Quality loss using ImageIO.write

Question

I have noticied significant quality loss using ImageIO.write, how I can disable automatic compression ?

val baos: ByteArrayOutputStream = new ByteArrayOutputStream
val newBi = new BufferedImage(img.getWidth, img.getHeight, BufferedImage.TYPE_INT_RGB)
val gr = newBi.createGraphics()
gr.drawImage(img, 0, 0, img.getWidth(), img.getHeight(), Color.WHITE, null)
ImageIO.write(newBi, "jpeg", baos)
val b = baos.toByteArray
baos.close()

Answer 1

Use ImageWriter.

ImageWriter writer = ImageIO.getImageWritersByFormatName("jpeg").next();
ImageWriteParam param = writer.getDefaultWriteParam();
param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); // Needed see javadoc
param.setCompressionQuality(1.0F); // Highest quality
writer.write(image);

For non-photo images use .png.

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As @PiotrekDe commented, the following seems more logical.

writer.write(null, new IIOImage(image, null, null), param)

Answer 2

JPEG Cmpression is lossy. But PNG compression is lossless. So, i suggest to write in png format. That means you won't loss quality even if you compress in PNG format. Simple lines:

ImageIO.write(newBI,"png",someOutputStream);

But, if you want it in jpg format with quality, set Quality to 100%. The following code may help you.

    ImageWriter jpgWriter = ImageIO.getImageWritersByFormatName("jpg").next();
    ImageWriteParam jpgWriteParam = jpgWriter.getDefaultWriteParam();
    jpgWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    jpgWriteParam.setCompressionQuality(1f);
    jpgWriter.setOutput(someOutputStream);
     //better to use ImageOutputStream
    jpgWriter.write(null,new IIOImage(yourImage, null, null), jpgWriteParam);