生成缩略图

最新推荐文章于 2021-03-15 10:59:39 发布

原创最新推荐文章于 2021-03-15 10:59:39 发布 · 501 阅读

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本文介绍了一种在Java中实现图片等比缩放的方法，并提供了将图片转换为不同格式的功能。通过使用BufferedImage类，文章详细展示了如何根据指定的目标宽度和高度来调整图片尺寸，同时保持原始图片的比例不变。

public static BufferedImage resize(BufferedImage source, int targetW,
   int targetH) {
  // targetW，targetH分别表示目标长和宽
  int type = source.getType();
  BufferedImage target = null;
  double sx = (double) targetW / source.getWidth();
  double sy = (double) targetH / source.getHeight();
  // 这里想实现在targetW，targetH范围内实现等比缩放。如果不需要等比缩放
  // 则将下面的if else语句注释即可
  if (sx > sy) {
   sx = sy;
   targetW = (int) (sx * source.getWidth());
  } else {
   sy = sx;
   targetH = (int) (sy * source.getHeight());
  }
  if (type == BufferedImage.TYPE_CUSTOM) { // handmade
   ColorModel cm = source.getColorModel();
   WritableRaster raster = cm.createCompatibleWritableRaster(targetW,
     targetH);
   boolean alphaPremultiplied = cm.isAlphaPremultiplied();
   target = new BufferedImage(cm, raster, alphaPremultiplied, null);
  } else
   target = new BufferedImage(targetW, targetH, type);
  Graphics2D g = target.createGraphics();
  // smoother than exlax:
  g.setRenderingHint(RenderingHints.KEY_RENDERING,
    RenderingHints.VALUE_RENDER_QUALITY);
  g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
  g.dispose();
  return target;
}

public static void createSmallImage(String fromFileStr, String saveToFileStr,
   int width, int hight) throws Exception {
  BufferedImage srcImage;
  // String ex =
  // fromFileStr.substring(fromFileStr.indexOf("."),fromFileStr.length());
  String imgType = "JPEG";
  if (fromFileStr.toLowerCase().endsWith(".png")) {
   imgType = "PNG";
  }
  // System.out.println(ex);
  File saveFile = new File(saveToFileStr);
  File fromFile = new File(fromFileStr);
  srcImage = ImageIO.read(fromFile);
  if (width > 0 || hight > 0) {
   srcImage = resize(srcImage, width, hight);
  }
  ImageIO.write(srcImage, imgType, saveFile);
}