JPEG形式の画像の圧縮率を変更する

• JavaでJPEGの圧縮率を変更する方法のサンプルです。
• 指定したサイズになるまで圧縮率を上げていきます。

import java.awt.*;

import java.awt.image.*;

import java.io.*;

import javax.swing.*;

import com.sun.image.codec.jpeg.*;

public class ProgressiveEncoder{

	

	private static final long LN_MAX_FILE_SIZE_IN_BYTE = 65536L;

	

	public static void main(String[] args){

		

		String inFileName = "";

		String outFileName = "out.jpg";

		long maxFileSizeInByte = LN_MAX_FILE_SIZE_IN_BYTE;

		float fqual = 1.0F;

		

		if(args.length >= 3){

			inFileName = args[0];

			outFileName = args[1];

			maxFileSizeInByte = Long.parseLong(args[2]);

			

		}else if (args.length == 2){

			inFileName = args[0];

			outFileName = args[1];

			

		}else if (args.length == 1){

			inFileName = args[0];

		

		}else{

			throw new RuntimeException("パラメータが足りません");

		}

		

		

		try{

			//アプリケーションフレームの作成

			Frame appFrame = new Frame("圧縮中");

			ImageCanvas imgCanvas = new ImageCanvas();

			

			//元画像のロード

			Image img = new ImageIcon(inFileName).getImage();

			

			imgCanvas.setImage(img);

			

			appFrame.setSize(800,600);

			appFrame.add(imgCanvas);

			appFrame.setVisible(true);

			

			

			BufferedImage bi = new BufferedImage(img.getWidth(imgCanvas),img.getHeight(imgCanvas),BufferedImage.TYPE_INT_RGB);

			Graphics graph = bi.getGraphics();

			graph.drawImage(img,0,0,imgCanvas);

			

			JPEGEncodeParam encodeParam = JPEGCodec.getDefaultJPEGEncodeParam(bi);

			OutputStream ostream = new FileOutputStream(outFileName);

			

			//出力ストリームの確保

			for(fqual = 1.00F; fqual > 0.00F; fqual = fqual - 0.01F){
				

				ByteArrayOutputStream baoutStream = new ByteArrayOutputStream();

				

				encodeParam.setQuality(fqual,false);

				

				JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder( baoutStream, encodeParam);

				encoder.encode(bi);

				

				if(baoutStream.size() <= maxFileSizeInByte){

					ostream.write(baoutStream.toByteArray());

					break;

				}
			}

			

			ostream.flush();

			ostream.close();

		}catch(Exception ex){

			ex.printStackTrace();

			System.exit(9);

		}

		

		System.out.println("Quality=" + fqual);

		System.exit(0);

	}

	

}
class ImageCanvas extends Canvas{

	

	private Image image_;

	

	public ImageCanvas(){

		super();

		

	}

	

	public void setImage(Image img){

		image_ = img;

	}

	

	public void paint(Graphics g){

		if(image_ != null){

			g.drawImage(image_,0,0,this);

		}

	}

	

}