Question

I am trying to copy an image as a byte array to a file in vba.

The first three bytes of the file, represented as a byte array:

   Dim arr(3) As Byte arr = {23,21,2f}

The code that copies from an array to a new file is:

Open "try444.jpg" For Binary As #1

For cnt = 1 To UBound(arr)

    Put #1, LOF(1) + 1, arr(cnt)

Next

but it writes 1100 2311 0023 1100 2111 002f 1100 to the file (all in hex)

What is wrong with my code?

Answer 1

because arr is being redefined somewhere. If I write the procedure as a single function:

Option Explicit
Sub test()
Dim cnt As Long
Dim arr(3) As Byte

arr(1) = &H23
arr(2) = &H21
arr(3) = &H2F

Open "try444.jpg" For Binary As #1

For cnt = 1 To UBound(arr)

    Put #1, LOF(1) + 1, arr(cnt)

Next
Close #1

End Sub

then I get exactly the bytes you would expect 23 21 2F

If I neglect to define the type (or I don’t have Option Explicit) then it becomes a variant, and then it’s anyone’s guess as to what will appear, as the variant datatype includes a type code. (in my case, I get 02 00 23 00 02 00 21 00 02 00 2f 00)