Donno if you know about the JPEG Redaction lib from ObscuraCam. Its in C++, unfortunately, but might have useful approaches in it:
https://github.com/guardianproject/ObscuraCam/tree/master/app/src/main/jni .hc Michael Rogers: > That doesn't look easy, unfortunately. The class seems to be designed to > work in three stages: > > 1. Load the EXIF data from a file or input stream > 2. Modify the EXIF data > 3. Write the modified image to an output stream by reading the input a > second time and replacing the EXIF segment > > We can't skip to stage 3 because it depends on state that was > initialised during stage 1. Even if we don't care about the original > EXIF data, some of the state seems like it would be vital, such as the > byte order and colour space. > > Maybe we could use a giant BufferedInputStream big enough to hold the > whole image, allowing us to read the stream twice? > > Cheers, > Michael > > On 28/03/18 19:43, Hans-Christoph Steiner wrote: >> >> Ah cool! It would be awesome to have the EXIF stripping work on a >> stream, rather than a file. >> >> .hc >> >> Michael Rogers: >>> Fantastic! >>> >>> The code is just a single file with minimal Android dependencies, so I >>> made a quick (untested) Java port: >>> >>> https://code.briarproject.org/akwizgran/metadata >>> >>> Cheers, >>> Michael >>> >>> On 26/03/18 22:32, Hans-Christoph Steiner wrote: >>>> >>>> Turns out Google released an Android Support library that makes it >>>> trivial to strip EXIF from JPEGs and some RAW formats: >>>> https://android-developers.googleblog.com/2016/12/introducing-the-exifinterface-support-library.html >>>> >>>> I found it via this app in F-Droid: >>>> https://gitlab.com/juanitobananas/scrambled-exif >>>> >>>> This is all it does: >>>> ExifInterface exifInterface = new ExifInterface(imagePath); >>>> for (String attribute : getExifAttributes()) { >>>> if (exifInterface.getAttribute(attribute) != null) { >>>> exifInterface.setAttribute(attribute, null); >>>> } >>>> exifInterface.saveAttributes(); >>>> >>>> .hc >>>> >>>> Michael Rogers: >>>>> Please feel free to use it, I place it in the public domain. I'll have a >>>>> look at JPEGs next time I'm procrastinating. ;-) >>>>> >>>>> (By the way, after sending I noticed a bug: if the file ends with a >>>>> truncated ancillary chunk, I think the cleaner will loop forever trying >>>>> to skip to the end of the chunk. Should be easy to fix though.) >>>>> >>>>> Cheers, >>>>> Michael >>>>> >>>>> On 13/12/17 13:02, Hans-Christoph Steiner wrote: >>>>>> >>>>>> That's awesome! Feeling inspired to also strip JPEGs? :-) I think >>>>>> they're easier. There is jhead, exiftool, and ObscuraCam's JNI code for >>>>>> examples. Can we use this under the GPLv3? >>>>>> >>>>>> .hc >>>>>> >>>>>> Michael Rogers: >>>>>>> Hi Hans-Christoph, >>>>>>> >>>>>>> I hacked this together based on the PNG specification, which >>>>>>> distinguishes between ancillary chunks that can be removed without >>>>>>> affecting the image data, and critical chunks that can't. It's been >>>>>>> tested on exactly two PNGs so far. :-) >>>>>>> >>>>>>> http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html >>>>>>> >>>>>>> Cheers, >>>>>>> Michael >>>>>>> >>>>>>> On 12/12/17 16:25, Hans-Christoph Steiner wrote: >>>>>>>> >>>>>>>> pyexiftool is just a wrapper for exiftool. exiftool looks great, but >>>>>>>> for my use case, I only need to strip all metadata. It would be much >>>>>>>> easier if that was in pure Python and pure Java. perl is a no go on >>>>>>>> Android. >>>>>>>> >>>>>>>> It was dead simple to strip EXIF from JPEG in Python: >>>>>>>> >>>>>>>> from pil import Image >>>>>>>> with open(inpath) as fp: >>>>>>>> in_image = Image.open(fp) >>>>>>>> data = list(in_image.getdata()) >>>>>>>> out_image = Image.new(in_image.mode, in_image.size) >>>>>>>> out_image.putdata(data) >>>>>>>> out_image.save(outpath) >>>>>>>> >>>>>>>> But that broke some PNGs, and the rest were larger in size. >>>>>>>> >>>>>>>> .hc >>>>>>>> >>>>>>>> Rick Valenzuela: >>>>>>>>> oh, you may already know this, but the previous code keeps a copy of >>>>>>>>> the >>>>>>>>> file and metadata. if you want it gone with no copies, you have to >>>>>>>>> add a >>>>>>>>> switch to overwrite, e.g.: >>>>>>>>> >>>>>>>>> ``` >>>>>>>>> with exiftool.ExifTool() as et: >>>>>>>>> et.execute(b'-all=', b'-overwrite_original', b'some.png') >>>>>>>>> ``` >>>>>>>>> >>>>>>>>> On 12/12/2017 23:45, Rick Valenzuela wrote: >>>>>>>>>> heh, nice -- I just found this: >>>>>>>>>> >>>>>>>>>> https://github.com/smarnach/pyexiftool >>>>>>>>>> >>>>>>>>>> Tried it out and it worked great: >>>>>>>>>> ``` >>>>>>>>>> with exiftool.ExifTool() as et: >>>>>>>>>> et.execute(b'-all=', b'some.png') >>>>>>>>>> ``` >>>>>>>>>> >>>>>>>>>> On 12/12/2017 19:53, Hans-Christoph Steiner wrote: >>>>>>>>>>> >>>>>>>>>>> Ah, cool, I thought exiftool only worked with JPEGs. It seems to >>>>>>>>>>> work >>>>>>>>>>> with just about every image format. Now the open question is how to >>>>>>>>>>> strip all PNG metadata with Python and Java. >>>>>>>>>>> >>>>>>>>>>> .hc >>>>>>>>>>> >>>>>>>>>>> Rick Valenzuela: >>>>>>>>>>>> does exiftool do what you need? >>>>>>>>>>>> >>>>>>>>>>>> `exiftool -all= <some.PNG>` >>>>>>>>>>>> >>>>>>>>>>>> On 11/12/2017 17:57, Hans-Christoph Steiner wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> Anyone know any tools for sanitizing PNGs without touching the >>>>>>>>>>>>> compressed image data? With JPEG it is easy to strip out EXIF >>>>>>>>>>>>> with >>>>>>>>>>>>> python-pil or many other tools. I haven't found a simple, clean >>>>>>>>>>>>> approach >>>>>>>>>>>>> in Python for PNGs. >>>>>>>>>>>>> >>>>>>>>>>>>> .hc >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>> >>>> >> -- PGP fingerprint: EE66 20C7 136B 0D2C 456C 0A4D E9E2 8DEA 00AA 5556 https://pgp.mit.edu/pks/lookup?op=vindex&search=0xE9E28DEA00AA5556 _______________________________________________ List info: https://lists.mayfirst.org/mailman/listinfo/guardian-dev To unsubscribe, email: guardian-dev-unsubscr...@lists.mayfirst.org
