java 截取图片同时设置dpi

可以使用 Java 的 BufferedImage 类来截取图片，同时可以使用 Graphics2D 类来设置 DPI。具体实现可以参考以下代码：

// 读取图片
BufferedImage image = ImageIO.read(new File("image.jpg"));

// 截取图片
BufferedImage subImage = image.getSubimage(x, y, width, height);

// 设置 DPI
Graphics2D g2d = subImage.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_RESOLUTION_VARIANT, RenderingHints.VALUE_RESOLUTION_VARIANT_SIZE_FIT);
g2d.setRenderingHint(RenderingHints.KEY_RESOLUTION_DPI, dpi);

// 保存图片
ImageIO.write(subImage, "jpg", new File("subImage.jpg"));

注意：上述代码中的 x、y、width、height、dpi 都需要根据具体情况进行设置。