使用 GraphicsPath 正确绘制文本

Question

如下图所示，PictureBox 中的文字与TextBox 中的文字不同。如果我使用 Graphics.DrawString() 它工作正常，但是当我使用图形路径时，它会截断并且不显示整个文本。您认为我的代码有什么问题？

这是我的代码：

public LayerClass DrawString(LayerClass.Type _text, string text, RectangleF rect, Font _fontStyle, PaintEventArgs e)
{
    using (StringFormat string_format = new StringFormat())
    {
        rect.Size = e.Graphics.MeasureString(text, _fontStyle);
        rect.Location = new PointF(Shape.center.X - (rect.Width / 2), Shape.center.Y - (rect.Height / 2));
        if(isOutlinedOrSolid)
        {
            using (GraphicsPath path = new GraphicsPath())
            {
                path.AddString(text, _fontStyle.FontFamily, (int)_fontStyle.Style, rect.Size.Height, rect, string_format);
                e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
                e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
                e.Graphics.CompositingMode = CompositingMode.SourceOver;
                e.Graphics.DrawPath(new Pen(Color.Red, 1), path);
            }
        }
        else
        {
            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
            e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
            e.Graphics.CompositingMode = CompositingMode.SourceOver;
            e.Graphics.DrawString(text,_fontStyle,Brushes.Red, rect.Location);
        }
    }

    this._Text = text;
    this._TextRect = rect;
    return new LayerClass(_text, this, text, rect);
}

Answer 1

看来您一开始就提供了错误的字体大小测量方法，然后又为画笔添加了额外的粗细。试试这个：

using (GraphicsPath path = new GraphicsPath())
{
    path.AddString(
        text,                         
        _fontStyle.FontFamily,      
        (int)_fontStyle.Style,      
        e.Graphics.DpiY * fontSize / 72f,       // em size
        new Point(0, 0),                       // location where to draw text
        string_format);          

    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
    e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
    e.Graphics.CompositingMode = CompositingMode.SourceOver;
    e.Graphics.DrawPath(new Pen(Color.Red), path);
}

Answer 2

GraphicsPath class 以不同的方式计算 Text 对象的大小（如评论中所述）。文本大小是使用 Ems 边界矩形大小计算的。
Em 是独立于目标设备上下文的印刷度量。
它指的是字体最宽的字母所占的矩形，通常是字母“M”（发音为em）。

目的地 Em 大小可以通过两种不同的方式计算：一种包括 Font descent，另一种不包括它。

float EMSize = (Font.SizeInPoints * [FontFamily].GetCellAscent([FontStyle]) 
                                  / [FontFamily].GetEmHeight([FontStyle])

或

float EMSize = (Font.SizeInPoints * 
               ([FontFamily].GetCellAscent([FontStyle] + 
                [FontFamily.GetCellDescent([FontStyle])) / 
                [FontFamily].GetEmHeight([FontStyle])

查看有关以下内容的文档：
FontFamily.GetEmHeight, FontFamily.GetCellAscent and FontFamily.GetCellDescent

我在这里插入您可以在文档中找到的图。

参考此处包含的一般信息：
Using Font and Text (MSDN)

本文档报告了有关如何转换点、像素和 Ems 的细节：
How to: Obtain Font Metrics (MSDN)

我假设您已经有一个 class 对象，其中 contains/references 来自 UI 控件的字体设置和所需的调整。
我在这里添加一个，其中包含一些属性，这些属性包含与问题相关的这些设置的子集。

此 class 根据用户选择的字体大小执行一些计算。
字体大小通常以磅为单位引用。然后使用当前屏幕 DPI 分辨率（或从像素维度转换为点），将此度量转换为像素。每个小节也在 Ems 中转换，如果您必须使用 GraphicsPath 绘制文本，这会派上用场。

Ems 大小是考虑到字体的 Ascent 和 Descent 计算的。
GraphicsPath class 使用此度量效果更好，因为混合文本可以包含两个部分，如果没有，则该部分为 = 0.

要计算以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] 设备上下文上绘制文本：

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]; //As selected
        format.LineAlignment = [StringAlignment.Center/Near/Far]; //As selected

        path.AddString(fontObject.Text, fontObject.FontFamily, (int)fontObject.FontStyle, fontObject.SizeInEms, Canvas.ClientRectangle, format);

        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
        // When text is rendered directly
        e.Graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
        // The composition properties are useful when drawing on a composited surface
        // It has no effect when drawing on a Control's plain surface
        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class及相关方法的视觉效果：

class 对象，用作参考：

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);
    }
}

带有字体系列的组合框
创建自定义 ComboBox 并设置其 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();
}

使用 GraphicsPath 正确绘制文本

Properly draw text using GraphicsPath

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