I am writing a 'clean-room' program that requires parsing/unparsing of jpegs. I have found all the information I need to parse/unparse baseline jpegs, but I cannot find the information that I need to parse/unparse progressive jpegs.
I need to be able to convert the compressed data to macroblocks and back, so most available frameworks are too high level. I also want to understand what is going on, hence the 'clean room' approach.
Can anybody help me please? A specification of the SOF1 header would be useful, as would be the layout of the compressed data in the scan segment.
Thanks in advance.
If you want to figure this out, I'd get this book:
https://www.amazon.com/Compressed-Image-File-Formats-JPEG/dp/0201604434/ref=sr_1_5?ie=UTF8&qid=1486949641&sr=8-5&keywords=jpeg
It explains it all in easy-to-understand terms. The author has source code at
http://colosseumbuilders.com/sourcecode/imagelib403.zip
that is designed to be easy to understand.
The SOF1 header is the same as all other SOF headers. You need to have a copy of the JPEG standard (as obtuse as it is). The other sources above will help you get through it.
Related
User needs to parse native-pdf(selectable data, not scanned, no OCR required) in local. The pdf files may be over 400 pages with large tables. Some tables may not have clear borders. Is there any API I could use?
Thanks!
Now that I know you don't want an API, I might recommend that you check out ItextSharp, from nuget. I have used this several times in the past, and there are many stack overflow forums on how to use it. https://www.nuget.org/packages/iTextSharp/5.5.13.1
EDIT: I apologize, it looks like iTextSharp has been replaced with iText 7 https://itextpdf.com/en/products/itext-7
It seems there are several PDF parser APIs out there you could use. PDFTron looks promising, and they offer a free trial: https://www.pdftron.com/pdf-sdk/parsing-library/
DocParser may also be helpful for you, https://docparser.com/features.
I found all of these through a simple google search, so it may benefit you to do some research for yourself. As we can only make broad suggestions based on the information in your question.
I want record screen (by capturing 15 screenshots per second). This part I know how to do. But I don't know how to write this to some popular video format. Best option which I found is write frames to separated PNG files and use commandline Mencoder which can convert them to many output formats. But maybe someone have another idea?
Requirements:
Must be multi-platform solutions (I'm using Free Pascal / Lazarus). Windows, Linux, MacOS
Exists some librarys for that?
Could be complex commandline application which record screen for me too, but I must have possibility to edit frames before converting whole raw data to popular video format
All materials which could give me some idea are appreciated. API, librarys, anything even in other languages than FPC (I would try rewrite it or find some equivalent)
I considered also writting frames to video RAW format and then use Mencoder (he can handle it) or other solution, but can't find any API/doc for video RAW data
Regards
Argalatyr mentioned ffmpeg already.
There are two ways that you can get that to work:
By spawning an new process. All you have to do is prepare the right input (could be a series of jpeg images for example), and the right commandline parameters. After that you just call ffmpeg.exe and wait for it to finish.
ffmpeg makes use of some dll's that do the actual work. You can use those dll's directly from within your Delphi application. It's a bit more work, because it's more low-level, but in the end it'll give you a finer control over what happens, and what you show the user while you're processing.
Here are some solutions to check out:
FFVCL Commercial. Actually looks quite good, but I was too greedy to spend money on this.
Open Source Delphi headers for FFMpeg. I've tried it, but I never managed to get it to work.
I ended up pulling the DLL wrappers from an open source karaoke program (UltraStar Deluxe). I had to remove some dependencies, but in the end it worked like a charm. The relevant (pascal) code can be found here:
http://ultrastardx.svn.sourceforge.net/viewvc/ultrastardx/trunk/src/lib/ffmpeg-0.10/
There was some earlier discussion with a Delphi component here. It's a very simple component that sometimes generates some weird movies. Maybe a start.
How can I write a script or program to manipulate Adobe Photoshop files? I'd like to be able to do something like read a Adobe PSD file, rename the layers, and save it back to a PSD format.
