Retrieve text from pdf in iOS, using zachron iphonepdf? - ios

I'm using the same zachrone iphonepdf but I did not get the text. My text view shows nothing. What's the problem?
Here is my code:
NSString *text=convertPDF(#"Course.pdf");
texview.text=text;
But I did not get anything in text view?

The text extractor zachron / pdfiphone (I assume you meant that one) is extremely naive and makes very many assumptions.
It ignores the PDF file structure and, therefore completely ignores whether the data it inspects is still used in the current revision.
It ignores encryption and therefore will fail completely for many documents with usage restrictions.
It completely ignores font encodings and implicitely assumes an ASCII'ish one --- this is fairly often true in small PDFs with English text only and not embedded fonts; otherwise the result can be anything.
... many many more assumptions ...
Unless one only has to deal with very simple documents and the extracted text is not really necessary for the functionality of one's code, I would propose using different code for text extraction.

Related

Eggplant : How to read text with special characters like ' _ etc

I am trying to read a text in a given rectangle using readText() function.
The function works correctly except when it has to read some text which has special characters like ' _ & etc.
I tried using validCharacters with readText() function. But it didn't help.
Code -
put ReadText((287,125,810,164),validCharacters:"_-'.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890") into Login
I tried working with character collections. But that doesn't seem to be right because the text trying to pick is a dynamic text combination of numbers alphabets and a special character. So one cannot create a library of character collection of every alphabet (a-z, A-Z), numbers(0-9) and special characters.
Example of text trying to read:
Login_Userid1_1, Login'Userid1_1
So how do I read such text correctly
Debugging OCR is a bit of an imprecise science. EggPlant has a lot of OCR Parameters to tweak. When designing test cases it's best to try use other mechanisms to gather information whenever possible. ReadText() should be considered a last resort when more reliable methods are unavailable. When I've used it I've often needed to do a lot of trial and error to find the right set of settings, and SearchRectangle to get consistent results. Without seeing exactly what images you are trying to read text from it's difficult to impossible to troubleshoot where the issue might be.
One thing that does stand out to me is that you're trying to read strings that may contain underscores. ReadText() has an optional property IgnoreUnderscores which treats underscores as spaces. By default this property is set to ON. It defaults to ON because some OCR engines have problems identifying underscore characters consistently.
If you want to have ReadText() handle underscores you'll want to explicitly set this property to OFF.
ReadText(rect, validCharacters:chars, ignoreUnderscores:OFF)

How to properly do custom markdown markup

I currently work on a personal writing project which has ended up with me maintaining a few different versions due to the differences of the relevant platforms and output formats I want to support that are not trivially solved. After several instances of me glancing at pandoc and the sheer forest that it represents, I have concluded mere templates don't do what I need, and worse, that I seem to need a combination of a custom filter and writer... suffice to say: messing with the AST is where I feel way out of my depth. Enough so that, rather than asking specific questions of 'how do I do X' here, this is a question of 'is X the right way to go about it, or what is the proper way to do it, and can you give an example of how it ties together?'... so if this question is rather lengthy: my apologies.
My current goal is to have custom markup like the following which is supposed to 'track' which character says something:
<paul|"Hi there">
If I convert to HTML, I'd want something similar to:
<span class="speech paul">"Hi there"</span>
to pop out (and perhaps the <p> tags), whereas if it is just pure markdown / plain text, I'd want it to silently disappear:
"Hi there"
Looking at the JSON AST structures I've studied, it would make sense that I'd want a new structure type similar to the 'Emph' tag called 'Speech' which allows whole blobs of text to be put inside of it with a bit of extra information attached (the person speaking). So something like this:
{"t":"Speech","speaker":"paul","c":[ ... ] }
Problem #1: At the point a lua-filter sees the document, it is obviously already distilled to an AST. This means replacing the items in a manner similar to what most macro expander samples do cannot really work since it would require reading forward. With this method, I just replace bits and pieces in place (<NAME| becomes a StartSpeech and the first solitary > that follows becomes an EndSpeech, but that would make malformed input a bigger potential problem because of silent-ish failures. Additionally, these tags would be completely out of sorts with how an AST is supposed to look.
To complicate matters even further, some of my characters end up learning a secondary language throughout the story, for which I apply a different format that contains a simplified understanding of the spoken text with perspective-characters understanding of what was said. Example:
<paul|"Heb je goed geslapen?"|"Did you ?????">
I could probably add a third 'UnderstoodSpeech' group to my filter, but (problem #2) at this point, the relationship between the speaker, the original speech, and the understood translation is completely gone. As long as the final documents need these values in these respective orders and only in these orders, it is fine... but what if I want my HTML version to look like
"Did you?????"
with a tool-tip / hover-over effect containing the original speech? That would be near impossible to achieve because the AST does not contain that kind of relational detail.
Whatever kind of AST I create in the filter is what I need to understand in my custom writer. Ideally, I want to re-use as much stock functionality of pandoc as possible for the writer, but I don't even know if that is feasible at this point.
So now my question: could someone with great pandoc understanding please give me an example on how to keep relevant data-bits together and apply them in the correct manner? By this I mean show a basic example of what needs to be put in the lua-filter and lua-writer scripts in the following toolchain
[CUSTOMIZED MARKDOWN INPUT] -> lua-filter -> lua-writer -> [CUSTOMIZED HTML5 OUTPUT]

