重新調整影像大小

ResizeImage

import java.awt.image.BufferedImage;
import java.awt.Image;
import java.io.IOException;
import java.io.OutputStream;
import javax.imageio.ImageIO;

public class ResizeImage {

  public static void resize(BufferedImage bufferedImage, int maxEdge, OutputStream os) throws IOException {
    int w = bufferedImage.getWidth();
    int h = bufferedImage.getHeight();
    double factor = w >= h && w > maxEdge ? maxEdge * 1.0 / w : h > maxEdge ? maxEdge * 1.0 / h : 1;
    Image rescaled = bufferedImage.getScaledInstance(w > h ? 500 : Long.valueOf(Math.round(w * factor)).intValue(),
      h > w ? 500 : Long.valueOf(Math.round(h * factor)).intValue(), Image.SCALE_AREA_AVERAGING);
    bufferedImage = new BufferedImage(w > h ? 500 : Long.valueOf(Math.round(w * factor)).intValue(),
      h > w ? 500 : Long.valueOf(Math.round(h * factor)).intValue(), BufferedImage.TYPE_INT_ARGB);
    java.awt.Graphics2D g = bufferedImage.createGraphics();
    g.drawImage(rescaled, 0, 0, null);
    g.dispose();
    ImageIO.write(bufferedImage, "png", os);
  }
}