GraphicsPath类以不同的方式计算文本对象的大小（如评论中已经指出）。文本大小是使用
Ems边界矩形大小计算的。
Em是与目标设备上下文无关的印刷度量单位。它指的是字体最宽字母通常是字母“M”（发音为em）所占据的矩形区域。
目标
Em大小可以通过两种不同的方式计算：一种包括
Font descent，另一种则不包括。
float EMSize = (Font.SizeInPoints * [FontFamily].GetCellAscent([FontStyle])
/ [FontFamily].GetEmHeight([FontStyle])
或者
float EMSize = (Font.SizeInPoints *
([FontFamily].GetCellAscent([FontStyle] +
[FontFamily.GetCellDescent([FontStyle])) /
[FontFamily].GetEmHeight([FontStyle])
请参阅以下文档：
FontFamily.GetEmHeight，
FontFamily.GetCellAscent 和
FontFamily.GetCellDescent
我在此处插入了您可以在文档中找到的图像。
请参考此处包含的一般信息：
使用字体和文本 (MSDN)
该文档报告了如何翻译点、像素和 Ems 的详细信息：
如何：获取字体度量 (MSDN)
我假设您已经有一个包含/引用来自 UI 控件和所需调整的字体设置的类对象。
我在此处添加了一个类，其中包含一些与问题相关的属性的子集。
此类根据用户选择的字体大小执行一些计算。
字体大小通常以点为单位引用。然后使用当前屏幕的 DPI 分辨率将此度量转换为像素 (或从像素维度转换为点)。每个度量也转换为 Ems，如果必须使用 GraphicsPath 绘制文本，则这很方便。
计算 Ems 大小时考虑了字体的 Ascent 和 Descent。
由于混合文本可以具有两个部分，如果没有，则该部分为 = 0，因此 GraphicsPath 类使用此度量更好。
要计算使用特定字体和字体大小绘制的文本的容器框，请使用 GraphicsPath.GetBounds() 方法：
([Canvas] 是提供 Paint 事件的 e.Graphics 对象的控件)
using (var path = new GraphicsPath())
using (var format = new StringFormat(StringFormatFlags.NoClip | StringFormatFlags.NoWrap))
{
format.Alignment = [StringAlignment.Center/Near/Far]; //As selected
format.LineAlignment = [StringAlignment.Center/Near/Far]; //As selected
//Add the Text to the GraphicsPath
path.AddString(fontObject.Text, fontObject.FontFamily,
(int)fontObject.FontStyle, fontObject.SizeInEms,
[Canvas].ClientRectangle, format);
//Ems size (bounding rectangle)
RectangleF textBounds = path.GetBounds(null, fontObject.Outline);
//Location of the Text
fontObject.Location = textBounds.Location;
}
在 [Canvas] 设备上绘制文本：
private void Canvas_Paint(object sender, PaintEventArgs e)
{
using (var path = new GraphicsPath())
using (var format = new StringFormat(StringFormatFlags.NoClip | StringFormatFlags.NoWrap))
{
format.Alignment = [StringAlignment.Center/Near/Far];
format.LineAlignment = [StringAlignment.Center/Near/Far];
path.AddString(fontObject.Text, fontObject.FontFamily, (int)fontObject.FontStyle, fontObject.SizeInEms, Canvas.ClientRectangle, format);
e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
e.Graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
e.Graphics.CompositingMode = CompositingMode.SourceOver;
e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
if (fontObject.Outlined) {
e.Graphics.DrawPath(fontObject.Outline, path);
}
using(var brush = new SolidBrush(fontObject.FillColor)) {
e.Graphics.FillPath(brush, path);
}
}
}
使用此类及相关方法的可视化效果：
作为参考使用的类对象：
public class FontObject
{
private float currentScreenDPI = 0.0F;
private float m_SizeInPoints = 0.0F;
private float m_SizeInPixels = 0.0F;
public FontObject()
: this(string.Empty, FontFamily.GenericSansSerif, FontStyle.Regular, 18F) { }
public FontObject(string text, Font font)
: this(text, font.FontFamily, font.Style, font.SizeInPoints) { }
public FontObject(string text, FontFamily fontFamily, FontStyle fontStyle, float FontSize)
{
if (FontSize < 3) FontSize = 3;
using (Graphics g = Graphics.FromHwndInternal(IntPtr.Zero)) {
currentScreenDPI = g.DpiY;
}
Text = text;
FontFamily = fontFamily;
SizeInPoints = FontSize;
FillColor = Color.Black;
Outline = new Pen(Color.Black, 1);
Outlined = false;
}
public string Text { get; set; }
public FontStyle FontStyle { get; set; }
public FontFamily FontFamily { get; set; }
public Color FillColor { get; set; }
public Pen Outline { get; set; }
public bool Outlined { get; set; }
public float SizeInPoints {
get => m_SizeInPoints;
set { m_SizeInPoints = value;
m_SizeInPixels = (value * 72F) / currentScreenDPI;
SizeInEms = GetEmSize();
}
}
public float SizeInPixels {
get => m_SizeInPixels;
set { m_SizeInPixels = value;
m_SizeInPoints = (value * currentScreenDPI) / 72F;
SizeInEms = GetEmSize();
}
}
public float SizeInEms { get; private set; }
public PointF Location { get; set; }
public RectangleF DrawingBox { get; set; }
private float GetEmSize()
{
return (m_SizeInPoints *
(FontFamily.GetCellAscent(FontStyle) +
FontFamily.GetCellDescent(FontStyle))) /
FontFamily.GetEmHeight(FontStyle);
}
}
字体系列下拉框
创建一个自定义的ComboBox，并将其DrawMode = OwnerDrawVariable：
string[] fontList = FontFamily.Families.Where(f => f.IsStyleAvailable(FontStyle.Regular)).Select(f => f.Name).ToArray();
cboFontFamily.DrawMode = DrawMode.OwnerDrawVariable;
cboFontFamily.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
cboFontFamily.AutoCompleteSource = AutoCompleteSource.CustomSource;
cboFontFamily.AutoCompleteCustomSource.AddRange(fontList);
cboFontFamily.DisplayMember = "Name";
cboFontFamily.Items.AddRange(fontList);
cboFontFamily.Text = "Arial";
事件处理程序：
private void cboFontFamily_DrawItem(object sender, DrawItemEventArgs e)
{
if ((cboFontFamily.Items.Count == 0) || e.Index < 0) return;
e.DrawBackground();
var flags = TextFormatFlags.Left | TextFormatFlags.VerticalCenter;
using (var family = new FontFamily(cboFontFamily.GetItemText(cboFontFamily.Items[e.Index])))
using (var font = new Font(family, 10F, FontStyle.Regular, GraphicsUnit.Point)) {
TextRenderer.DrawText(e.Graphics, family.Name, font, e.Bounds, cboFontFamily.ForeColor, flags);
}
e.DrawFocusRectangle();
}
private void cboFontFamily_MeasureItem(object sender, MeasureItemEventArgs e)
{
e.ItemHeight = (int)this.Font.Height + 4;
}
private void cboFontFamily_SelectionChangeCommitted(object sender, EventArgs e)
{
fontObject.FontFamily = new FontFamily(cboFontFamily.GetItemText(cboFontFamily.SelectedItem));
Canvas.Invalidate();
}
