispose();
return fontRanges;
}
public bool CheckIfCharInFont(char character, Font font)
{
UInt16 intval = Convert.ToUInt16(character);
List<FontRange> ranges = GetUnicodeRangesForFont(font);
bool isCharacterPresent = false;
foreach (FontRange range in ranges)
{
if (intval >= range.Low && intval <= range.High)
{
isCharacterPresent = true;
break;
}
}
return isCharacterPresent;
}
然后，给定一个要检查的 char toCheck 和一个 Font theFont 来测试它...
if (!CheckIfCharInFont(toCheck, theFont) {
// not present
}
使用 VB.Net 的相同代码
<DllImport("gdi32.dll")> _
Public Shared Function GetFontUnicodeRanges(ByVal hds As IntPtr, ByVal lpgs As IntPtr) As UInteger
End Function
<DllImport("gdi32.dll")> _
Public Shared Function SelectObject(ByVal hDc As IntPtr, ByVal hObject As IntPtr) As IntPtr
End Function
Public Structure FontRange
Public Low As UInt16
Public High As UInt16
End Structure
Public Function GetUnicodeRangesForFont(ByVal font As Font) As List(Of FontRange)
Dim g As Graphics
Dim hdc, hFont, old, glyphSet As IntPtr
Dim size As UInteger
Dim fontRanges As List(Of FontRange)
Dim count As Integer
g = Graphics.FromHwnd(IntPtr.Zero)
hdc = g.GetHdc()
hFont = font.ToHfont()
old = SelectObject(hdc, hFont)
size = GetFontUnicodeRanges(hdc, IntPtr.Zero)
glyphSet = Marshal.AllocHGlobal(CInt(size))
GetFontUnicodeRanges(hdc, glyphSet)
fontRanges = New List(Of FontRange)
count = Marshal.ReadInt32(glyphSet, 12)
For i = 0 To count - 1
Dim range As FontRange = New FontRange
range.Low = Marshal.ReadInt16(glyphSet, 16 + (i * 4))
range.High = range.Low + Marshal.ReadInt16(glyphSet, 18 + (i * 4)) - 1
fontRanges.Add(range)
Next
SelectObject(hdc, old)
Marshal.FreeHGlobal(glyphSet)
g.ReleaseHdc(hdc)
g.Dispose()
Return fontRanges
End Function
Public Function CheckIfCharInFont(ByVal character As Char, ByVal font As Font) As Boolean
Dim intval As UInt16 = Convert.ToUInt16(character)
Dim ranges As List(Of FontRange) = GetUnicodeRangesForFont(font)
Dim isCharacterPresent As Boolean = False
For Each range In ranges
If intval >= range.Low And intval <= range.High Then
isCharacterPresent = True
Exit For
End If
Next range
Return isCharacterPresent
End Function
斯科特的回答很好。如果只检查每个字体的几个字符串（在我们的例子中每个字体一个字符串），这是另一种可能更快的方法。但如果您使用一种字体检查大量文本，可能会更慢。
[DllImport("gdi32.dll", EntryPoint = "CreateDC", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CreateDC(string lpszDriver, string lpszDeviceName, string lpszOutput, IntPtr devMode);
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
private static extern bool DeleteDC(IntPtr hdc);
[DllImport("Gdi32.dll")]
private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);
[DllImport("Gdi32.dll", CharSet = CharSet.Unicode)]
private static extern int GetGlyphIndices(IntPtr hdc, [MarshalAs(UnmanagedType.LPWStr)] string lpstr, int c,
Int16[] pgi, int fl);
/// <summary>
/// Returns true if the passed in string can be displayed using the passed in fontname. It checks the font to
/// see if it has glyphs for all the chars in the string.
/// </summary>
/// <param name="fontName">The name of the font to check.</param>
/// <param name="text">The text to check for glyphs of.</param>
/// <returns></returns>
public static bool CanDisplayString(string fontName, string text)
{
try
{
IntPtr hdc = CreateDC("DISPLAY", null, null, IntPtr.Zero);
if (hdc != IntPtr.Zero)
{
using (Font font = new Font(new FontFamily(fontName), 12, FontStyle.Regular, GraphicsUnit.Point))
{
SelectObject(hdc, font.ToHfont());
int count = text.Length;
Int16[] rtcode = new Int16[count];
GetGlyphIndices(hdc, text, count, rtcode, 0xffff);
DeleteDC(hdc);
foreach (Int16 code in rtcode)
if (code == 0)
return false;
}
}
}
catch (Exception)
{
// nada - return true
Trap.trap();
}
return true;
}
FreeType是一个可以读取 TrueType 字体文件（以及其他）的库，可用于查询特定字形的字体。但是，FreeType 是为渲染而设计的，因此使用它可能会导致您引入比此解决方案所需的更多代码。
不幸的是，即使在 OpenType / TrueType 字体的世界中也没有真正明确的解决方案。字符到字形的映射有十几种不同的定义，具体取决于字体类型和最初设计的平台。您可能会尝试查看Microsoft 的OpenType 规范副本中的cmap 表定义，但这并不容易阅读。
Scott Nichols 发布的代码非常棒，除了一个错误：如果字形 id 大于 Int16.MaxValue，则会引发 OverflowException。为了修复它，我添加了以下功能：
Protected Function Unsign(ByVal Input As Int16) As UInt16
If Input > -1 Then
Return CType(Input, UInt16)
Else
Return UInt16.MaxValue - (Not Input)
End If
End Function
然后将函数 GetUnicodeRangesForFont 中的主 for 循环更改为如下所示：
For i As Integer = 0 To count - 1
Dim range As FontRange = New FontRange
range.Low = Unsign(Marshal.ReadInt16(glyphSet, 16 + (i * 4)))
range.High = range.Low + Unsign(Marshal.ReadInt16(glyphSet, 18 + (i * 4)) - 1)
fontRanges.Add(range)
Next
这篇 Microsoft 知识库文章可能会有所帮助：http: //support.microsoft.com/kb/241020
它有点过时（最初是为 Windows 95 编写的），但一般原则可能仍然适用。示例代码是 C++，但由于它只是调用标准的 Windows API，因此它很可能也可以在 .NET 语言中工作，而且需要一点麻烦。
-Edit- 似乎旧的 95 时代 API 已被微软称为“ Uniscribe ”的新 API 淘汰，它应该能够做你需要做的事情。
我只用了一个 VB.Net 单元测试，没有 WIN32 API 调用。它包括检查特定字符 U+2026（省略号）和 U+2409（HTab）的代码，还返回具有字形的字符数（以及低值和高值）。我只对等宽字体感兴趣，但很容易改变......
