Kent C. Dodds

  /**
  * This method resizes the given image using Image.SCALE_SMOOTH.
  *
  * @param image the image to be resized
  * @param width the desired width of the new image. Negative values force the only constraint to be height.
  * @param height the desired height of the new image. Negative values force the only constraint to be width.
  * @param max if true, sets the width and height as maximum heights and widths, if false, they are minimums.
  * @return the resized image.
  */
  public static Image resizeImage(Image image, int width, int height, boolean max) {
    if (width < 0 && height > 0) {
      return resizeImageBy(image, height, false);
    } else if (width > 0 && height < 0) {
      return resizeImageBy(image, width, true);
    } else if (width < 0 && height < 0) {
      PrinterHelper.printErr("Setting the image size to (width, height) of: ("
              + width + ", " + height + ") effectively means \"do nothing\"... Returning original image");
      return image;
      //alternatively you can use System.err.println("");
      //or you could just ignore this case
    }
    int currentHeight = image.getHeight(null);
    int currentWidth = image.getWidth(null);
    int expectedWidth = (height * currentWidth) / currentHeight;
    //Size will be set to the height
    //unless the expectedWidth is greater than the width and the constraint is maximum
    //or the expectedWidth is less than the width and the constraint is minimum
    int size = height;
    if (max && expectedWidth > width) {
      size = width;
    } else if (!max && expectedWidth < width) {
      size = width;
    }
    return resizeImageBy(image, size, (size == width));
  }
 
  /**
  * Resizes the given image using Image.SCALE_SMOOTH.
  *
  * @param image the image to be resized
  * @param size the size to resize the width/height by (see setWidth)
  * @param setWidth whether the size applies to the height or to the width
  * @return the resized image
  */
  public static Image resizeImageBy(Image image, int size, boolean setWidth) {
    if (setWidth) {
      return image.getScaledInstance(size, -1, Image.SCALE_SMOOTH);
    } else {
      return image.getScaledInstance(-1, size, Image.SCALE_SMOOTH);
    }
  }
 
  public static Image resizeImageFromFile(String location, int width, int height, boolean max) throws IOException {
    BufferedImage image = ImageIO.read(new File(location));
    return resizeImage(image, width, height, max);
  }
 
  public static Image resizeImageFromResource(String location, int width, int height, boolean max) throws IOException {
    BufferedImage image = ImageIO.read(SwingHelper.class.getResource(location));
  }