java高质量图片缩放

/**
	 * 图片缩放
	 * @param originalFile 源文件
	 * @param resizedFile 目标文件
	 * @param newWidth 新图片的宽度
	 * @param quality 成像质量
	 * @throws IOException
	 */
	public static void resize(File originalFile, File resizedFile,
			int newWidth, float quality) throws IOException {

		if (quality > 1) {
			throw new IllegalArgumentException(
					"Quality has to be between 0 and 1");
		}

		ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
		Image i = ii.getImage();
		Image resizedImage = null;

		int iWidth = i.getWidth(null);
		int iHeight = i.getHeight(null);

		if (iWidth > iHeight) {
			resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight)
					/ iWidth, Image.SCALE_AREA_AVERAGING);
		} else {
			resizedImage = i.getScaledInstance((newWidth * iWidth) / iHeight,
					newWidth, Image.SCALE_AREA_AVERAGING);
		}

		// This code ensures that all the pixels in the image are loaded.
		Image temp = new ImageIcon(resizedImage).getImage();

		// Create the buffered image.
		BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null),

		temp.getHeight(null), BufferedImage.TYPE_INT_RGB);

		// Copy image to buffered image.
		Graphics g = bufferedImage.createGraphics();

		// Clear background and paint the image.
		g.setColor(Color.white);
		g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
		g.drawImage(temp, 0, 0, null);
		g.dispose();

		// Soften.
		float softenFactor = 0.05f;
		float[] softenArray = { 0, softenFactor, 0, softenFactor,
				1 - (softenFactor * 4), softenFactor, 0, softenFactor, 0 };
		Kernel kernel = new Kernel(3, 3, softenArray);
		ConvolveOp cOp = new ConvolveOp(kernel,

		ConvolveOp.EDGE_NO_OP, null);
		bufferedImage = cOp.filter(bufferedImage, null);

		// Write the jpeg to a file.
		FileOutputStream out = new FileOutputStream(resizedFile);

		// Encodes image as a JPEG data stream
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

		JPEGEncodeParam param = encoder
				.getDefaultJPEGEncodeParam(bufferedImage);

		param.setQuality(quality, true);

		encoder.setJPEGEncodeParam(param);
		encoder.encode(bufferedImage);
	}

Image.SCALE_AREA_AVERAGING为缩放算法，可根据需求查API选择不同的缩放算法。