Max size for PO file strings

I know that PO / MO files are meant to be used for small strings like button names, labels, etc. Not long text like an About page, etc.
But lately I am encountering a lot of situations that are in the middle. For example, a two sentence call to action. Or a short paragraph.
Is there best practice or "rule of thumb" for when a string is too long to put in a PO file?
update
For "long" text I use partials and include the correct language version. My question is WHEN is it optimal to use one vs the other. I've heard that PO files are "inefficient" for "long" pieces of text. But what does that mean and when is it too "long"? Or is this not a concern?
Use one entry for a self-contained chunk of text; e.g. a sentence as you say.
Two sentences that belong together and don't make sense without each other should be one entry. Why? Because otherwise the translator wouldn't have the context necessary to translate it well. Same goes for a short paragraph, e.g. explaining a setting: if it's inseparable in the code, it should be one entry.
If you encounter a situation where you have lots of long texts regularly (e.g. entire pages or paragraphs of pages), that's usually a sign that you are using an ill-fitting tool. Some people do it, using Gettext for entire articles, but you're better off having separate documents in such cases. But that doesn't seem to be the case here.

Auto page break in libHaru PDF

I'd like to add an automatic page break to a libHaru PDF in iOS.
I do have several text fields in the app which contain the user filled data. when i generate the pdf i first measure the expected size of the text-rect going to be created. if it exceeds the remaining space i trigger a hpdf_new_page event and put the text on an new page. i'd like to have this just in part automatically. so if the text exceeds the space on the current page it should split and continue on a new page without me checking or doing anything.
unfortunately i can't find anything like this in the documentation.
Line counting using fgets() may help. When your print program opens a file to print, each line can be copied to the pdf file and checked for a form feed character
or
if the line count has reached a limit.
Another possible solution is to use a character count limit with "while(getc(file) != EOF)".
This link uses libharu to print basic text files with PCL commands to change the font.
https://github.com/DaDaDadeo/GetCycle/blob/master/pcl_to_pdf.c
The form feed character '\f' (ascii 12) and 61 lines will trigger a new page. There are other conditions in the program to restrict a new page but the general idea is illustrated.
The results are the same as a printer using telnet raw 9100 protocol. The pcl commands are limited to just a couple of font changes so it is not too complicated.
Libharu is rather low-level library, and I could not even expect of appearing such automatic page splitting in newer versions due to number of reasons. Hereafter I state two of them:
There is no good, preferred strategy how to place remaining of non-fitting text on the next page. In some cases it could be even impossible at all.
There is no good, preferred strategy for text splitting.
Why?
Consider your font is extremely large, and just one letter (for instance, wide one as "W") does not fit into the page. Where we are supposed to place it? On the next page? Ok, we add new page... oops, it does not fit this page too - as soon as all our pages have the same size. Dead-end without any good, straightforward way out.
In other words, there should be a user-defined strategy for these cases. Almosy every naive implementation will have such a corner cases.
libharu does not know where it should split your text automatically. It does not know hyphenation rules of your language, it does not know whether it should respect spaces or not (wrap whole words only or not), and so on. It's up to you to specify these rules.
So, you should call HPDF_Font_MeasureText for some part of your text string, decide if it fits into your page (excluding margins, footers - which also out of libharu's internal knowledge) and render it. And note that there is no simple formula for text size depending on its length. String "wwww" is more than twice wider than "iiii", of course if your font is not mono-spaced.

