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Not sure if this is the right place for this question but i wasn't able to find any other medium of advise.
Text extraction. As mkl mentioned in comments, PDF may already contain a layer of text (digitally created or pre-OCRed), or it may be image-only PDF without text (scanned or rasterized). Existing text extraction can be attempted, but I give it low chance of success because PDF does not have coordinate information for text extraction purposes. In other words, it is very easy to programatically extract ALL existing text from within a PDF, but it is hard to extract text from a specific zone or region. For this reason, OCR is frequently used even if text already exists inside, because OCR returns text with very detailed location and region information, which can be mapped to the image coordinates.
PDF zone highlighting. I believe you will either have to re-build a new PDF with certain area highlighted, or build your own PDF-like viewer that will merry image and coordinates and text and highlighted area. I would go for the second option of creating your own viewer because you have extra controls over functionality and UI. Your viewer could take PDF as input and produce modified PDF as output, but as you work with the document it does not have to be a PDF, even though it could behave like PDF to the user's perspective, but with added functionality for interaction.
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I am doing a simple app where I take a picture, fill some text from the UI and store the image + text together.
Eventually the user can select the picture from a recyclerview and edit the associated text (or delete the whole image + text group).
I have no hint on what kind of data structure should be used.
I heard that SQL lite should be used for such tasks - since the text data could change according to the user actions, but I think that using tables (one or more) for the purpose of storing images and text could be overkill - also because I don't expect to have a lot of images in my app.
I'm wondering if any other data structure is available for this purpose (similar to C strctures, or python dictionaries).
Also, any kind of hint about keyword to search for this topic or resource would be really appreciated.
Just for the sake of discussion, I am developing using kotlin.
For storing images, you should store them as files, and store file paths of those images in the database with text. Moreover, when you read it back you can use Picasso or Glide to load those image paths into ImageView.
Also, if you want to store images in external storage, make you request runtime-permission and add permission to the manifest file.
However, if you store files in internal storage, you don't need to request permission.
Learn more about Runtime-Permission and Storage in Android.
I would suggest use Room for working with SQLite in Android.
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I am sorry to post this question but I need some guidance for a project in MATLAB.
Is there any way via an Android App to take a image that can characterize the chemical components of water computationally?
I have to find the presence of Arsenic in water remotely. The lab attended would just take an image of the water - all he can do is send it remotely to me.
How using Image processing or rather what technology I can make use that I can detect chemical composition of the water as in the image?
First, you have to remember that StackOverflow is all about software issues (not about any particular application).
Regarding your question: I am afraid you cannot do it straighforward. First, given a RGB image like this one:
.
Could you tell me if the water contains arsenic or if the color is due to the mud? You cannot say that the water contains arsenic, so you cannot develop an application to perform this task.
You have two posibilities:
Use an spectrometer. But it is complicated to use it remotely.
Use some chemical tint to change the color of the image if it contains arsenic.
Now, the software aspect:
In the question title you talked about Matlab, but then you ask about Android... I am confused. Could you clarify that particular point?
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Okay, this is the first time I'm handling pdf in android.
What I have:
Editable PDF File with 2 pages (Forms to be exact, with brackets to tick, fields to comment etc.)
What I need to do:
Store the PDF some where is the sd card (so that users do not need to download from any server)
Allow users to open & edit the form
Save the contents that was edited into SQLite
Problem now is that I do not know how to open the PDF file within my application & how to allow users to edit the files. I did see through this : Reading PDF from within an Android application
However, I do not know how to allow users to edit the PDF File. Would anyone please guide me? Thanks so much!
It is open source and built for unix/debian Linux so it will require some toying with, but it is a start.
http://pdfedit.cz/en/index.html
you can use SDKs like Foxit here..
and another way is libraries like Qoppa pdf or MuPdf are free
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I wanted to open internal anchors and embedded hyperlink from pdf viewer application. What would the suggested way to implement this functionality. As I can right now read pdf successfully.
MuPDF reader is not supporting interactive feature. But you can do one thing, you can create separate each PDF wise text file, in that you can mention x,y co-ordinates of interactive area.
And you can map that area in PDF pagewise image, and make that part interactive. Hope you do understand.
Simply you need to have Adobe Acrobat Reader.
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In my application I am downloading pdf file from the net. Is it possible in Android to convert that pdf file into text (String or character)?
Actually, it is possible to convert PDF to text. A better term than convert would be extract though.
You only need an OCR tool if the PDF has images only. This is typically the case if the PDF is a result of scanning documents. But even then, text is often inserted by the scan driver as invisible text so that the PDF content can be searched.
Bruno Lowagie (Developer of iText) says unfortunately no.
That's very normal. It's 'in the nature' of PDF.
PDF is a one-way process. The PDF is the end product.
You are not supposed to convert it to text.
You need an OCR tool.
http://itext-general.2136553.n4.nabble.com/Convert-PDF-to-text-td2142916.html
Regards Stefan