Compress JPEG to 100kb

Question

What is the general approach to compress an image to JPEG with a target 100kb size? Either lowering the "bitrate", automatically resizing the image, both?

That is, using pure Java and no external "native" dependencies.

Answer 1

Another option is to use: https://github.com/fewlaps/slim-jpg

Result result = SlimJpg.file(imageBytes)
                .maxVisualDiff(0.5)
                .maxFileWeightInKB(100)
                .deleteMetadata()
                .optimize();
byte[] compressedBytes = result.getPicture();

Answer 2

You can use the Java ImageIO package to do the compression using pure Java. You have the documentaion here: javax.imageio

Here is an example how to use it, the example is from this thread if you want to read more about it: How can I compress images using java?

import java.awt.image.BufferedImage;
import java.io.*;
import java.util.Iterator;
import javax.imageio.*;
import javax.imageio.stream.*;

public class Compresssion {

  public static void main(String[] args) throws IOException {

    File input = new File("original_image.jpg");
    BufferedImage image = ImageIO.read(input);

    File compressedImageFile = new File("compressed_image.jpg");
    OutputStream os = new FileOutputStream(compressedImageFile);

    Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("jpg");
    ImageWriter writer = (ImageWriter) writers.next();

    ImageOutputStream ios = ImageIO.createImageOutputStream(os);
    writer.setOutput(ios);

    ImageWriteParam param = writer.getDefaultWriteParam();

    param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    param.setCompressionQuality(0.05f);  // Change the quality value you prefer
    writer.write(null, new IIOImage(image, null, null), param);

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