Posted by Bint on 08/10/06 20:30

How do I use PHP to create a binary array of data? Specifically, I need to
create an image array ( a string of 16 bit integers that is width*height in
size). I've got a data array coming in as an outside argument which is
run-length-encoded image data. I can read that image data using ord and bit
shifting to put my 16 bit values together, but I don't know how to plug them
into a new array (or binary string?). What I am looking for is a binary
string, I guess, not a php array. Can anyone tell me how to do that?

Here's the routine I wrote, which doesn't work. Particularly I don't think
I should be creating my binary string elements with output[$indexnumber].
That is creating a key-value array. I thought about using pack, but here I
need to pack values into a single array over and over in for loops--I can't
do it all at once. Is there a way to pack a single value and then append it
to a binary string that I slowly "grow"?

Thanks
B


function rle_decode(&$data, $length)
{
$forceit = 1;
$outnum = 0;

for ($pnum = 0; $pnum < $length; ) {
$cur = (ord($data{$pnum*2}) << 8) + ord($data{$pnum*2+1});
$pnum++;
$output[$outnum++] = $cur;

/* check for run */
if (($forceit == 0)&&($cur == $prev))
{
/* we have a run. write it out. */
$count = (ord($data{$pnum*2}) << 8) + ord($data{$pnum*2+1});
$pnum++;
while ($count > 0)
{
$output[$outnum++] = $cur;
$count--;
}

$forceit = 1;
}
else
{
/* no run */
$prev = $cur;
$forceit = 0;
}
}

return $output;
}

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