Android Question How to convert a Base64 string into a Image file

[elitevenkat]

From Mysql table i have synchronized data containing BLOB field through php script using base64_encode function.
in my B4A app, in JOB_DONE sub i am decoding the BLOB data as follows

Case GetA
                ProgressDialogShow("fetching default question from Server")
                Dim rows As List
                rows = parser.NextArray
            
               If rows.Size >0 Then   
                    Dim ListOfMaps As List
                    ListOfMaps.Initialize
  
                   For i = 0 To rows.Size - 1          
                       Dim m As Map        
                           
                        m =  rows.Get(i)
                       
                       m.Put("eimg", su.DecodeBase64(m.Get("eimg")))  ' eimg is the BLOB field
                       
                        ListOfMaps.Add(m)
   
                   Next
                   Job.Release                 
                    DBUtils.InsertMaps(SQL, "AMASTER", ListOfMaps)

then i am looping through the Sqlite table and saving the BLOB data to a file as below

    Dim Buffer() As Byte
     
       For i = 0 To Cursor1.RowCount - 1
           Cursor1.Position = i
           
           Buffer=Cursor1.GetBlob("eimg")
            Dim InputStream1 As InputStream
            InputStream1.InitializeFromBytesArray(Buffer, 2, Buffer.Length)
           Dim ou As OutputStream
           ou=File.OpenOutput(File.DirRootExternal,i& ".png",True)
         
           File.Copy2(InputStream1,ou)
           ou.Flush
           ou.Close 
       Next
    End If
    Cursor1.Close

The png files are saved in the device. However i am unable to open the image files. The photo / alum viewer reports "unable to show image...." error

where is the problem ? in converting and storing BLOB data ?

 

[Roycefer]

Try using this library: https://b4x.com/android/forum/threads/base64-encode-decode-image-library.31031/

 

[eurojam]

even when the code is right, blob fields are limited in size: see this for more information http://stackoverflow.com/questions/12716859/retrieve-large-blob-from-android-sqlite-database
The image will be corrupted, if your bas64 string will be to long

 

[Erel]

My guess is that the data you receive is already corrupted.
Check it with this code:

Dim b() As Byte = su.DecodeBase64(m.Get("eimg"))
Dim in As InputStream
in.InitializeFromBytesArray(b, 0, b.Length)
Dim bmp As Bitmap
bmp.Initialize2(in)

 

[elitevenkat]

My guess is that the data you receive is already corrupted.
Check it with this code:

Dim b() As Byte = su.DecodeBase64(m.Get("eimg"))
Dim in As InputStream
in.InitializeFromBytesArray(b, 0, b.Length)
Dim bmp As Bitmap
bmp.Initialize2(in)

yes the image data is corrupt. i am getting bitmap error .... after testing with your code. Wonder how you always conclude correctly !!!

 

[Erel]

Wonder how you always conclude correctly !!!

The code that inserts the data to the database and the code that retrieves it look correct. So we are left with the actual data.

 

[elitevenkat]

Yes agreed...