Detecting image encoding in Java

Question

I'm accepting an image as input from the user. I want to only allow a JPEG image. The image is arriving as an InputStream (called myInputStream below). In the code below, the Iterator returned by ImageIO.getImageReaders() is always empty.

ImageInputStream imageInputStream = ImageIO.createImageInputStream(
    myInputStream);
Iterator<ImageReader> iter = ImageIO.getImageReaders(imageInputStream);
if (!iter.hasNext()) {
    // this always happens
}
ImageReader reader = (ImageReader) iter.next();
if (!reader.getFormatName().equals("jpeg")) {
    // haven't got this far yet
}

I have also tried passing myInputStream directly to ImageIO.getImageReaders() with the same result.

write you OS and JDK versions. On my ubuntu 10.04 with OpenJDK 6, `ImageIO.getImageReaders` returns an instance of `com.sun.imageio.plugins.jpeg.JPEGImageReader` — Denis Tulskiy, Dec 25 '10 at 13:56
It's Mac OS X 10.6 with JDK 1.6 (the default version that comes with OS X) — alexantd, Dec 25 '10 at 14:28
seems like mac osx does not support advanced java imaging http://forums.java.net/node/669174 — Denis Tulskiy, Dec 25 '10 at 16:53

score 5 · Accepted Answer · edited May 23 '17 at 11:51

5

An empty iterator usually means ImageIO hasn't found a good image reader for decoding your image. This may be because you'are missing the right decoder in your classpath, or you image has an unsupported color model.

edited May 23 '17 at 11:51

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answered Dec 25 '10 at 13:31

rodion

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Detecting image encoding in Java

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