Android Question Diffrence size of file in BitmapToString & ImageToBytes & File.ReadBytes

[Masoud44]

Hi everyone
Why is the file size calculation so different in these three methods?

'image8.jpg size 84.5 KB (86,547 bytes)

    Dim bmp As Bitmap
    bmp.Initialize(File.DirAssets, "image8.jpg")
    Log("bmp string length : "&BitmapToString(bmp).Length)                   ' 951116 byte
   
    Dim bb() As Byte=ImageToBytes(bmp)
    Log("bb byte length : "&bb.Length)                                              ' 309169 byte

    Dim buffer() As Byte = File.ReadBytes(File.DirAssets, "image8.jpg")
    Log("buffer byte length : "&buffer.Length)                                   ' 86547 byte

 

[Erel]

Post the code of these methods.

 

[Masoud44]

Post the code of these methods.

Hi Erel

1- BitmapToString(bmp As B4XBitmap)

Private Sub BitmapToString(bmp As B4XBitmap) As String  'XUI
    Dim out As OutputStream
    out.InitializeToBytesArray(1000)
    bmp.WriteToStream(out, 100, "PNG")
    out.Close
    Dim su As StringUtils
    Return su.EncodeBase64(out.ToBytesArray)
End Sub

2- ImageToBytes(Image As Bitmap)

Public Sub ImageToBytes(Image As Bitmap) As Byte()
    Dim out As OutputStream
    out.InitializeToBytesArray(0)
    Image.WriteToStream(out, 100, "JPEG")
    out.Close
    Return out.ToBytesArray
End Sub

3- File.ReadBytes(dir As String, fileName As String)

 

[Erel]

BitmapToString:
1. Uses PNG. Unlike your original JPEG image.
2. It encodes with base64 which adds about 33% overhead (with the advantage of encoding the raw bytes as a valid string).

ImageToBytes does use JPEG. You can play with the quality. It will change the file size.

 

[Masoud44]

It encodes with base64 which adds about 33% overhead (with the advantage of encoding the raw bytes as a valid string).

Thank you for your explanation.
About BitmapToString i got it but what is difference between ImageToBytes(Image As Bitmap) with File.ReadBytes(dir As String, fileName As String) ?
size returned with ImageToBytes over than size returned with File.ReadBytes

 

[Erel]

Different jpeg encoder. Different jpeq quality setting.