java等比壓縮圖檔

等比壓縮圖檔

上傳新聞時，為了避免圖檔太大，需要等比壓縮圖檔，适當壓縮并不影響圖檔在浏覽器中展示。一般建議不超過500k。

1. 示例代碼

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageOutputStream;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;

public class DipUtil {
    /**
     * 自動壓縮圖檔,總大小不超過500k
     * @param source
     * @param target
     * @throws IOException
     */
    public static void compressInLimit(File source,File target) throws IOException{
        long sourceSize = source.length();
        float ratio = (float) Math.log10(sourceSize/);
        if (ratio <= )
            ratio = f;
        else if (ratio >  && ratio <  )
            ratio = -((sourceSize/)/)*f;
        else
            ratio = (sourceSize/)/;

        System.out.println(ratio);

        BufferedImage bufferedImage = ImageIO.read(source);
        OutputStream  outputStream  = new FileOutputStream(target);

        // 建構ImageWriter
        Iterator<ImageWriter> writers =  ImageIO.getImageWritersByFormatName("jpg");
        ImageWriter writer = writers.next();
        ImageOutputStream ios = ImageIO.createImageOutputStream(outputStream);
        writer.setOutput(ios);

        // 設定參數
        ImageWriteParam param = writer.getDefaultWriteParam();
        param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
        param.setCompressionQuality(ratio);

        writer.write(null, new IIOImage(bufferedImage, null, null), param);

        outputStream.close();
        ios.close();
        writer.dispose();
    }

    public static void main(String[] args) throws IOException {
        File source = new File("e:/0139.jpg");
        File target = new File("e:/0140.jpg");

        compressInLimit(source,target);
    }
}
           

1. 總結

   Digital Image Processing (DIP) 數字圖形處理聚焦計算機能夠開發處理圖像，輸入是數字圖像，使用有效的算法，輸出為我們想要的圖像。java提供了友善快捷的API，可以輕松實作各種圖像處理，如：灰階處理、增強、壓縮、增加邊框、高斯模糊、增加水印等。

   本文僅舉例說明了壓縮，可以看出非常簡單好用。