我使用
FontMetrics.getHeight()
来获取字符串的高度,但它给了我一个错误的值,切断了字符串字符的下降部分。有更好的功能我可以使用吗?
下面的
getStringBounds()
方法基于当前 GlyphVector
字体的 Graphics2D
,对于一行文本字符串非常有效:
public class StringBoundsPanel extends JPanel
{
public StringBoundsPanel()
{
setBackground(Color.white);
setPreferredSize(new Dimension(400, 247));
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// must be called before getStringBounds()
g2.setFont(getDesiredFont());
String str = "My Text";
float x = 140, y = 128;
Rectangle bounds = getStringBounds(g2, str, x, y);
g2.setColor(Color.red);
g2.drawString(str, x, y);
g2.setColor(Color.blue);
g2.draw(bounds);
g2.dispose();
}
private Rectangle getStringBounds(Graphics2D g2, String str,
float x, float y)
{
FontRenderContext frc = g2.getFontRenderContext();
GlyphVector gv = g2.getFont().createGlyphVector(frc, str);
return gv.getPixelBounds(null, x, y);
}
private Font getDesiredFont()
{
return new Font(Font.SANS_SERIF, Font.BOLD, 28);
}
private void startUI()
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(this);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) throws Exception
{
final StringBoundsPanel tb = new StringBoundsPanel();
SwingUtilities.invokeAndWait(new Runnable()
{
public void run()
{
tb.startUI();
}
});
}
}
请注意,为了清楚起见,我省略了导入。
结果:
是什么让您认为它返回了错误的值?您对返回结果的期望与规范不符的可能性要大得多。请注意,如果字体中的某些字形超过或低于这些值,那就完全没问题。
getMaxDescent()
和 getMaxAscent()
应该告诉您字体中任何字形的这些字段的绝对最大值。
如果你想知道特定字符串的指标,那么你肯定想调用
getLineMetrics()
。
FontMetrics.getAscent() 和 FontMetrics.getDescent() 可能可以解决问题。
getHeight()
无法切断字符串的下行部分,只有拉动字符串才能做到这一点。您正在使用从 getHeight
返回的高度以某种方式绘制字符串,并且很可能您误用了高度。例如,如果将字符串的起点定位在 getHeight() 高的框的底部,则文本的基线将位于框的底部边缘,并且下降部分很可能会被剪裁。
文本几何是一个复杂的话题,充满了奇异的历史文物。正如其他人所建议的,使用
getAscent
和 getDescent
尝试将基线正确定位在盒子内。
我最近编写了下面的代码,因为我需要对字体的特定范围进行像素完美的高度测量(例如:所有较低的字符或所有数字)。
如果您需要更快的代码(我的代码有 for 循环),我建议在启动时运行一次以获取数组中的所有值(例如从 1 到 100),然后使用该数组。
该代码基本上将输入字符串中的所有字符绘制在 250x250 位图上重叠的同一位置(如果需要则增加或减少),它开始从顶部查找像素,然后从底部查找像素,然后返回找到的最大高度。即使它是为字符范围设计的,它也适用于普通字符串。这意味着在评估常规字符串时存在某种冗余,因为某些字符重复。因此,如果您的输入字符串超过字母表计数 (26),请使用“tRange”输入:“abcd...z”和其他可能使用的字符。速度更快了。
希望有帮助。
public int getFontPixelHeight(float inSize, Paint sourcePaint, String tRange)
{
// It is assumed that the font is already set in the sourcePaint
int bW = 250, bH = 250; // bitmap's width and height
int firstContact = -1, lastContact = -2; // Used when scanning the pixel rows. Initial values are set so that if no pixels found, the returned result is zero.
int tX = (int)(bW - inSize)/2, tY = (int)(bH - inSize)/2; // Used for a rough centering of the displayed characters
int tSum = 0;
// Preserve the original paint attributes
float oldSize = sourcePaint.getTextSize();
int oldColor = sourcePaint.getColor();
// Set the size/color
sourcePaint.setTextSize(inSize); sourcePaint.setColor(Color.WHITE);
// Create the temporary bitmap/canvas
Bitmap.Config bConf = Bitmap.Config.ARGB_8888;
Bitmap hld = Bitmap.createBitmap(250, 250, bConf);
Canvas canv = new Canvas(hld);
for (int i = 0; i < bH; i++)
{
for (int j = 0; j < bW; j++)
{
hld.setPixel(j, i, 0); // Zero all pixel values. This might seem redundant, but I am not quite sure that creating a blank bitmap means the pixel color value is indeed zero, and I need them to be zero so the addition performed below is correct.
}
}
// Display all characters overlapping at the same position
for (int i = 0; i < tRange.length(); i++)
{
canv.drawText("" + tRange.charAt(i), tX, tY, sourcePaint);
}
for (int i = 0; i < bH; i++)
{
for (int j = 0; j < bW; j++)
{
tSum = tSum + hld.getPixel(j, i);
}
if (tSum > 0) // If we found at least a pixel, save row index and exit loop
{
firstContact = i;
tSum = 0; // Reset
break;
}
}
for (int i = bH - 1; i > 0 ; i--)
{
for (int j = 0; j < bW; j++)
{
tSum = tSum + hld.getPixel(j, i);
}
if (tSum > 0) // If we found at least a pixel, save row index and exit loop
{
lastContact = i;
break;
}
}
// Restore the initial attributes, just in case the paint was passed byRef somehow
sourcePaint.setTextSize(oldSize);
sourcePaint.setColor(oldColor);
return lastContact - firstContact + 1;
}
import javax.swing.*;
import java.awt.*;
public class CustomTextPanel
extends JPanel
{
private StringBuilder text;
private int width, height, x, y;
public CustomTextPanel(String text)
{
setBackground(Color.BLUE);
this.text = new StringBuilder(text);
}
public void setText(String text)
{
this.text = new StringBuilder(text);
}
@Override
public void paintComponent(Graphics g)
{
if (getParent() != null)
{
width = getParent().getWidth() - 40;
height = getParent().getHeight() - 40;
x = 20;
y = 20;
repaint();
}
var g2 = (Graphics2D) g;
g2.setPaint(Color.RED);
// here is rectangle logic
var fontMetrics = g2.getFontMetrics();
g2.drawString(String.valueOf(text), x, y);
g2.setPaint(Color.BLUE);
var outline = new Rectangle(x, y - fontMetrics.getMaxAscent(), width, fontMetrics.getMaxDescent() + fontMetrics.getMaxAscent());
g2.draw(outline);
}
public static void main(String[] args)
{
JFrame frame = new JFrame();
frame.setBounds(0, 0, 600, 400);
frame.getContentPane().add(new CustomTextPanel("abgf"));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}