java - SVG蝾螈例子？

Question

我在玩 Java 和 SVG Salamander，但不知道如何将简单的 SVG 文件渲染成JPanel.

有人可以给我一个简单的例子吗？尝试按照官方网站中的宽松教程进行操作，但找不到简单的代码来更好地理解。

Answer 1

首先，您需要以某种方式创建图表（com.kitfox.svg.SVGDiagram）。

File f = new File(mysvgfile);
SVGUniverse svgUniverse = new SVGUniverse();
SVGDiagram diagram = svgUniverse.getDiagram(svgUniverse.loadSVG(f.toURL()));

现在，当您想要渲染您的文件时 - 通常来自面板的 paintComponent() 方法 - 您只需要做（g作为 Graphics2D 实例）：

diagram.render(g);

而且（像往常一样？），如果你想以某种修改的方式绘制它：

AffineTransform oldTransform = g.getTransform();
g.scale(...);
g.translate(...);
...
diagram.render(g);
g.setTransform(oldTransform);

Answer 2

存储库有示例代码。如果您想使用最新的，则涉及几个步骤：

1. 安装Apache Maven。

2. 在某处克隆存储库：

   mkdir -p $HOME/dev/java/
   cd $HOME/dev/java
   git clone https://github.com/blackears/svgSalamander
   

3. 更新pom.xml：

   cd svgSalamander/svg-core
   vi pom.xml
   

4. 更改source、target和 JDK 版本号：

   <maven.compiler.source>1.7</maven.compiler.source>
   <maven.compiler.target>1.7</maven.compiler.target>
   
   <jdkVersion>1.7</jdkVersion>
   

5. 保存pom.xml。

6. 使用 Maven 生成 JAR 文件：mvn package

7. 复制target/svgSalamander-1.1.2.jar（确保更改版本号是必要的）到程序的库目录（例如，libs）。

如果您的程序使用Gradle进行构建，请更新依赖项以使用本地 JAR 文件：

dependencies {
  // SVG
  implementation fileTree(include: ['**/*.jar'], dir: 'libs')
}

如果您使用不同的构建系统，则必须相应地更改依赖项。从那里，这是一个使用 SVG Salamander 缩放和光栅化矢量图形资源文件的类：

import com.kitfox.svg.SVGDiagram;
import com.kitfox.svg.SVGException;
import com.kitfox.svg.SVGUniverse;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.net.URL;
import java.util.Map;

import static java.awt.RenderingHints.*;
import static java.awt.image.BufferedImage.TYPE_INT_ARGB;

/**
 * Responsible for converting SVG images into rasterized PNG images.
 */
public class SvgRasterizer {
  public final static Map<Object, Object> RENDERING_HINTS = Map.of(
      KEY_ANTIALIASING,
      VALUE_ANTIALIAS_ON,
      KEY_ALPHA_INTERPOLATION,
      VALUE_ALPHA_INTERPOLATION_QUALITY,
      KEY_COLOR_RENDERING,
      VALUE_COLOR_RENDER_QUALITY,
      KEY_DITHERING,
      VALUE_DITHER_DISABLE,
      KEY_FRACTIONALMETRICS,
      VALUE_FRACTIONALMETRICS_ON,
      KEY_INTERPOLATION,
      VALUE_INTERPOLATION_BICUBIC,
      KEY_RENDERING,
      VALUE_RENDER_QUALITY,
      KEY_STROKE_CONTROL,
      VALUE_STROKE_PURE,
      KEY_TEXT_ANTIALIASING,
      VALUE_TEXT_ANTIALIAS_ON
  );

  private final static SVGUniverse sRenderer = new SVGUniverse();

