Problem to write a good serie of bytes in a file.

[philip]

Here is some lines of code than I wrote. You can copy/paste theis code as
code of form1 in a new project.
My problem is this one :
I try to write in a file a serie of bytes.
BUT some bytes written in file are not the sent bytes.
Copy and paste the following lines to observe my problem.
What can I do to resolve problem ?
Only System.Text.Encoding.ASCII write the same number of bytes, but not the
good bytes.
Someone can help me. Thanks by advance.

Public Class Form1
Dim TextBox1 As New TextBox
Dim TextBox2 As New TextBox
Dim Label1 As New Label
Dim Label2 As New Label
Dim Label3 As New Label
Dim Label4 As New Label

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.Size = New System.Drawing.Size(800, 500)

Label1.Location = New System.Drawing.Size(20, 13)
Label1.Text = "Data to write"
Me.Controls.Add(Label1)

Label2.Location = New System.Drawing.Size(20, 40)
Label2.Text = "Data written"
Me.Controls.Add(Label2)

Label3.Location = New System.Drawing.Size(350, 13)
'Label3.Text = "Data written"
Me.Controls.Add(Label3)

Label4.Location = New System.Drawing.Size(350, 40)
'Label4.Text = "Data written"
Me.Controls.Add(Label4)

TextBox1.Size = New System.Drawing.Size(200, 20)
TextBox1.Location = New System.Drawing.Size(120, 13)
Me.Controls.Add(TextBox1)

TextBox2.Size = New System.Drawing.Size(200, 20)
TextBox2.Location = New System.Drawing.Size(120, 40)
Me.Controls.Add(TextBox2)

Dim button1 As New Button
button1.Text = "BinaryWriter encoding ASCII"
button1.Size = New System.Drawing.Size(200, 20)
button1.Location = New System.Drawing.Size(550, 13)
AddHandler button1.Click, AddressOf Button1_Click
Me.Controls.Add(button1)

End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As
System.EventArgs)
Dim Temp As String = "ÿØÿá"
TextBox1.Text = Temp
Label3.Text = "Length to write : " & Temp.Length.ToString & "
octets)"
Dim fullFileName As String = "c:\converted music\test1.jpg"

Dim sw As System.IO.StreamWriter
sw = New System.IO.StreamWriter(fullFileName, False,
System.Text.Encoding.ASCII)
sw.Write(Temp)
sw.Close()

Dim sr As System.IO.StreamReader
sr = New System.IO.StreamReader(fullFileName,
System.Text.Encoding.ASCII)
Do While Not sr.EndOfStream
TextBox2.Text = TextBox2.Text & Chr(sr.Read())
Loop
Label4.Text = "Length written : " & TextBox2.Text.Length.ToString &
" octets)"
sr.Close()
End Sub
End Class

 

[Chris Dunaway]

Keep in mind that ASCII only contains codes from 0 to 127. The
characters you are attempting to write are not part of the ASCII
Encoding. You might try Encoding.Default or Encoding.UTF8 to see if
that helps. Or use the Encoding for the language you are trying to
write.

Hope this helps.

 

[philip]

Thanks for your response.
I explain why I must do that.

I write a program in Visual Studio, in vb, bound to an Access Database.
Some memo field contains exact copy, byte to byte, of 'jpg' files, each file
beeing obviously shorter then 65 k.
What I search to do if to write on a file the bytes loaded in memo file.
I put bytes of memo file in a string and I try to write the bytes in a file
with 'jpg' extension.
If I succeed, I can use image.fromfile(jpgfile) to show the file in a
picture box.

BUT if I use encoding.ASCII, I loose all bytes greater than 127, and I keep
the same number of bytes than the number of bytes of the memo file (and
string). Obviously, And the jpgfile resulting doesn't work. because I lost
all the values greater than 127, replaces by chr63 ='?'

BUT if I use UTF8, bytes are coded in a such way that the binary values of
the file written are not the same, byte by byte, than the binary values of
the string because bytes greater than 127 are coded on 2 bytes, I think. And
the number of bytes is not the same. And the jpgfile resulting doesn't work.

What I search is a way to write all bytes in a file keeping the sale number
of bytes and writing on a byte the values between 0 and 256.
Is it possible ? If it is possible and you have solution, I'm the hapiest
man in the world.
-----------------------------------------
PS : In VBA of Access I can do that like this (and that functions perfectly)
:

Dim lFile1 As Long
Dim Temp1 as string

lFile1 = FreeFile
Open nomFileImageWithChemin For Binary As #lFile1
Put #lFile1, , temp
Close #lFile1

 

[Stan Smith]

I write a program in Visual Studio, in vb, bound to an Access Database.

Some memo field contains exact copy, byte to byte, of 'jpg' files, each
file beeing obviously shorter then 65 k.
What I search to do if to write on a file the bytes loaded in memo file.
I put bytes of memo file in a string and I try to write the bytes in a
file with 'jpg' extension.
If I succeed, I can use image.fromfile(jpgfile) to show the file in a
picture box.

