B4A Library OCR - Extracting text from a bitmap using the Play Services Vision API

This request comes from here:
https://www.b4x.com/android/forum/threads/ocr-offline-on-screen.84867/#post-538774

The attached project extracts text from a bitmap that you can pass to the library making use of the Android Vision API.

Sample code:
B4X:
#Region  Project Attributes
    #ApplicationLabel: b4aMobileVisionBitmap
    #VersionCode: 1
    #VersionName:
    'SupportedOrientations possible values: unspecified, landscape or portrait.
    #SupportedOrientations: portrait
    #CanInstallToExternalStorage: False
#End Region


#Region  Activity Attributes
    #FullScreen: False
    #IncludeTitle: True
#End Region

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'These variables can be accessed from all modules.

End Sub

Sub Globals
    'These global variables will be redeclared each time the activity is created.
    'These variables can only be accessed from this module.
 
    Dim mvbm As MobileVisionBitmap

    Private Button1 As Button
    Private iv1 As ImageView
    Private bm As Bitmap
End Sub

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    Activity.LoadLayout("main")
    bm.Initialize(File.DirAssets,"saying1.png")   'saying.png and saying1.png are in the /Files folder of the B4A project
    iv1.Bitmap = bm
 
    mvbm.Initialize("mvbm")

End Sub

Sub Activity_Resume

End Sub

Sub Activity_Pause (UserClosed As Boolean)

End Sub


Sub Button1_Click
 
    mvbm.decodeBitmap(bm) 
    bm = Null
    bm.Initialize(File.DirAssets,"saying1.png")   'saying.png and saying1.png are in the /Files folder of the B4A project
    iv1.Bitmap = bm
 
End Sub

Sub mvbm_blocks_result(blocks As String)
 
    Log("B4A Blocks = " & blocks)
 
End Sub

Sub mvbm_lines_result(lines As String)
 
    Log("B4A Lines = " & lines)
 
End Sub

Sub mvbm_words_result(words As String)
 
    Log("B4A Words = " & words)
 
End Sub

Sub mvbm_error_result(error As String)
 
    Log("B4A ERROR = " & error)
 
End Sub

Take note of the B4A manifest file:
B4X:
'This code will be applied to the manifest file during compilation.
'You do not need to modify it in most cases.
'See this link for for more information: https://www.b4x.com/forum/showthread.php?p=78136
AddManifestText(
<uses-sdk android:minSdkVersion="5" android:targetSdkVersion="22"/>
<supports-screens android:largeScreens="true"
    android:normalScreens="true"
    android:smallScreens="true"
    android:anyDensity="true"/>)
SetApplicationAttribute(android:icon, "@drawable/icon")
SetApplicationAttribute(android:label, "$LABEL$")
'End of default text.

AddApplicationText(<meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />
        <meta-data
            android:name="com.google.android.gms.vision.DEPENDENCIES"
            android:value="ocr" />)

If you don't have the Android Vision dependencies installed then you will need an initial internet connection for the dependencies to be installed. After that an internet connection will not be required.

This is version 1.00. It will expire on 31 October 2017.


Bitmap loaded into the imageview.
1.png



B4A Log when clicking on button Read Text
2.png
 

Attachments

  • MobileVisionBitmap.xml
    1.2 KB · Views: 653
  • MobileVisionBitmap.jar
    10 KB · Views: 697
  • b4aMobileVisionBitmap.zip
    130 KB · Views: 741
Last edited:

Sandman

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if a dev not doing this then the number of donations one can expect are near null

Aha, that makes it easier to understand. And I kind of suspect that in full it means "This is a time-limited version that will expire on 31 October 2017. If you want the version without that limitation, you should buy it by giving me a donation and I'll send you the file."

I suspect that most of the regulars and all of the seniors here in the forum understood Johan's meaning without problems. But I still consider myself a beginner and a rookie here, and to me it wasn't really clear at all. (I'm not trying to pick a fight or act stupid or anything, I was genuinely confused by the time-limit.)

