Using GD/Image Functions to Transform Images Stored in a Database

I'm new to the GD/Image functions with PHP, and I'm trying to use them
to manipulate jpeg images that I've stored in a MySQL database
(specifically, creating thumbnails). The thing I can't tell from
reading the documentation is how to use these image functions to
operate on image data -- it looks like you get a GD image resource in
each case by specifying a file name, not by passing image data
directly. While I can see how that's convenient for the common case, I
can't figure out how to make this work without writing the image out
to a file (and since I'm already taking a bit of a performance hit by
reading the image out a database, that seems like the wrong thing to
do). Can anyone elaborate?

notsew-reversePreceedingAndRemoveThis@canncentral.org (Weston C) wrote in message news:<df41fe1.0309130905.2f7cccc6@posting.google.c om>...
> I can't tell from
> reading the documentation is how to use these image functions to
> operate on image data

As it turns out, the helpful folks on php-general suggested the
function "imagecreatefromstring", which seems to be the ticket.
However, I'm having another problem.

The end goal is to create a script that will output the image to the
browser -- and will resize it if given a width value via the query
string. Right now, I have a script that works if I just pass the image
through, but it fails if I try to use the gd library to change the
size.

Here's what I've got:

$row = mysql_fetch_row($dbresult);
$imgdata = $row[0];

if(isset($width) && !empty($width) && is_numeric($width))
/* only do transformation if given a width */
{
$gdimg = imagecreatefromstring($imgdata);
$srcWidth = imagesx($gdimg);
$srcHeight = imagesy($gdimg);
$scaleFactor = $width/$srcWidth;
$targetHeight = $srcHeight * $scaleFactor;

$resizedimg = imagecreatetruecolor($width,$targetHeight);
imagecopyresized($resizedimg,$gdimg,0,0,0,0,$width ,$targetHeight,$srcWidth,$srcHeight);
}

header("Content-Type: image/jpeg");
header("Content-Transfer-Encoding: binary\n");
//send file contents
if(!empty($resizedimg))
imagejpg($resizedimg);
else
{
header("Content-length: " . strlen($imgdata) . "\n");
print($imgdata);
}


Does anyone see what I'm doing wrong? Again, the script actually works
if I
don't try to do the transform. See:

http://www.fsboutah.net/jpg.php?tabl...field=Picture1

and

http://www.fsboutah.net/jpg.php?tabl...ure1&width=100

for contrasts.


-W