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jpeg image to byte array

Posted on 2006-07-04
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Can anybody give me an example of how I can store a jpeg image (either from the filesystem or from a SQL BLOB) into a byte array in VB6?
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Question by:Tricky3
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7 Comments
 
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Expert Comment

by:BrianGEFF719
ID: 17039739
Here is code that will open a jpeg, read it into a byte array, then write out the byte array to another file:

Option Base 1
Private Sub Form_Load()
Dim strFilePath As String
Dim lngFileSize As Long
Dim dblFree As Double
Dim byteArray() As Byte

strFilePath = "c:\file.jpg"

dblFree = FreeFile
Open strFilePath For Binary As #dblFree
    lngFileSize = LOF(dblFree)
    ReDim byteArray(lngFileSize)
    Get #dblFree, 1, byteArray()
Close #dblFree
   
Open "c:\output.jpg" For Binary As #2
    Put #2, 1, byteArray()
Close #2

   
   
End Sub
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by:Tricky3
ID: 17039782
Thanks for that - I'll accept the answer, but was hoping you may be able to help me take this one step further.

Is there any way I could add additional data to this array, eg text and even some more images?

The get function appears to just overwrite the entire array..

Thanks again

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BrianGEFF719 earned 1000 total points
ID: 17039801
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LVL 19

Expert Comment

by:BrianGEFF719
ID: 17045782
>> The get function appears to just overwrite the entire array..

Acctually the ReDim erases the whole array. If you add the keyword 'Preserve' after the word ReDim, it will Redimension the array and preserve the contents. Make sense?
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Author Comment

by:Tricky3
ID: 17046798
It does make sense thanks, I realised this afterwards.

As I need a mixture of JPEG & Text data (for eventually posting as a multipart form via xmlhttp) I am using 2 byte arrays. One I use to collect each individual text/jpeg portion and i then copy it into the second array which is the final version that gets posted. It's working fine this way.

Thanks for your help.

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LVL 19

Expert Comment

by:BrianGEFF719
ID: 17047352
I see, you will likely run across problems if you turn the data into a string, its common to find null terminators in binary files which will terminate a string.

brian
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Author Comment

by:Tricky3
ID: 17047370
Thanks Brian,

You're spot on - that's exactly what was happening originally (had me baffled for a while) which is why I went for the byte array option. Thankfully you can pass the whole byte array to the send method of the xmlhttp object for the post.

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