Develop Reference

Reading quantization tables of jpeg files on Android

A previous answer provides code for reading the quantization tables of jpeg files in Java. However it uses javax.imageio.ImageIO which, according to this answer, isn't available on the Android platform.
How can I read read the quantization tables of jpeg files on Android in Kotlin or the Java subset available on Android?
edit
I have found the korlibs/korim Kotlin library which seems to read the quantization tables. But I'm still a beginner with Kotlin so I haven't yet figured out how I go from a string with the path to the JPEG file to printing out the quantization table.

I am, unfortunately, not aware of such an API for Android.
However, parsing the JPEG quantization tables aren't that hard... You could probably have a look at my JPEGSegmentUtil and QuantizationTable (originally by Helmut Dersch) classes and adapt them to Android. The mentioned code is available under BSD license.
You would need to replace the javax.imageio.ImageInputStream with a different type, preferably something that implements java.io.DataInput and has proper seek/skip, replace javax.imageio.IIOException with normal IOException, and perhaps a few more tweaks.

If you only need to read quantization tables then the simplest solution would be to implement parsing yourself. Basic sample (in C#; but Java/Kotlin implementation is pretty similar): https://stackoverflow.com/a/46162800/136138
This conversation might also be useful: JPEG file quantization table definition
If you need to do more JPEG-related operations then look at JpegKit that wraps the native libjpeg-turbo library.

Create Multipage TIFF with Commons-Imaging

Im trying to check how to generate TIFF using JAVA libraries. I checked JAI, but it requires native libs that I can't use in my project (it must be platform-independent).
I saw a great library, Apache Commons Imaging that generates successfully TIFF, I tried and ...its good.
But I didnt see any way to create TIFF with several pages.
Is there any way to do this?
Thanks!

You can do it with icafe Java library (disclaimer: I am the author of this library). No dependency on any native stuff. Look at the wiki page for item Create multipage TIFF image for example. You can also control the color type and compression method for different pages. Dithering can be set through parameters in case color quantization is required such as saving images to black and white using CCITT group3/group4 compression. The resulting multipage image from the wiki page can be found here.

How to read/write custom PNG metadata in Android?

I have to associate a couple of text parameters (a UUID and a couple of strings representing integers) to a PNG image in a way they can follow the image when the PNG file is passed from an Android device to another through the Net. This is the typical situation in which I would use a couple of custom auxiliary chuncks (similar to EXIF fields ) to store my data inside the PNG image itself.
Maybe it is just me but the only info I was able to find about reading and writing PNG custom metadata from Java code on Android was this SO post:
Writing image metadata in Java, preferably PNG
that even offers some code (quite verbose, as usual with Java).
Those same SO post refers also to PNGJ: http://code.google.com/p/pngj/
To be honest, I would be happy to not use yet another library in this project.
Does anybody know of others ways to write and read text metadata in a PNG file in Android? Maybe a less verbose way... Maybe a way that does not require a separated library....
Any other source of information? Any tutorial? Any example?
I'm open to use a different (but equivalent) image file format, if needed (JPEG, whatever).
A solution working also on iOS and Windows 8 Phone would be a plus but it is not actually required.

I had to do something similar lately, so I had to study the subject.
Android offers you no option of manipulating png metadata. You will have to use an external library (PNGJ seems like a good option).
In my case, since I am making changes to the Android frameworks, I didn't use an external lib, but made changes to skia (the Android graphics library instead).
If you need more info on that I can give you, but I think it's irrelevant in your case.