Dim fnt As System.Drawing.Font, size_M As Drawing.Size, size_i As Drawing.Size, size_HTab As Drawing.Size, isMonospace As Boolean
Dim ifc = New Drawing.Text.InstalledFontCollection
Dim bm As Drawing.Bitmap = New Drawing.Bitmap(640, 64), gr = Drawing.Graphics.FromImage(bm)
Dim tf As Windows.Media.Typeface, gtf As Windows.Media.GlyphTypeface = Nothing, ok As Boolean, gtfName = ""
For Each item In ifc.Families
'TestContext_WriteTimedLine($"N={item.Name}.")
fnt = New Drawing.Font(item.Name, 24.0)
Assert.IsNotNull(fnt)
tf = New Windows.Media.Typeface(item.Name)
Assert.IsNotNull(tf, $"item.Name={item.Name}")
size_M = System.Windows.Forms.TextRenderer.MeasureText("M", fnt)
size_i = System.Windows.Forms.TextRenderer.MeasureText("i", fnt)
size_HTab = System.Windows.Forms.TextRenderer.MeasureText(ChrW(&H2409), fnt)
isMonospace = size_M.Width = size_i.Width
Assert.AreEqual(size_M.Height, size_i.Height, $"fnt={fnt.Name}")
If isMonospace Then
gtfName = "-"
ok = tf.TryGetGlyphTypeface(gtf)
If ok Then
Assert.AreEqual(True, ok, $"item.Name={item.Name}")
Assert.IsNotNull(gtf, $"item.Name={item.Name}")
gtfName = $"{gtf.FamilyNames(Globalization.CultureInfo.CurrentUICulture)}"
Assert.AreEqual(True, gtf.CharacterToGlyphMap().ContainsKey(AscW("M")), $"item.Name={item.Name}")
Assert.AreEqual(True, gtf.CharacterToGlyphMap().ContainsKey(AscW("i")), $"item.Name={item.Name}")
Dim t = 0, nMin = &HFFFF, nMax = 0
For n = 0 To &HFFFF
If gtf.CharacterToGlyphMap().ContainsKey(n) Then
If n < nMin Then nMin = n
If n > nMax Then nMax = n
t += 1
End If
Next
gtfName &= $",[x{nMin:X}-x{nMax:X}]#{t}"
ok = gtf.CharacterToGlyphMap().ContainsKey(AscW(ChrW(&H2409)))
If ok Then
gtfName &= ",U+2409"
End If
ok = gtf.CharacterToGlyphMap().ContainsKey(AscW(ChrW(&H2026)))
If ok Then
gtfName &= ",U+2026"
End If
End If
Debug.WriteLine($"{IIf(isMonospace, "*M*", "")} N={fnt.Name}, gtf={gtfName}.")
gr.Clear(Drawing.Color.White)
gr.DrawString($"Mi{ChrW(&H2409)} {fnt.Name}", fnt, New Drawing.SolidBrush(Drawing.Color.Black), 10, 10)
bm.Save($"{fnt.Name}_MiHT.bmp")
End If
Next
输出是
M N=Consolas，gtf=Consolas，[x0-xFFFC]#2488，U+2026。
M N=Courier New, gtf=Courier New,[x20-xFFFC]#3177,U+2026。
M N=Lucida 控制台，gtf=Lucida 控制台，[x20-xFB02]#644，U+2026。
M N=Lucida Sans 打字机，gtf=Lucida Sans 打字机，[x20-xF002]#240,U+2026。
M N=MingLiU-ExtB，gtf=MingLiU-ExtB，[x0-x2122]#212。
M N=MingLiU_HKSCS-ExtB，gtf=MingLiU_HKSCS-ExtB，[x0-x2122]#212。
M N=MS 哥特式，gtf=MS 哥特式，[x0-xFFEE]#15760,U+2026。
M N=NSimSun，gtf=NSimSun，[x20-xFFE5]#28737，U+2026。
M N=OCR A 扩展，gtf=OCR A 扩展，[x20-xF003]#248，U+2026。
M N=SimSun，gtf=SimSun，[x20-xFFE5]#28737，U+2026。
M N=SimSun-ExtB，gtf=SimSun-ExtB，[x20-x7F]#96。
M N=Webdings，gtf=Webdings，[x20-xF0FF]#446。