And for the record I think it absolutely is fair to be paid for ones efforts.
 

Johan Schoeman

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I do agree that it is better to (somehow) allow for a 30 day trial period (or something like that), but that is technically more complicated to realize.

PS
Today I tested the Camera versus the Bitmap version to perform OCR on a TV subtitle (to make a speaking subtitle reader for blind users). At first I thought the camera performed better, but after more experimentation there appears to be no difference: The results vary between excellent, good and poor. If parts of a subtitle have a bright background then that part of the text gets distorted with the OCR. I am still looking for ways to enhance a bitmap (not easy) to make the (white) text more pronounced.
Syd, it seems to be rather complicated to extract text from some images especially so if the color of the text vs that of the background color are close to one another. I guess the only way to try and do it successfully is to greyscale the image (there are numerous different ways to do it - I have posted a sample project here https://www.b4x.com/android/forum/t...-of-converting-rgb-images-to-grayscale.44316/ ), determine the OTSU threshold of the greyscaled image (see this project https://www.b4x.com/android/forum/threads/otsu-thresholding-binarization-of-images.44406/), and then to binarize the greyscaled image from where one can then try to extract the text. I have tried to do it this way with mixed results - from excellent to good to poor to nothing. I have however not tried to extract the text from a greyscaled image only - just from a binarized image. But I guess we can expect similar results when passing a greyscaled image or binarized imaged to the lib - Excellent, good, poor, nothing....

When time permits I will look into the lib again to try and understand what the original author did and then see if we can somehow improve the OCR.
 
Last edited:

peacemaker

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The lib "cannot start as expired".

Can trial be updated ?
I'd like to check working, as found that the Vision libs cannot be initialized, app is stopped on my f...ng Samsung Android 7.
 
Last edited:

ThRuST

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This is the weakness and backside with small 3rd party solutions that cost money. As time goes by the developer might not even be around or reached to update his product range. It would be better to make all source code publically available because of this fact. Why else should the library post still reside on a public forum for developers?
 

Johan Schoeman

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This is the weakness and backside with small 3rd party solutions that cost money. As time goes by the developer might not even be around or reached to update his product range. It would be better to make all source code publically available because of this fact. Why else should the library post still reside on a public forum for developers?
I will post the Java code for you and you can then change it to your liking, recompile it, post the new lib files in this thread. Will do so tomorrow.
 

ThRuST

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If you don't have the Android Vision dependencies installed then you will need an initial internet connection for the dependencies to be installed. After that an internet connection will not be required. This is version 1.00. It will expire on 31 October 2017.

Thanks for updating your library so initialization is possible. Even though there's other solutions since your previous update is getting old. Cheers :)
 

Johan Schoeman

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Thanks for updating your library so initialization is possible. Even though there's other solutions since your previous update is getting old. Cheers :)
Here it the source code - change it to your liking.
 

Attachments

  • src.zip
    2.5 KB · Views: 457

ThRuST

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Thanks, but that's not really needed since I found another solution. Hopefully your solution can help someone else. In general source code updates should always be posted in the first post to prevent library updates to be scattered allover the place. Erel might have told you this as well allready.
 

Johan Schoeman

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Thanks, but that's not really needed since I found another solution. Hopefully your solution can help someone else. In general source code updates should always be posted in the first post to prevent library updates to be scattered allover the place. Erel might have told you this as well allready.
Use from the forum whatever works for you. There are probably many other solutions on the forum that will solve your requirements.
 

ThRuST

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Well since you're still updating your library all is good and well. With a new expiration date your library is a great contribution :)
 

Johan Schoeman

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Well since you're still updating your library all is good and well. With a new expiration date your library is a great contribution :)
There is no expiration date in the Java code that I have posted....You just need to compile it into a library (Jar and Xml)
 

ThRuST

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Sometimes it helps to keep shouting. No more limit in the initialization guys. yiihaa :)
 
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