Native Java document parser and converter library / linux based document converters

I'm looking for a Java library which can do the following:
parse emails in *.eml or *.msg format for attachments of type DOC,DOCX,JPEG,PNG,GIF,TXT,XLS,XLSX,PPT,PDF and convert the attachmens to the TIFF format.
It can be either open source or a comercial library. Alternatively I'm looking for command line tools for linux doing this. We already tried open office, but there are too many problems with some document formats.
UPDATE:
What I found out by research up to now:
For parsing emails and extracting attachments, JavaMail (http://www.oracle.com/technetwork/java/javamail/index.html) is a good choice.
For converting documents, JodConverter (http://code.google.com/p/jodconverter/) is a confortable library. However it's only a wrapper for open office, so if there are issues with open office (and I do have often trouble with openoffice) to convert a document, you will have them also with JodConcerter.
In conclusion I had no luck (up to now) to find any document conversion library implemented in native java, which handels all common document formats, neither open source or even commercial. It seems to be a real market gap.

RainbowPDF may fit: its a commercial server based conversion tool with Java API.
If you've got a Windows server, have a look at NEEVIA Document Converter Pro. It has some mail functionality.
Apace POI is an interface to read the content of Microsoft Office documents. You will have to code the image generating and layouting components on your own. Nervertheless it reads Outlook MSG format.

Apache POI - the Java API for Microsoft Documents. However I don't know how to easily convert parsed document to TIFF.

May be a mix of different approaches could be useful? Depending on your requirements, could be possible to use several libraries to convert all the formats you need to manage: Microsoft Office, Adobe PDF, some different image formats and simple text files.
I mean, you can create a process that, depending on the type of the file extracted (using Java Mail), you could recognize what kind of format the file has and continue processing with the right conversion mechanism using the suitable library. Then you will idenfity if a file it's an image to convert, try Java Advanced Imaging, if it's a Microsoft Office file, try Apache POI and so on. For managing PDF files, you can try Apache PDFBox it's another good and opensource solution.
By the way, if you are looking not only for a Java approach, may be this thread may help you.
I don't know if there are better commercial solutions than #ChrisGer commented.

Do not waste your time looking at Apache POI, as it can only parse the content of the Office files but is not suitable for rendering it.
Since there are OpenOffice servers available, I suggest you do this. I also know you can easily use DCOM to talk with Microsoft Office apps, maybe a Java->DCOM bridge is more up to the task. However, this is not even recommended by Microsoft (so I suppose the JodConverter thing is equally unstable).

Reading RAW images from Java

Canon/Nikon/other cameras save raw output of their sensor in some of their proprietary formats (.CR2, whatever). Is there any Java library designed to read them and convert into manageable BufferedImages?
I don't reqlly care here about fully customizable conversion similar to ufraw or imagemagick, rather something simple that "just works" for rendering simple previews of such images.

I've been where you are, and I feel for you. Your best bet is to use an Adobe or dcraw-based program to create thumbnails automatically. Temporary DNG files using Adobe's converter may be easier to use.
IF you insist on doing it in Java, you're about to run into a mountain of pain. RAW formats change often, have all sorts of crazy nuances and are intentionally hard to work with. Camera makers want you to use THEIR RAW conversion software, to show the camera's abilities at its best and screw Adobe. The guy behind dcraw found that some are camera manufacturers even use encryption now!
The existing Java libraries are poor -- JRawIO has improved since I last looked at it, but it supports only a fraction of the formats that dcraw does. In addition to the listed libraries, the imagero library may provide the ability to display a thumbnail for your image.
From personal experience, don't even think about writing your own RAW file reader.
I tried to do this with a very simple RAW format once (just a solid array of sensor data, 12 bits per pixel). The dcraw source translates badly to Java. You haven't seen such a nightmare of bit-fiddling ever. Took me days to debug problems with byte alignment and endian-ness.

jrawio is a plugin for Java Image I/O. With it you can read the raster data, the thumbnails and the metadata from the raw image file.

nef and cr2 already contains preview images in jpeg. just find the right offset and the right length to extract it...
Laurent Clevy # lclevy.free.fr/raw
Laurent

Unless you want to write you own file parser/loader (sounds fun imho ;) ), perhaps JMagick will help you. I haven't tried it and it might not work given your target platform since JMagick uses JNI.
UPDATE: dcraw looks like a good resource/reference