Working with binary data

[zagibu]

I have this large binary blob. It's the pixel information of a 32bit bitmap. I'd like to convert it into 24bit by cutting out every fourth byte of the binary blob.

I've had the idea to use BinaryMid($blob, $index, 3) in a loop to get the first three bytes of the blob. But how do I chain all those three-byte pieces together? And how do I cut them out of the blob, so that loop iterations don't get all the same three bytes?

Another idea I had was to use BitShift() and BitOR(), but it seems the blob is too large for BitShift()...

[ProgAndy]

Des this work?

$oldBlob = "0xABCD124EF..."
$newBlob= "0x"
For $i = 1 To BinaryLen($oldBlob) Step 4
    $newBlob &= StringTrimLeft(BinaryMid($oldblob, $i, 3),2)
Next
$newBlob = Binary($newBlob)

[Siao]

If you want to keep it pure AutoIt, you are better off working with that binary data as a hex string, and doing StringRegExpReplace. Any kind of looping (including the one suggested by ProgAndy above) will be pathetically slow on any decent sized data.

Edited May 12, 2008 by Siao