Java ImageIO IIOException: Unsupported image type?

问题

Working with images in Java for the first time and am getting some bizarro exceptions that aren't documented very well. Here's the line of code that is failing:

BufferedImage imgSelected = ImageIO.read(new File("/abs/url/to/file/image.jpg"));

This line is throwing an IIOException with Unsupported image type as the exception message. I have checked and re-checked that it is in fact this line throwing the exception, that the File object is valid, that the URL is valid, and that the image.jpg is in fact a valid JPG that loads perfectly fine in other image viewers.

What could I do to get more information about the nature of this exception? Is this the traditional way for loading images in Java 7, or is this an old/deprecating method? There's just not a lot of info out there about these "Unsupported image type" exceptions, and surely, ImageIO supported JPGs!

Thanks for any help!

回答1:

Try to check the encoding of the JPEG. ImageIO can't read CMYK-encoded jpeg images for example. AFAIK, ImageIO hasn't been updated for years, so you'd like to try and use the official alternative/extension: JAI ImageIO.

Unforutnately, JAI ImageIO needs some native libraries installed into the JRE, which might be unwanted. We do the following:

use Apache Sanselan to detect, whether it's a JPEG
since Sanselan can't read and write JPEG, use the plain old AWT JPEGCodec: JPEGCodec.createJPEGDecoder(...)
to convert CMYK to RGB, we then get the raster of the read BufferedImage and manually convert it (you could use ICC profiles, but the manual conversion fits our needs)

Here's a question of mine that resulted of the fact that ImageIO doesn't support all types of JPEG images, and I there stated a little more of my findings of why you get that message: Pure Java alternative to JAI ImageIO for detecting CMYK images

回答2:

I've unfortunately come across a lot of standard violating JPEG files. ImageIO is particularly picky and often refuse to load images, which are often loaded and apparently displayed correctly by other software with less strict checks on the file format.

It's not very pretty, but one workaround is to use the Oracle VM internal JPEG decoder directly (com.sun.image.codec.jpeg.JPEGCodec), as it seems to tolerate more spec deviations as the ImageIO wrapper:

BufferedImage img = 
    JPEGCodec.createJPEGDecoder(inputStream).decodeAsBufferedImage();

This is of course not an ideal solution, since using implementation specific classes will lock you to a specific VM vendor and may break with newer VM versions, but if you'll only used the software in a controlled environment, it may be better than no solution at all.