  /**
   * Rasterizes a vector graphic to a given size using a {@link BufferedImage}.
   * The rendering hints are set to produce high quality output.
   *
   * @param path   Fully qualified path to the image resource to rasterize.
   * @param dstDim The output image dimensions.
   * @return The rasterized {@link Image}.
   * @throws SVGException Could not open, read, parse, or render SVG data.
   */
  public Image rasterize( final String path, final Dimension dstDim )
      throws SVGException {
    final var diagram = loadDiagram( path );
    final var wDiagram = diagram.getWidth();
    final var hDiagram = diagram.getHeight();
    final var srcDim = new Dimension( (int) wDiagram, (int) hDiagram );

    final var scaled = fit( srcDim, dstDim );
    final var wScaled = (int) scaled.getWidth();
    final var hScaled = (int) scaled.getHeight();

    final var image = new BufferedImage( wScaled, hScaled, TYPE_INT_ARGB );

    final var g = image.createGraphics();
    g.setRenderingHints( RENDERING_HINTS );

    final var transform = g.getTransform();
    transform.setToScale( wScaled / wDiagram, hScaled / hDiagram );

    g.setTransform( transform );
    diagram.render( g );
    g.dispose();

    return image;
  }

  /**
   * Gets an instance of {@link URL} that references a file in the
   * application's resources.
   *
   * @param path The full path (starting at the root), relative to the
   *             application or JAR file's resources directory.
   * @return A {@link URL} to the file or {@code null} if the path does not
   * point to a resource.
   */
  private URL getResourceUrl( final String path ) {
    return SvgRasterizer.class.getResource( path );
  }

  /**
   * Loads the resource specified by the given path into an instance of
   * {@link SVGDiagram} that can be rasterized into a bitmap format. The
   * {@link SVGUniverse} class will
   *
   * @param path The full path (starting at the root), relative to the
   *             application or JAR file's resources directory.
   * @return An {@link SVGDiagram} that can be rasterized onto a
   * {@link BufferedImage}.
   */
  private SVGDiagram loadDiagram( final String path ) {
    final var url = getResourceUrl( path );
    final var uri = sRenderer.loadSVG( url );
    final var diagram = sRenderer.getDiagram( uri );
    return applySettings( diagram );
  }

  /**
   * Instructs the SVG renderer to rasterize the image even if it would be
   * clipped.
   *
   * @param diagram The {@link SVGDiagram} to render.
   * @return The same instance with ignore clip heuristics set to {@code true}.
   */
  private SVGDiagram applySettings( final SVGDiagram diagram ) {
    diagram.setIgnoringClipHeuristic( true );
    return diagram;
  }

  /**
   * Scales the given source {@link Dimension} to the destination
   * {@link Dimension}, maintaining the aspect ratio with respect to
   * the best fit.
   *
   * @param src The original vector graphic dimensions to change.
   * @param dst The desired image dimensions to scale.
   * @return The given source dimensions scaled to the destination dimensions,
   * maintaining the aspect ratio.
   */
  private Dimension fit( final Dimension src, final Dimension dst ) {
    final var srcWidth = src.getWidth();
    final var srcHeight = src.getHeight();

    // Determine the ratio that will have the best fit.
    final var ratio = Math.min(
        dst.getWidth() / srcWidth, dst.getHeight() / srcHeight
    );

    // Scale both dimensions with respect to the best fit ratio.
    return new Dimension( (int) (srcWidth * ratio), (int) (srcHeight * ratio) );
  }
}

使用SvgRasterizer如下：

final var rasterizer = new SvgRasterizer();
final var image = rasterizer.rasterize( "/images/icon.svg", new Dimension( 200, 200 ) );

该图像可以毫不费力地添加到 Swing 组件中。例如，这是一个JComponent可以像其他任何东西一样处理的：

import javax.swing.*;
import java.awt.*;

/**
 * Responsible for drawing an image, which can be changed at any time.
 */
public class ImageComponent extends JComponent {
  /**
   * Mutable image.
   */
  private Image mImage;

  ImageComponent( final Image image ) {
    mImage = image;
  }

  @Override
  public Dimension getPreferredSize() {
    // Race-condition guard.
    final var image = mImage;

    return new Dimension(
        image.getWidth( null ), image.getHeight( null )
    );
  }

  @Override
  protected void paintComponent( final Graphics graphics ) {
    super.paintComponent( graphics );

    final var g = (Graphics2D) graphics.create();
    g.drawImage( mImage, 0, 0, this );
  }

  /**
   * Repaints this component using the given image. This is a mutable
   * operation that changes the internal {@link Image} instance.
   *
   * @param image The new image to use for painting.
   */
  public void redraw( final Image image ) {
    mImage = image;
    repaint();
  }
}