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如何：取得字型度量資訊

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FontFamily 類別提供下列方法來擷取特定家族/樣式組合的各種計量：

這些方法傳回的值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：

字型計量的圖例：上方位移、下方位移和前置。

範例

下列範例顯示 Arial 字型家族一般樣式的計量。 此程式碼也會建立大小為 16 像素的 Font 物件 (以 Arial 家族為基礎)，並顯示該特定 Font 物件的計量 (以像素為單位)。

下圖顯示範例程式碼的輸出：

Arial 字型計量的範例程式碼輸出。

請注意上圖中的前兩行輸出。 Font 物件會傳回大小 16，而 FontFamily 物件會傳回 em 高度 2,048。 這兩個數字 (16 和 2,048) 是在字型設計單位與 Font 物件的單位 (在此案例中為像素) 之間進行轉換的關鍵。

例如，您可以將上方位移從設計單位轉換成像素，如下所示：

顯示從設計單位轉換成像素的公式

下列程式碼會設定 Y 物件的 PointF 資料成員，以垂直放置文字。 每新增一行文字，Y 座標都會增加 font.Height。 Height 物件的 Font 屬性會傳回該特定 Font 物件的前置 (以像素為單位)。 在此範例中，Height 傳回的數字是 19。 請注意，這與將行距計量轉換成像素所取得的數字 (四捨五入至整數) 相同。

請注意，em 高度 (也稱為大小或 em 大小) 不是上方位移和下方位移的總和。 上方位移和下方位移的總和稱為字元格高度。 字元格高度減去內部行距等於 em 高度。 字元格高度加上外部行距等於前置。

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

上述範例的設計目的是要與 Windows Forms 搭配使用，而且需要 PaintEventArgse，這是 PaintEventHandler 的參數。

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