java图片压缩

看了一些网上的代码，总觉得，是在计算机出长和宽，起始坐标后 裁减了原图片，到底能不能实现压缩，比如：原图的大小为 310*330 我现在想把长固定为220然后宽压缩为 220/310*330 的效果？

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用imagemagick的效果好。不过用起来不是很方便。在linux下倒还方便。在win下用就没那么方便了。
对效果要求不高可以用awt来缩放就可以了。

public final class ThumbUtils {

	private ThumbUtils() {
	}

	/**
	 * @param in
	 * @param out
	 * @param formatName
	 * @param size
	 * @throws IOException
	 */
	public static void encodeThumb(InputStream in, OutputStream out, PictureSize limitSize, String formatName) throws IOException {
		BufferedImage image = ImageIO.read(in);
		encodeThumb(image, out, limitSize, formatName);
	}

	public static void encodeThumb(BufferedImage image, OutputStream out, PictureSize limitSize, String formatName) throws IOException {
		PictureSize originalSize = new PictureSize(image.getWidth(null), image.getHeight(null));
		PictureSize thumbSize = getThumbSize(limitSize, originalSize);
		int width = thumbSize.getWidth(), height = thumbSize.getHeight();

		ColorModel dstCM = image.getColorModel();
		BufferedImage dst = new BufferedImage(dstCM, dstCM.createCompatibleWritableRaster(width, height), dstCM.isAlphaPremultiplied(), null);

		Image scaleImage = image.getScaledInstance(width, height, Image.SCALE_SMOOTH);
		Graphics2D g = dst.createGraphics();
		g.drawImage(scaleImage, 0, 0, width, height, null);
		g.dispose();

		ImageIO.write(dst, formatName, out);
	}

	/**
	 * @param limitSize
	 * @param originalSize
	 * @return
	 */
	public static PictureSize getThumbSize(PictureSize limitSize, PictureSize originalSize) {

		int maxWidth = limitSize.getWidth();
		int maxHeight = limitSize.getHeight();
		if (maxWidth == 0 && maxHeight == 0) {
			maxWidth = maxHeight = DEFAULT_THUMB_SIZE;
		}
		int originalWidth = originalSize.getWidth();
		int originalHeight = originalSize.getHeight();
		int width = DEFAULT_THUMB_SIZE, height = DEFAULT_THUMB_SIZE;
		float rate = 0;
		if (maxWidth > 0 && maxHeight > 0) {
			rate = Math.min(maxWidth * 1f / originalWidth, maxHeight * 1f / originalHeight);
		} else if (maxWidth > 0) {
			rate = maxWidth * 1f / originalWidth;
		} else if (maxHeight > 0) {
			rate = maxHeight * 1f / originalHeight;
		} else {
			// no happen.
		}
		width = (int) (originalWidth * rate);
		height = (int) (originalHeight * rate);
		return new PictureSize(width, height);

	}

	public static final int DEFAULT_THUMB_SIZE = 96;

}

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jmagick ( http://www.jmagick.org/index.html )，imagemagick的Java实现。可以用

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淘宝网使用GraphicsMagick处理图片，据说比imagemagick更高效，Java API：im4java。

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php的GD库毫无压力的做到……imagemagick当然也行了，其java实现就是@gaosboy所说的jmagick拉。