The files look to be saved with a combination of XML and serialized data. I looked at the file's code and see that it has <x:xmpmeta near the start, did some google searching to find the wikipedia article about xmp - Extensible Metadata Platform, but I'm unclear if that is the format for the entire file or just for the metadata portion.
I saw that there is a PSD parser class for PHP available, and not a bad article about how to use it, although it seems like it is just for reading / converting and not for writing / saving.
But I'd like to know:
What format are these files stored in?
Where are the guidelines for interfacing with that format?
Are there some classes / tools available for manipulating that file format? Any language would be fine for a start.
I'm happy to do more research on my own but I'm hoping for some guidance to know what I should be looking for.
I'm not familiar with it myself, but there is an official SDK for Photoshop available that should let you do all that and more with .psd files.
There are not so many options. The general advice would be to look into buying Adobe InDesign Server. In some cases it can be cost prohibitive and you might be interested in 3-party SDKs. Unfortunately there are a few options in the market. One of them is Graphics Mill image processing SDK (http://www.graphicsmill.com/photoshop-psd).
Disclaimer: I work for Aurigma which runs Graphics Mill project.
just wanted some help on ePub specifications.. Is it mandatory for the toc.ncx to have the src(ie. the xhtml) .I have observed the same content src is also available in the .opf file.
Yes, that is mandatory and that's a design problem :
Overlap between NCX and OPF metadata
Because the NCX is borrowed from another standard, there is some
overlap between the information encoded in the NCX and that in the
OPF. This is rarely a problem when you generate EPUBs
programmatically, where the same code can output to two different
files. Take care to put the same information in both places, as
different EPUB readers might use the values from one or the other.
Source
That's not the case anymore in the future version of the norm (ePub 3), but please note that no device support it currently.
I have a site where a user can upload a photo. I have no idea how to handle photos. To make a thumbnail out of a large res photo, do I just resize the width and the height? Or is there a better way to do this?
If you could point me to any resources or give me any tips, that would be great.
I'm using Ruby on Rails, if that matters. I don't really want gems for this because I want to learn how to do it myself.
For some of this, "learning how to do it yourself" is going to be a significant undertaking. Resizing the image, for example. Go ahead and find an open source library (such as a gem) that resizes images and look through its source code. It's not impossible to do on your own, but a lot of that sort of thing is built on the expertise that's come before, etc. There's nothing wrong with making use of a tool somebody else has created, provided that you understand what the tool is doing.
A few points to hopefully help you out:
Go with a white-list approach of which image formats you support. Don't just let users upload anything that they call an image.
Each format you support is going to have its own standards (possibly multiple) for meta-data. Stripping out that data wholesale may or may not be a good idea. For example, a jpeg may contain its orientation in its EXIF data and if you strip that out you may be effectively rotating the image. Certain fields, such as geotagging, you may want to strip out in the effort to protect your users' privacy, etc. Again, look into existing libraries for this and see how they do it.
DO NOT implicitly trust the file name extension for determining the type of the image. It's possible for a user to construct a malicious file that isn't really an image, pass it off as an image to an unsuspecting host, and effectively open a security flaw on that host as it tries to process the file as an image. There was a question about determining file type in Ruby here, and I'm sure there's a lot more to be found on the subject.
David answered the question well, but I thought I might be able to provide some more specific information regarding your question.
Use the Paperclip gem, combined with RMagick, an ImageMagick wrapper for Ruby. You can set post-processing options and create multiple resizings.
If you really want to do it yourself, checkout the actual gem at https://github.com/thoughtbot/paperclip and you'll see how that author does it. Part of the thought behind Ruby on Rails is DRTW (Don't Reinvent the Wheel). Utilize what's out there and build on it. It will save you time, and enable you to do more in the longrun.
An alternative is to use a third party service such as http://resizer.co (I am not affiliated)
Replace a URL to an image from your site, say:
http://example.com/images/abc123.jpg
with the following (for a 200 x 200 image)
http://www.resizer.co?image=http://example.com/images/abc123.jpg&w=200&h=200
You may run into issues with distortion and the 'aspect ratio' not being maintained, but it could be a good start.