I have some swf files generated with Adobe Flash.
Does anybody know how can I decompress their headers in QT?
I need their size (width and height) , frame rate and frame count.
Thanks
It's not documented if qUncompress requires that all compressed data to be in the QByteArray to decompress it. From the wording of it, it seems to imply that. I would imagine loading some large SWF into memory just to get a few bytes in the header is not practical.
If you can live with loading the whole file into memory, just load the file starting at offset 4 into a QByteArray and flip the byte order of the 1st 4 (SWF is little-endian and qUncompress requires the length to be in big-endian). Subtract 4 from the flipped 32-bit integer. Then call qUncompress.
If loading the whole file is not ideal, you may be better off use the stream functions in zlib directly. That allows you to decompress data piece by piece.
Related
I have the situation where i want to get the raw data contents of a qr code. This qrcode contains data stored in a binary form (i.e. its actually a zip archive, deflate format, so its non text i.e. binary).
I am using the latest version of the zxing library in java 11.
Result.getRawBytes was the obvious first attempt, but it doesnt seem to be delivering what I want. Actually, I am not sure what it supposed to deliver (maybe I just misunderstand the function?). I am kind of at a loss here?
EDIT; the qr code contains a small preamble (14 bytes) which are using UTF-8 and acts as an identifiying header, these 14 bytesa re immediately followed by the payload that consists of compressed data (using the deflate function in java). and the raw bytes are stored here. The whole specification of the contents can be found here (as its an UIC standard); https://www.era.europa.eu/sites/default/files/library/docs/recommendation/era_rec122_tap_tsi_revision_recommendation_technical_document_b12_en.pdf, page 36 and onward for those so inclined.
EDIT 2;
When using Neoreader i get the following set of raw bytes from the QR code;
I have a file (about 100k files, to be specific) containing a data from weather radars - one file is a one radar image. It is a mosaic of data from several radars, creating a map of a reflectivity over whole country.
The files have extension .cmax and I need to convert them to something more useful (eg. array of reflectivities) for further uses.
I have asked data provider how to read those files. They responded:
The standard product format in our system (.cmax) is the internal format of the company that provides us with the software. It consists of an xml and binary part. It can be read by reading as a stream of bytes. Firstly, parse the initial bytes as xml, then treat the rest (BLOBs) as a binary data compressed with the "qt" method. You need to unpack them using a library that supports this compression mode. In general, you have to work a little, but it can be done in virtually any programming language.
The main issue is with the binary part of data. I have tried to decompress it with zlib (googling qt compression it comes out) and reading as a binary data in C++. None of them worked. It also doesn't seem resonable to me to try reading that data as binary in Qt.
The file begins with those lines:
<product version="5.44.5" datetime="2017-01-01T18:00:00" datatype="dBZ" type="cmax" name="CMAX" owner="">
<data time="18:00:00" date="2017-01-01">
Then, there are radars specifications and image details (active radars, min and max reflectivity etc). XML part ends with:
</product>
<!-- END XML -->
<BLOB blobid="0" size="79617" compression="qt">(here are lots of binary data)</BLOB>
I'm looking for a way (tool?) to convert that binary data. For example, it could be that mentioned library.
Looking at the details, this is most likely Leonardo (Selex/Gematronic) Rainbow5 format. zlib is the right lib for decompression. But there are some tricks to it. A python reader is implemented in the wradlib library (https://github.com/wradlib). Maybe you can adapt from that code. Disclaimer: I'm one of the wradlib devs.
Did you try simply using the qUncompress() function? https://doc.qt.io/qt-5/qbytearray.html#qUncompress
I have .cdb files in binary format in sizes of ~630M.
I use read.cdb(file, type='cdb') from library cdb to read them in but it takes for ever to load. (20 min+)
Is this normal for a large file like this?
we are using ITEXTPDF to compress the PDF but the issues is we want to compress the files which are compressed before uploading into our site...if the files are uploaded without compressing we would like to leave those like that..
so to do that we need to identify is that PDF is compressed or not..am wondering is there any way we can identify PDF is compressed or not using ITEXTPDF or some other tool!!!..
i have tried to Google it but couldn't find appropriate answer..
kindly let me know if u have any idea...
thanks
There are several types of compression you can get in a PDF. Data for objects can be compressed and objects can be compressed into object streams.
I voted Mark's answer up because he's right: you won't get an answer if you're not more specific. I'll add my own answer with some extra information.
In PDF 1.0, a PDF file consisted of a mix of ASCII characters for the PDF syntax and binary code for objects such as images. A page stream would contain visible PDF operators and operands, for instance:
56.7 748.5 m
136.2 748.5 l
S
This code tells you that a line has to be drawn (S) between the coordinate (x = 56.7; y = 748.5) (because that's where the cursor is moved to with the m operator) and the coordinate (x = 136.2; y = 748.5) (because a path was constructed using the l operator that adds a line).
Starting with PDF 1.2, one could start using filters for such content streams (page content streams, form XObjects). In most cases, you'll discover a /Filter entry with value /FlateDecode in the stream dictionary. You'll hardly find any "modern" PDFs of which the contents aren't compressed.
Up until PDF 1.5, all indirect objects in a PDF document, as well as the cross-reference stream were stored in ASCII in a PDF file. Starting with PDF 1.5, specific types of objects can be stored in an objects stream. The cross-reference table can also be compressed into a stream. iText's PdfReader has a isNewXrefType() method to check if this is the case. Maybe that's what you're looking for. Maybe you have PDFs that need to be read by software that isn't able to read PDFs of this type, but... you're not telling us.
Maybe we're completely misinterpreting the question. Maybe you want to know if you're receiving an actual PDF or a zip file with a PDF. Or maybe you want to really data-mine the different filters used inside the PDF. In short: your question isn't very clear, and I hope this answer explains why you should clarify.
Can anybody give me a hint or initial idea how may I cut a file into chunks in Qt ? Is there any particular file like java it has built in function to split. Later on I want to calculate SHA-256 hash value of each chunks. Any idea guys ??
There is no built in function for that.
Open the original file.
Open a file for the first chunk.
Read bytes from the original file.
Write bytes to the chunk file.
Repeat.
See QFile documentation.