如何：取得字型度量資訊

類別 FontFamily 提供下列方法，可擷取特定系列/樣式組合的各種計量：

• GetEmHeight（FontStyle）

• GetCellAscent（FontStyle）

• GetCellDescent（FontStyle）

• GetLineSpacing（FontStyle）

這些方法傳回的值是以字型設計單位表示，因此它們與特定 Font 物件的大小和單位無關。

下圖顯示各種計量：

範例

下列範例會顯示 Arial 字型系列一般樣式的計量。 程式碼也會建立 Font 大小為 16 圖元的物件（以 Arial 系列為基礎），並顯示該特定 Font 物件的度量（以圖元為單位）。

下圖顯示範常式序代碼的輸出：

請注意上圖中的前兩行輸出。 物件 Font 會傳回大小為 16，而 FontFamily 物件會傳回 2,048 的 em 高度。 這兩個數字（16 和 2,048）是轉換字型設計單位與物件單位（在此案例中為圖元） Font 之間轉換的關鍵。

例如，您可以將向量從設計單位轉換成圖元，如下所示：

下列程式碼會設定 物件的資料成員 PointF ， Y 以垂直放置文字。 每個新文字行的 Y 座標都會增加 font.Height 。 物件的 Height 屬性 Font 會傳回該特定 Font 物件的行距（以圖元為單位）。 在此範例中，傳 Height 回的數位是 19。 請注意，這與將行距度量轉換成圖元所取得的數位（四捨五入為整數）相同。

請注意，em 高度（也稱為大小或 em 大小）不是上升和下降的總和。 上升和下降的總和稱為細胞高度。 儲存格高度減去內部前置值等於 em 高度。 儲存格高度加上外部前置線等於行距。

string infoString = "";  // enough space for one line of output
int ascent;             // font family ascent in design units
float ascentPixel;      // ascent converted to pixels
int descent;            // font family descent in design units
float descentPixel;     // descent converted to pixels
int lineSpacing;        // font family line spacing in design units
float lineSpacingPixel; // line spacing converted to pixels

FontFamily fontFamily = new FontFamily("Arial");
Font font = new Font(
   fontFamily,
   16, FontStyle.Regular,
   GraphicsUnit.Pixel);
PointF pointF = new PointF(10, 10);
SolidBrush solidBrush = new SolidBrush(Color.Black);

// Display the font size in pixels.
infoString = "font.Size returns " + font.Size + ".";
e.Graphics.DrawString(infoString, font, solidBrush, pointF);

// Move down one line.
pointF.Y += font.Height;

// Display the font family em height in design units.
infoString = "fontFamily.GetEmHeight() returns " +
   fontFamily.GetEmHeight(FontStyle.Regular) + ".";
e.Graphics.DrawString(infoString, font, solidBrush, pointF);

// Move down two lines.
pointF.Y += 2 * font.Height;

// Display the ascent in design units and pixels.
ascent = fontFamily.GetCellAscent(FontStyle.Regular);

// 14.484375 = 16.0 * 1854 / 2048
ascentPixel =
   font.Size * ascent / fontFamily.GetEmHeight(FontStyle.Regular);
infoString = "The ascent is " + ascent + " design units, " + ascentPixel +
   " pixels.";
e.Graphics.DrawString(infoString, font, solidBrush, pointF);

// Move down one line.
pointF.Y += font.Height;

// Display the descent in design units and pixels.
descent = fontFamily.GetCellDescent(FontStyle.Regular);

// 3.390625 = 16.0 * 434 / 2048
descentPixel =
   font.Size * descent / fontFamily.GetEmHeight(FontStyle.Regular);
infoString = "The descent is " + descent + " design units, " +
   descentPixel + " pixels.";
e.Graphics.DrawString(infoString, font, solidBrush, pointF);

// Move down one line.
pointF.Y += font.Height;

// Display the line spacing in design units and pixels.
lineSpacing = fontFamily.GetLineSpacing(FontStyle.Regular);

// 18.398438 = 16.0 * 2355 / 2048
lineSpacingPixel =
font.Size * lineSpacing / fontFamily.GetEmHeight(FontStyle.Regular);
infoString = "The line spacing is " + lineSpacing + " design units, " +
   lineSpacingPixel + " pixels.";
e.Graphics.DrawString(infoString, font, solidBrush, pointF);

Dim infoString As String = "" ' enough space for one line of output
Dim ascent As Integer ' font family ascent in design units
Dim ascentPixel As Single ' ascent converted to pixels
Dim descent As Integer ' font family descent in design units
Dim descentPixel As Single ' descent converted to pixels
Dim lineSpacing As Integer ' font family line spacing in design units
Dim lineSpacingPixel As Single ' line spacing converted to pixels
Dim fontFamily As New FontFamily("Arial")
Dim font As New Font( _
   fontFamily, _
   16, _
   FontStyle.Regular, _
   GraphicsUnit.Pixel)
Dim pointF As New PointF(10, 10)
Dim solidBrush As New SolidBrush(Color.Black)

' Display the font size in pixels.
infoString = "font.Size returns " & font.Size.ToString() & "."
e.Graphics.DrawString(infoString, font, solidBrush, pointF)

' Move down one line.
pointF.Y += font.Height

' Display the font family em height in design units.
infoString = "fontFamily.GetEmHeight() returns " & _
   fontFamily.GetEmHeight(FontStyle.Regular) & "."
e.Graphics.DrawString(infoString, font, solidBrush, pointF)

' Move down two lines.
pointF.Y += 2 * font.Height

' Display the ascent in design units and pixels.
ascent = fontFamily.GetCellAscent(FontStyle.Regular)

' 14.484375 = 16.0 * 1854 / 2048
ascentPixel = _
   font.Size * ascent / fontFamily.GetEmHeight(FontStyle.Regular)
infoString = "The ascent is " & ascent & " design units, " & ascentPixel _
   & " pixels."
e.Graphics.DrawString(infoString, font, solidBrush, pointF)

' Move down one line.
pointF.Y += font.Height

' Display the descent in design units and pixels.
descent = fontFamily.GetCellDescent(FontStyle.Regular)

' 3.390625 = 16.0 * 434 / 2048
descentPixel = _
   font.Size * descent / fontFamily.GetEmHeight(FontStyle.Regular)
infoString = "The descent is " & descent & " design units, " & _
   descentPixel & " pixels."
e.Graphics.DrawString(infoString, font, solidBrush, pointF)

' Move down one line.
pointF.Y += font.Height

' Display the line spacing in design units and pixels.
lineSpacing = fontFamily.GetLineSpacing(FontStyle.Regular)

' 18.398438 = 16.0 * 2355 / 2048
lineSpacingPixel = _
   font.Size * lineSpacing / fontFamily.GetEmHeight(FontStyle.Regular)
infoString = "The line spacing is " & lineSpacing & " design units, " & _
   lineSpacingPixel & " pixels."
e.Graphics.DrawString(infoString, font, solidBrush, pointF)

編譯程式碼

上述範例設計是為搭配 Windows Form 使用所設計，而且需要 PaintEventArgse，這是 PaintEventHandler 的參數。

另請參閱

• Windows Forms 中的圖形和繪圖
• 使用字型和文字