Java swing高质量PNG

Question

我一直在尝试将我的swing 2d图表导出为png文件。我尝试了以下代码：

BufferedImage bufferedImage = new BufferedImage(width,height,BufferedImage.TYPE_INT_ARGB);
Graphics2D referenceGraphics = bufferedImage.createGraphics();
referenceGraphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
paintComponent(referenceGraphics);

File imageFile = new File(fileName);
if (imageFile.exists() || imageFile.createNewFile()) {
    ImageIO.write(bufferedImage, "png", imageFile);
}

然而，png文件创建成功，但质量太低。我需要创建至少300ppi的图像文件。如何做到这一点呢？

Answer 1

简单地增加组件的大小并不会使图像的分辨率更好。它只会更大。您需要做的是创建比组件更大的BufferedImage (即3倍于当前分辨率的3倍)，并缩放BufferedImage的Graphics对象。生成的代码将如下所示：

public static void main(String[] args) throws IOException {
    Component comp = ...
    BufferedImage img = scaledImageFromComponent(comp, 3);
    File imageFile = new File(fileName);
    if (imageFile.exists() || imageFile.createNewFile()) {
        ImageIO.write(img, "png", imageFile);
    }
}

public static BufferedImage scaledImageFromComponent(final Component c, final double scale) {
    c.setSize(c.getPreferredSize());
    c.doLayout();
    Rectangle r = new Rectangle(0, 0, c.getWidth(), c.getHeight());
    return scaledImageFromComponent(c, r, scale, scale, false);
}

public static BufferedImage scaledImageFromComponent(final Component c, final Rectangle bounds,
                                                     final double scalex, final double scaley,
                                                     final boolean print) {
    BufferedImage image = createCompatibleTransparentImage((int) (scalex * bounds.width),
                                                           (int) (scaley * bounds.height));
    final Graphics2D g2d = (Graphics2D) image.getGraphics();
    g2d.scale(scalex, scaley);
    g2d.translate(-bounds.x, -bounds.y);
    if (print) {
        c.print(g2d);
    } else {
        c.paint(g2d);
    }
    g2d.dispose();
    return image;
}

public static BufferedImage createCompatibleTransparentImage(final int width,
                                                             final int height) {
    return isHeadless() ? new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB)
                        : getGraphicsConfiguration().createCompatibleImage(width, height,
                                                                           Transparency.BITMASK);
}

private static boolean isHeadless() {
    return GraphicsEnvironment.isHeadless();
}

private static GraphicsConfiguration getGraphicsConfiguration() {
    return GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
}

如果您的图表包含文本，您可能希望将Transparency.BITMASK与Transparency.OPAQUE进行切换，以获得更好的抗锯齿支持(在Windows上)。