Support for TIFF with LZW with more than 12 bits per code

[michal-niklas]

Hello,

One of TIFF images I tried to open with your plugin failed with exception:

com.twelvemonkeys.io.enc.DecodeException: TIFF LZW with more than 12 bits per code encountered (table overflow)
at com.twelvemonkeys.imageio.plugins.tiff.LZWDecoder.addStringToTable(Unknown Source)
at com.twelvemonkeys.imageio.plugins.tiff.LZWDecoder.decode(Unknown Source)
at com.twelvemonkeys.io.enc.DecoderStream.fill(Unknown Source)
at com.twelvemonkeys.io.enc.DecoderStream.read(Unknown Source)
at java.nio.channels.Channels$ReadableByteChannelImpl.read(Channels.java:385)
at com.twelvemonkeys.imageio.plugins.tiff.HorizontalDeDifferencingStream.fetch(Unknown Source)
at com.twelvemonkeys.imageio.plugins.tiff.HorizontalDeDifferencingStream.read(Unknown Source)
at java.io.DataInputStream.readFully(DataInputStream.java:195)
...

This TIFF opens without problems with GIMP, Krusader preview or with Pythons PIL library. It seems to be grayscale, 8 bits per pixel, LZW compression.

[haraldk]

Hi Michal,

Thanks for reporting!

Strange. More than 12 bits per code, usually means an error in the encoder or decoder, as this would normally lead to an unreasonably large dictionary, and can easily be avoided by resetting the dictionary... But.. Could be my decoder. ;-)

Can you send me the file in question? Either as a link (dropbox or similar), or as an attachment in an email. If you do that, I'll have a look at it! :-)

Regards,

Harald K

[haraldk]

Hi,

Thanks for providing a sample. I can reproduce the problem.

I can also read it fine, if I enable the "compatibility" mode of the LZW-decoder, there's just no way to do that other than changing the code at the moment...

If you're in a hurry, you can try changing LZWDecoder.java (around line 196):

    protected LZWSpecDecoder() {
        super(true); // Used to be false, set to true to use compatibility mode
    }

In any case, I'll look into it, and hope to have a fix available soon.

Best regards,

Harald K

[haraldk]

Fixed in 27b2ff3.

Harald K

[michal-niklas]

I have just compiled it and it works. Thank you!

[haraldk]

FYI: This fix is included in the 3.0.2 release, and will be on Maven Central in a few hours. :-)

Harald K