Let’s assume that you are developing an Android version of
the already existing .NET application (desktop or web).And this application
processes PDF files and saves them as images somewhere.
I would personally look for a cross –platform solution that
would reduce the amount of code I’d have to rewrite in order to target all these
platforms.
One of
the solutions that could be easily found is to use Xamarin
- a great project based on Mono and now becoming very popular for writing apps
working on iOS, Mac, Windows and Android.
That’s
the base part, but I also need a library that works fine with Xamarin and can
do PDF to image conversion. In my previous post Creatingcross-platform PDF viewer using GTK# I demonstrated how we can create a
simple application that shows PDF content on Windows and Mac OS X , and now it’s
Android app’s turn.
So let’s follow step-by-step approach taken in previous posts
and get this working.
STEP I - Setup
Refer
to the post Creatingcross-platform PDF viewer using GTK#
on how to setup environment, download latest Apitron PDF Rasterizer for
.NET package and unzip it to the desired location.
STEP II – Getting things built
To make
things simpler we provide a sample project called AndroidSample that can be
found in Samples folder inside the
downloaded package. Open it using desired IDE, I will use MS VS.
If everything is set up correctly
project opens fine and builds without errors. If build fails, make sure that
correct component dll is referenced. Remove the old reference and add new one,
navigating to [Package_Folder]\ Microsoft.NET
v2.0Android\Apitron.PDF.Rasterizer.dll.
Otherwise
it might be something wrong with environment setup, please read Xamarin
documentation or post a comment here, I’ll try to help.
STEP III - Playground
Ok, you’ve
got it compiled! And now to make it more interesting, let’s not use the default
PDF file provided with the sample (you may still use it, no problem, just hit
Run). I’m going to add a new file, from
Adobe samples - http://acroeng.adobe.com/Test_Files/viewing/3BigPreview.pdf.
For
those decided to go this way, download the file by the link above and put in
into Assets directory of the project, don’t forget to include it in project with AndroidAsset
build action. Also navigate to MainActivity.cs and change button_click handler, replacing
“testfile.pdf” to “3bigpreview.pdf”.
Build and hit Run, you should see the similar screen as
below:
I used physical device connected to the PC, but you may want to run
it on emulator also, to do it - click Start
emulator image and run desired emulator.
So click OK and application deployment begins… once it’s finished,
the application starts:
You see that application has very simple UI layout with just
one button that says “Click me to start
rendering”, let’s click it and see what happens.
Application starts processing the file that we have placed
into its Assets folder, and when it
finishes the following screen appears:
Done!
THE CODE
Here is the actual code that renders and saves image to
storage, it is located in MainActivity.cs
// load the linked sample pdf file
using (Stream stream =
Assets.Open("3bigpreview.pdf"), ms
= new MemoryStream())
{
stream.CopyTo(ms);
ms.Position = 0;
// create focument from the stream and request first page
Document doc = new
Document(ms);
Page page = doc.Pages[0];
// render the page using default settings
int[] bitmapData = page.RenderAsInts((int)page.Width, (int)page.Height,
new RenderingSettings());
// convert given data to an android bitmap
Bitmap bm
= Bitmap.CreateBitmap(bitmapData, (int)page.Width, (int)page.Height,
Bitmap.Config.Argb8888);
// save image to device's gallery
string
imageUri = MediaStore.Images.Media.InsertImage(this.ContentResolver, bm, "MyImage",
"An image created using
Apitron.PDF.Rasterizer");
// try to open the newly created image
StartActivity( new
Intent( Intent.ActionView, Android.Net.Uri.Parse(imageUri))
);
}
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