B4J Question Writing array of ints to image file...

[rbghongade]

Dear friends,
I want to write the processed data (array of ints) as an output image file,but am not quite getting it. Tried to use writetostream method but am not being successful.

 

[sorex]

Dim out As OutputStream = File.OpenOutput(file.dirapp,"image.png", False)
mycanvas.Snapshot.WriteToStream(out)
out.Close

 

[rbghongade]

Dear sorex,
That is wonderful. Thanks. But is there no way to avoid drawing on the canvas but directly saving to the output image?

 

[Erel]

You can use ByteConverter to convert the array of ints to an array of bytes and then write the bytes: https://www.b4x.com/android/forum/threads/70111/#content

 

[rbghongade]

Dear Erel,
My image data is 2D array of ints and the example requires 1D array of bytes, how to do that?

 

[Erel]

Use RAF.WriteInt to write each of the values. Or create a large 1d array of ints and "flatten" the 2d array. The second option will be faster.

 

[rbghongade]

Dear Erel,
I flattened the 2D array to 1D array, converted it using Byteconverter but if I try to use the sub BytesToImage(bytes() As Byte) As Image to get an image and then use the WriteToStream method it flags an error as shown below:

main._appstart (java line: 117)
java.lang.IllegalArgumentException: image == null!
    at javax.imageio.IIOImage.<init>(IIOImage.java:109)
    at anywheresoftware.b4j.objects.ImageViewWrapper$ImageWrapper.WriteToStream(ImageViewWrapper.java:182)
    at b4j.example.main._appstart(main.java:117)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:90)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:77)
    at b4j.example.main.start(main.java:38)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)

 

[sorex]

I thinks it's better to show some code aswell.

 

[rbghongade]

I thinks it's better to show some code aswell.

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Dim imat(512,512) As Int
    Dim inew(512,512) As Int
    Dim new(512*512) As Int
    Dim img,imgnew As Image
    Private btnQuit As Button
    Private ImageView1 As ImageView
    Private Pane1 As Pane
    Dim bc As ByteConverter
    Dim mycanvas As Canvas
    Dim k As Int
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("1") 'Load the layout file.
    MainForm.Show
    img.Initialize(File.DirApp, "lena_gray.bmp")
    'bc.LittleEndian = True
    For i=0 To 511
        For  j=0 To 511
            Dim p As Int=ToUnsigned(img.GetPixel(i,j))
            imat(i,j)=p
            If p>=127 Then
            inew(i,j)=1
               
            Else
            inew(i,j)=0
               
            End If
            new(k)=inew(i,j)
            k=k+1
           
        Next
    Next

    imgnew=BytesToImage(bc.IntsToBytes(new))
    Log(new.Length)
    Dim out As OutputStream = File.OpenOutput(File.dirapp,"image.bmp", False)
    imgnew.WriteToStream(out)
    out.Close
    ImageView1.SetImage(img)
   
End Sub

Sub ToUnsigned(b As Byte) As Int
    Return Bit.And(0xFF, b)
End Sub
'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

Public Sub ImageToBytes(I As Image)
    Dim Out As OutputStream = File.OpenOutput(File.DirApp, "1.bmp",True)
   
    Out.InitializeToBytesArray(0)
    I.WriteToStream(Out)
    Out.Close
    Return
End Sub

Public Sub BytesToImage(bytes() As Byte) As Image
    Dim In As InputStream
    In.InitializeFromBytesArray(bytes, 0, bytes.Length)
    Dim bmp As Image
    bmp.Initialize2(In)
    Return bmp
End Sub

Sub btnQuit_Click
    MainForm.Close
End Sub

 

[Erel]

You should use BytesToFile if you want to write an array of bytes to a file.

 

[rbghongade]

Tried using BytesToFiles but it creates the a file with zero bytes.(empty)

 

[Erel]

The problem is not in BytesToFiles. It will save the data correctly.

 

[rbghongade]

Dear Erel,
During debug, the flattened array(1D array) shows only 1000 values , but the actual size is 262144, is this ok? I must be doing something wrong as I am still unable to write data to the file.
Also can you wrap the java image processing library (example;https://github.com/imglib/imglib2) or similar which takes care of image I/O and formats? That would be a great thing ! I hope I am not asking too much!
regards,

 

[Erel]

During debug, the flattened array(1D array) shows only 1000 values , but the actual size is 262144, is this ok?

Yes.