Java: BufferedImage to byte array and back

Question

I see that a number of people have had a similar problem, however I'm yet to try find exactly what I'm looking for.

So, I have a method which reads an input image and converts it to a byte array:

    File imgPath = new File(ImageName);
    BufferedImage bufferedImage = ImageIO.read(imgPath);
    WritableRaster raster = bufferedImage .getRaster();
    DataBufferByte data   = (DataBufferByte) raster.getDataBuffer();

What I now want to do is convert it back into a BufferedImage (I have an application for which I need this functionality). Note that "test" is the byte array.

    BufferedImage img = ImageIO.read(new ByteArrayInputStream(test));
    File outputfile = new File("src/image.jpg");
    ImageIO.write(img,"jpg",outputfile);

However, this returns the following exception:

    Exception in thread "main" java.lang.IllegalArgumentException: im == null!

This is because the BufferedImage img is null. I think this has something to do with the fact that in my original conversion from BufferedImage to byte array, information is changed/lost so that the data can no longer be recognised as a jpg.

Does anyone have any suggestions on how to solve this? Would be greatly appreciated.

Kurru · Accepted Answer · 2014-08-08 03:28:33Z

133

This is recommended to convert to a byte array

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(img, "jpg", baos);
byte[] bytes = baos.toByteArray();

edited Aug 8, 2014 at 3:28

Kurru

14.4k18 gold badges67 silver badges87 bronze badges

answered Mar 14, 2013 at 16:11

Nikolay Kuznetsov

9,61912 gold badges61 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Christophe Roussy Over a year ago

Flush and close will do nothing

hguser Over a year ago

Is there a special reason to use jpg here?

user207421 Over a year ago

And if close() didn't do anything it would call flush() itself, and it would be necessary to call itbefore toByteArray(), not after it.

Community · Accepted Answer · 2020-06-20 09:12:55Z

15

Note that calling close or flush will do nothing, you can see this for yourself by looking at their source/doc:

Closing a ByteArrayOutputStream has no effect.

The flush method of OutputStream does nothing.

Thus use something like this:

ByteArrayOutputStream baos = new ByteArrayOutputStream(THINK_ABOUT_SIZE_HINT);
boolean foundWriter = ImageIO.write(bufferedImage, "jpg", baos);
assert foundWriter; // Not sure about this... with jpg it may work but other formats ?
byte[] bytes = baos.toByteArray();

Here are a few links concerning the size hint:

Of course always read the source code and docs of the version you are using, do not rely blindly on SO answers.

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Feb 28, 2014 at 10:49

Christophe Roussy

17.2k5 gold badges94 silver badges87 bronze badges

Collectives™ on Stack Overflow

Java: BufferedImage to byte array and back

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related