使用ImageIO.write存储png格式图片性能较差问题

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目前加载一个png格式的图片，做一些绘图工作，发现ImageIO.write存储png性能较差，转为存储jpg格式图片，性能可以提高6,7倍。
代码如下。

package test;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;

import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;

import javax.imageio.ImageIO;

import java.util.Iterator;
import javax.imageio.*;
import javax.imageio.stream.*;

import org.junit.Before;
import org.junit.Test;

/**
 * 加载png格式图片，使用不同方式转为png或者jpg格式的性能对比。
 * */
public class PngJpgImagePerTest {

	private static String PNG = "png";
	private static String JPG = "jpg";

	private static String SimpleSavePNG = "__SimpleSavePNG.png";
	private static String Convert2ArrayAndSavePNG = "__Convert2ArrayAndSavePNG.png";
	private static String NewImageSavePNG = "__NewPNG.png";
	private static String NewImageSaveJPG = "__NewJPG.jpg";
	private static String SaveJPG = "__JPG_quality.jpg";

	/**
	 * 保存文件。
	 * */
	public static void save2File(String filePath, byte[] data) {

		BufferedOutputStream bufferOutput = null;

		try {
			bufferOutput = new BufferedOutputStream(new FileOutputStream(
					new File(filePath)), 1024);

			bufferOutput.write(data);
			bufferOutput.flush();
		} catch (Exception e) {
			throw new RuntimeException(e);
		} finally {
			if (bufferOutput != null) {
				try {
					bufferOutput.close();
				} catch (Exception e) {
					throw new RuntimeException(e);
				}
			}
		}
	}

	/**
	 * load image
	 * */
	public static BufferedImage loadImage(String filePath) {
		try {
			return ImageIO.read(new File(filePath));
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * simple save use ImageIO.write
	 */
	public static void saveImage(BufferedImage image, String format,
			String filePath) {
		try {
			ImageIO.write(image, format, new File(filePath));
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * convert to byte array.
	 * */
	public static byte[] convert2bytes(BufferedImage image, String format) {
		try {
			ByteArrayOutputStream bout = new ByteArrayOutputStream(1024);
			ImageIO.write(image, format, bout);
			byte[] data = bout.toByteArray();
			return data;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * create new buffer image and save using png format.
	 * */
	public static void savePngImage(BufferedImage image, String format,
			String filePath) {
		BufferedImage bufferedImage = new BufferedImage(image.getWidth(), image
				.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
		bufferedImage.getGraphics().drawImage(image, 0, 0, null);
		saveImage(bufferedImage, PNG, filePath);
	}

	/**
	 * create new buffer image and save using jpg format.
	 * */
	public static void saveJpgImage(BufferedImage image, String format,
			String filePath) {
		BufferedImage bufferedImage = new BufferedImage(image.getWidth(), image
				.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
		bufferedImage.getGraphics().drawImage(image, 0, 0, null);
		saveImage(bufferedImage, JPG, filePath);
	}

	/**
	 * save jpg with specified quality. 为了图片质量，quality的值不能太低。
	 * */
	public static void saveImageUsingJPGWithQuality(BufferedImage image,
			String filePath, float quality) throws Exception {

		BufferedImage newBufferedImage = new BufferedImage(image.getWidth(),
				image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
		newBufferedImage.getGraphics().drawImage(image, 0, 0, null);

		Iterator iter = ImageIO
				.getImageWritersByFormatName("jpeg");

		ImageWriter imageWriter = iter.next();
		ImageWriteParam iwp = imageWriter.getDefaultWriteParam();

		iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
		iwp.setCompressionQuality(quality);

		File file = new File(filePath);
		FileImageOutputStream fileImageOutput = new FileImageOutputStream(file);
		imageWriter.setOutput(fileImageOutput);
		IIOImage iio_image = new IIOImage(newBufferedImage, null, null);
		imageWriter.write(null, iio_image, iwp);
		imageWriter.dispose();
	}

	public static void drawString(Graphics2D g2, String value, int x, int y) {
		Font font = new Font("Arial", Font.BOLD, 16);
		g2.setColor(Color.BLACK);
		g2.setFont(font);
		g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
				RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
		g2.drawString(value, x, y);
	}

	private String sourceFilePath;
	private BufferedImage sourceImage;
	private int loop;
	private float quality;

	@Before
	public void setup() {
		sourceFilePath = "E:\\allencode\\ImgTest\\stat.png";
		sourceImage = loadImage(sourceFilePath);
		loop = 10;
		quality = 0.8F;
		Graphics2D g2 = sourceImage.createGraphics();
		draw(g2);
	}

	private void draw(Graphics2D g2) {
		drawString(g2, "Allen Hello world.", 500, 200);
	}

	/**
	 * ImageIO.write存储图片时主要的性能消耗在计算上。
	 * */
	@Test
	public void test_01() {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < loop; i++) {
			long start = System.currentTimeMillis();
			saveImage(sourceImage, PNG, sourceFilePath + SimpleSavePNG);
			long end = System.currentTimeMillis();
			sb.append(" saveImage = " + (end - start));

			long convertStart = System.currentTimeMillis();
			byte[] pngData = convert2bytes(sourceImage, PNG);
			long convertEnd = System.currentTimeMillis();
			sb.append(" convert = " + (convertEnd - convertStart));

			long saveStart = System.currentTimeMillis();
			save2File(sourceFilePath + Convert2ArrayAndSavePNG, pngData);
			long saveEnd = System.currentTimeMillis();
			sb.append(" save = " + (saveEnd - saveStart));

			sb.append("\n");
		}

		System.out.println(sb);
	}

	/**
	 * ImageIO.write和新建一个BufferedImage，采用jpg或png保存的比较。
	 * */
	@Test
	public void test_02() {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < loop; i++) {
			long start = System.currentTimeMillis();
			saveImage(sourceImage, PNG, sourceFilePath + SimpleSavePNG);
			long end = System.currentTimeMillis();
			sb.append(" saveImage = " + (end - start));

			start = System.currentTimeMillis();
			savePngImage(sourceImage, "png", sourceFilePath + NewImageSavePNG);
			end = System.currentTimeMillis();
			sb.append(" savePngImage = " + (end - start));

			start = System.currentTimeMillis();
			saveJpgImage(sourceImage, "jpg", sourceFilePath + NewImageSaveJPG);
			end = System.currentTimeMillis();
			sb.append(" saveJpgImage = " + (end - start));

			sb.append("\n");
		}

		System.out.println(sb);
	}

	/**
	 * ImageIO.write存储图片和保存jpg的时间对比。
	 * */
	@Test
	public void test_03() throws Exception {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < loop; i++) {
			long pngStart = System.currentTimeMillis();
			saveImage(sourceImage, PNG, sourceFilePath + SimpleSavePNG);
			long pngEnd = System.currentTimeMillis();
			sb.append(" saveImage = " + (pngEnd - pngStart));

			long jpgStart = System.currentTimeMillis();
			saveImageUsingJPGWithQuality(sourceImage, sourceFilePath + SaveJPG,
					quality);
			long jpgEnd = System.currentTimeMillis();
			sb.append(" JPGWithQuality = " + (jpgEnd - jpgStart));

			sb.append(" % = " + (pngEnd - pngStart) * 1D / (jpgEnd - jpgStart));
			sb.append("\n");
		}

		System.out.println(sb);
	}
}