BUT if I use encoding.ASCII, I loose all bytes greater than 127, and I
keep the same number of bytes than the number of bytes of the memo file
(and string). Obviously, And the jpgfile resulting doesn't work. because I
lost all the values greater than 127, replaces by chr63 ='?'

BUT if I use UTF8, bytes are coded in a such way that the binary values of
the file written are not the same, byte by byte, than the binary values of
the string because bytes greater than 127 are coded on 2 bytes, I think.
And the number of bytes is not the same. And the jpgfile resulting doesn't
work.

What I search is a way to write all bytes in a file keeping the sale
number of bytes and writing on a byte the values between 0 and 256.
Is it possible ? If it is possible and you have solution, I'm the hapiest
man in the world.

Philip,

See if this code will increase your happiness . The secret is encoding
and decoding using UTF-16.

You will need:

Imports System.IO
Imports System.Text

a PictureBox named "PictureBox1", a button named "Button1" on your form and
a jpeg file named "In.jpg" in C:\Temp. This code doesn't do any error
handling but I think it will give you a good start.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click

' Read a jpg into a byte array

Dim myBinaryReader As New BinaryReader(File.OpenRead("C:\Temp\In.jpg"))

Dim myByteArray As Byte() =
myBinaryReader.ReadBytes(myBinaryReader.BaseStream.Length)

myBinaryReader.Close()

' Encode the byte array using UTF-16 to a string for storage (in a memo
field?)

Dim myString As String

Dim myUTF16 As New UnicodeEncoding

myString = myUTF16.GetString(myByteArray)

' Decode the string using UTF-16 back to a byte array

myByteArray = myUTF16.GetBytes(myString)

' Convert the byte array to a MemoryStream

Dim myMemoryStream As MemoryStream

myMemoryStream = New MemoryStream(myByteArray, 0, myByteArray.Length)

myMemoryStream.Write(myByteArray, 0, myByteArray.Length)

' Display the image from the MemoryStream

PictureBox1.Image = Image.FromStream(myMemoryStream, True)

' Write the byte array to a new disk file

Dim myBinaryWriter As New BinaryWriter(File.OpenWrite("C:\Temp\Out.jpg"))

myBinaryWriter.Write(myByteArray)

myBinaryWriter.Close()

End Sub

Stan

Stan Smith
ADS Programming Services
2320 Highland Avenue South
Suite 290
Birmingham, AL 35205
205-222-1661
www.adsprogramming.com
ssmith_at_adsprogramming.com

 

[philip]

Thanks for your interest.

1.
I launch you routine, but I have an error on
PictureBox1.Image = Image.FromStream(myMemoryStream, True)
The error is 'Parameter is not valid'. Do you know why ?

2.
I disactivated this problematic line only to see if the remaining part
functions well.
And there is a another problem.
When BinaryReader read 'in.jpg', the array myByteArray is 25864 long (It's
good, it's the length of 'in.jpg').
But when UTF16 codes myByteArray, myByteArray loses some bytes and this
array has now only 25092 elements. So 'out.jpg' is only 25092 bytes long.

And 'in.jpg' is good and visible in pictureBox, but not 'out.jpg'.

I'm a very happy because you approach from truth ands you have interest for
my problem. Can you spend again a lot of time to study these problems ?
Thanks by advance if it's possible.

 

[philip]

I am the happiest man in the world !

Your routine functions ! Just I cut some lines :

Dim myBinaryReader As New BinaryReader(File.OpenRead("C:\in.jpg"))

Dim myByteArray As Byte() =
myBinaryReader.ReadBytes(myBinaryReader.BaseStream.Length)
myBinaryReader.Close()

' Convert the byte array to a MemoryStream
Dim myMemoryStream As MemoryStream
myMemoryStream = New MemoryStream(myByteArray, 0,
myByteArray.Length)
myMemoryStream.Write(myByteArray, 0, myByteArray.Length)
Debug.Print(myMemoryStream.Length)
' Display the image from the MemoryStream
PictureBox1.Image = Image.FromStream(myMemoryStream, True)

' Write the byte array to a new disk file
Dim myBinaryWriter As New BinaryWriter(File.OpenWrite("C:\out.jpg"))
myBinaryWriter.Write(myByteArray)
myBinaryWriter.Close()

Any conversion ASCII ou UTF16

Just one thing : in your routine you begin with a filestream, but I begin
with a string.
I am obliged to transform strin in Array of bytes without any encoder.
I do that :

Dim strImage As String = row.Cells("picture_field").Value.ToString
Dim myByteArray(strImage.Length) As Byte
Dim i As Integer
For i = 0 To strImage.Length - 1
myByteArray(i) = Asc(strImage.Chars(i))
Next
Do you know, to finish to resolve my problem, a better way to do that ?
I am sure that a function exists but I don't know which.
It will be my last question.

Thanks four your help.

Philip