Fast Search to see if a String Exists in Large Files with Delphi

I have a FindFile routine in my program which will list files, but if the "Containing Text" field is filled in, then it should only list files containing that text.
If the "Containing Text" field is entered, then I search each file found for the text. My current method of doing that is:
var
FileContents: TStringlist;
begin
FileContents.LoadFromFile(Filepath);
if Pos(TextToFind, FileContents.Text) = 0 then
Found := false
else
Found := true;
The above code is simple, and it generally works okay. But it has two problems:
It fails for very large files (e.g. 300 MB)
I feel it could be faster. It isn't bad, but why wait 10 minutes searching through 1000 files, if there might be a simple way to speed it up a bit?
I need this to work for Delphi 2009 and to search text files that may or may not be Unicode. It only needs to work for text files.
So how can I speed this search up and also make it work for very large files?
Bonus: I would also want to allow an "ignore case" option. That's a tougher one to make efficient. Any ideas?
Solution:
Well, mghie pointed out my earlier question How Can I Efficiently Read The First Few Lines of Many Files in Delphi, and as I answered, it was different and didn't provide the solution.
But he got me thinking that I had done this before and I had. I built a block reading routine for large files that breaks it into 32 MB blocks. I use that to read the input file of my program which can be huge. The routine works fine and fast. So step one is to do the same for these files I am looking through.
So now the question was how to efficiently search within those blocks. Well I did have a previous question on that topic: Is There An Efficient Whole Word Search Function in Delphi? and RRUZ pointed out the SearchBuf routine to me.
That solves the "bonus" as well, because SearchBuf has options which include Whole Word Search (the answer to that question) and MatchCase/noMatchCase (the answer to the bonus).
So I'm off and running. Thanks once again SO community.
The best approach here is probably to use memory mapped files.
First you need a file handle, use the CreateFile windows API function for that.
Then pass that to CreateFileMapping to get a file mapping handle. Finally use MapViewOfFile to map the file into memory.
To handle large files, MapViewOfFile is able to map only a certain range into memory, so you can e.g. map the first 32MB, then use UnmapViewOfFile to unmap it followed by a MapViewOfFile for the next 32MB and so on. (EDIT: as was pointed out below, make sure that the blocks you map this way overlap by a multiple of 4kb, and at least as much as the length of the text you are searching for, so that you are not overlooking any text which might be split at the block boundary)
To do the actual searching once the (part of) the file is mapped into memory, you can make a copy of the source for StrPosLen from SysUtils.pas (it's unfortunately defined in the implementation section only and not exposed in the interface). Leave one copy as is and make another copy, replacing Wide with Ansi every time. Also, if you want to be able to search in binary files which might contain embedded #0's, you can remove the (Str1[I] <> #0) and part.
Either find a way to identify if a file is ANSI or Unicode, or simply call both the Ansi and Unicode version on each mapped part of the file.
Once you are done with each file, make sure to call CloseHandle first on the file mapping handle and then on the file handling. (And don't forget to call UnmapViewOfFile first).
EDIT:
A big advantage of using memory mapped files instead of using e.g. a TFileStream to read the file into memory in blocks is that the bytes will only end up in memory once.
Normally, on file access, first Windows reads the bytes into the OS file cache. Then copies them from there into the application memory.
If you use memory mapped files, the OS can directly map the physical pages from the OS file cache into the address space of the application without making another copy (reducing the time needed for making the copy and halfing memory usage).
Bonus Answer: By calling StrLIComp instead of StrLComp you can do a case insensitive search.
If you are looking for text string searches, look for the Boyer-Moore search algorithm. It uses memory mapped files and a really fast search engine. The is some delphi units around that contain implementations of this algorithm.
To give you an idea of the speed - i currently search through 10-20MB files and it takes in the order of milliseconds.
Oh just read that it might be unicode - not sure if it supports that - but definately look down this path.
This is a problem connected with your previous question How Can I Efficiently Read The First Few Lines of Many Files in Delphi, and the same answers apply. If you don't read the files completely but in blocks then large files won't pose a problem. There's also a big speed-up to be had for files containing the text, in that you should cancel the search upon the first match. Currently you read the whole files even when the text to be found is in the first few lines.
May I suggest a component ? If yes I would recommend ATStreamSearch.
It handles ANSI and UNICODE (and even EBCDIC and Korean and more).
Or the class TUTBMSearch from the JclUnicode (Jedi-jcl). It was mainly written by Mike Lischke (VirtualTreeview). It uses a tuned Boyer-Moore algo that ensure speed. The bad point in your case, is that is fully works in unicode (widestrings) so the trans-typing from String to Widestring risk to be penalizing.
It depends on what kind of data yre you going to search with it, in order for you to achieve a real efficient results you will need to let your programm parse the interesting directories including all files in there, and keep the data in a database which you can access each time for a specific word in a specific list of files which can be generated up to the searching path. A Database statement can provide you results in milliseconds.
The Issue is that you will have to let it run and parse all files after the installation, which may take even more than 1 hour up to the amount of data you wish to parse.
This Database should be updated eachtime your programm starts, this can be done by comparing the MD5-Value of each file if it was changed, so you dont have to parse all your files each time.
If this way of working can be interesting if you have all your data in a constant place and you analyse data in the same files more than each time totally new files, some code analyser work like this and they are real efficient. So you invest some time on parsing and saving intresting data and you can jump to the exact place where a searching word appears and provide a list of all places it appears on in a very short time.
If the files are to be searched multiple times, it could be a good idea to use a word index.
This is called "Full Text Search".
It will be slower the first time (text must be parsed and indexes must be created), but any future search will be immediate: in short, it will use only the indexes, and not read all text again.
You have the exact parser you need in The Delphi Magazine Issue 78, February 2002:
"Algorithms Alfresco: Ask A Thousand Times
Julian Bucknall discusses word indexing and document searches: if you want to know how Google works its magic this is the page to turn to."
There are several FTS implementation for Delphi:
Rubicon
Mutis
ColiGet
Google is your friend..
I'd like to add that most DB have an embedded FTS engine. SQLite3 even has a very small but efficient implementation, with page ranking and such.
We provide direct access from Delphi, with ORM classes, to this Full Text Search engine, named FTS3/FTS4.

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