NullPointerException with embedmark command for some valid images

[alexvanbelle]

Hi,

First, just want to say thank you for the great work on Openstego! Really appreciated.

I try to use it for a big image dataset and I notice an unexpected behavior : some valid images can create NullPointerException. I "successfully" reproduce it every time with command line. I didn't test with GUI.

Stack trace:

com.openstego.desktop.OpenStegoException: java.lang.NullPointerException at com.openstego.desktop.OpenStego.embedMark(OpenStego.java:156) at com.openstego.desktop.OpenStego.embedMark(OpenStego.java:178) at com.openstego.desktop.OpenStegoCmd.executeEmbedMark(OpenStegoCmd.java:251) at com.openstego.desktop.OpenStegoCmd.execute(OpenStegoCmd.java:128) at com.openstego.desktop.OpenStego.main(OpenStego.java:355) Caused by: java.lang.NullPointerException at com.openstego.desktop.plugin.dwtdugad.DWTDugadPlugin.embedData(DWTDugadPlugin.java:123) at com.openstego.desktop.OpenStego.embedMark(OpenStego.java:152) ... 4 more

Repro steps:

• A dataset is attached to this issue. Download and unzip. It contains 4 files (1 txt and 3 jpgs). The txt just provide URL of the image source. Then, the original image (4000x6000) is: "pexels-kübra-arslaner-13386712_original". A first resize (400x600) of the image has been generated and is available: "pexels-kübra-arslaner-13386712_smaller.jpg". Another resize (30x45) is "pexels-kübra-arslaner-13386712_null_pointer.jpg"
• Get Openstego zip to extract its jar
• Generate signature with a random password (eg: FKM3u4Yqiw4etwjvzH5ZCFbNFeWUniSBJRdRdzXy): java -jar openstego.jar --gensig --algorithm=dwtdugad --sigfile=/tmp/sigfile_issue --password=FKM3u4Yqiw4etwjvzH5ZCFbNFeWUniSBJRdRdzXy
• Use signature to embed a mark in original image (no error) : java -jar openstego.jar --embedmark --algorithm=dwtdugad --sigfile=/tmp/sigfile_issue -cf 'pexels-kübra-arslaner-13386712_original.jpg'
• Use signature to embed a mark in first resize image (no error): java -jar openstego.jar --embedmark --algorithm=dwtdugad --sigfile=/tmp/sigfile_issue -cf 'pexels-kübra-arslaner-13386712_smaller.jpg'
• Use signature to embed a mark in the smallest image (null pointer exception): java -jar openstego.jar --embedmark --algorithm=dwtdugad --sigfile=/tmp/sigfile_issue -cf 'pexels-kübra-arslaner-13386712_null_pointer.jpg'

Impact:

• Users don't understand the reason of the failure. (probably too small image)
• When embedmark is used with wildcard on folders, as soon as a single image fails, the remaining images are not watermarked

Expected behavior:

• A graceful and self-explanatory message should be provided
• With wildcard, Openstego "embedmark" should continue to watermark remaining images of the folder.

Software versions:

• openjdk 11.0.16 2022-07-19, OpenJDK Runtime Environment (build 11.0.16+8-post-Ubuntu-0ubuntu118.04), OpenJDK 64-Bit Server VM (build 11.0.16+8-post-Ubuntu-0ubuntu118.04, mixed mode, sharing)
• OpenStego v.0.8.4

openstego_digital_watermark_null_pointer_exception.zip

[syvaidya]

Thank you for excellently written bug report. I'll take a look.

[syvaidya]

Fixed with v0.8.5

[alexvanbelle]

Thanks very much. I'll give a try to the new release this week