Manipulating image data loaded from SQL database.

[Charlie King]

in brief:
Can I perform operations like imagesx() or getimagesize() on raw image
data as retrieved into a variable from a database, without first
saving it as a file? If so, how? If not, what is the best way to
create a temporary file such that it is unlikely to conflict with
other sessions that are performing the same actions?

in more detail:
I have a database that stores an image in a BLOB field, and I want to
display that image on my page either 'as is' or as a thumbnail created
on the fly to a width passed to the <img...> tag by means of a $_GET
variable - so either
<img src="getimage.p hp?imageid=0123 />
in the first instance, or
<img src="getimage.p hp?imageid=0123 &action=thumb&w idth=200 />
in the second.

I'm getting the image from the database like this:
$photoFetchSour ce = $_GET["imageid"];
$photoFetchQuer y = "SELECT * FROM mytable WHERE
photoid=".$phot oFetchSource;
$photoFetchResu lt = mysql_query($ph otoFetchQuery) or die("blah...");
$photoFetchArra y = mysql_fetch_ass oc($photoFetchR esult;
$photo = $photoFetchArra y["photo"];

and I can send the unchanged photo to the page by

header ("Content-type: image/jpg");
echo $photo;

So far, so good...

Unfortunately, I can't do things like
list($width, $height, $type, $attr) =
getimagesize($p hoto)
because '$photo' isn't a file.

I'd like to avoid any unnecessary file operations if I can. Any
suggestions?

--
Charlie

[Sean]

Not sure if this will work.

Put

//Do the get blob stuff
header ("Content-type: image/jpg");
echo $photo;

In a separate page called something like image.php. You should pass id
values to the page to display different images, so lets say the image
is id value 1, e.g. image.php?id=1.

Then try:

list($width, $height, $type, $attr) = getimagesize('i mage.php?id=1') ;

A better way to do it is not store the images in the database at all,
but store references to the images, and keep the image files on the
file system. By the simple fact you are storing images in the database
you are creating for yourself lots of unnecessary problems.

[Chung Leong]

Use the VariableStream class given as an example here:

http://fi.php.net/manual/en/function...r-register.php

[Charlie King]

On 23 Dec 2005 11:55:47 -0800, in
<11************ **********@g47g 2000cwa.googleg roups.com>
(comp.lang.php) "Chung Leong" <ch***********@ hotmail.com> wrote:

Use the VariableStream class given as an example here:

http://fi.php.net/manual/en/function...r-register.php

Thanks, to you and Sean, for your ideas - I'll try them both out: the
more strings to my bow the better! :)

As it happens, shortly after posting, I found the tool that I needed
for the script I had already built: imagecreatefrom string();

Following on from the example in my first post, now I can do

$im = imagecreatefrom string($photo);

which lets me

$photoWidth = imagesx($im);
$photoHeight = imagesy($im);
list($width, $height, $type, $attr) =getimagesize($ im);
etc.,

Although Sean's point about using the filesystem to store images, and
the database to reference them, seems like a good one given the 2048k
limit I have on LONGBOOLs in MySQL...

Cheers all

--
Charlie

[NC]

Charlie King wrote:

Can I perform operations like imagesx() or getimagesize()
on raw image data as retrieved into a variable from a database,
without first saving it as a file? If so, how?
You can use getimagesize() only on image files. You can, however, use
imagesx() and imagesy() on any image. What you need to do is to pull
data from the database, create an image using imagecreatefrom string()
and feed the resulting image resource to imagesx() and imagesy().
I'm getting the image from the database like this:
$photoFetchSour ce = $_GET["imageid"];
$photoFetchQuer y = "SELECT * FROM mytable WHERE
photoid=".$phot oFetchSource;
$photoFetchResu lt = mysql_query($ph otoFetchQuery) or die("blah...");
$photoFetchArra y = mysql_fetch_ass oc($photoFetchR esult;
$photo = $photoFetchArra y["photo"];

and I can send the unchanged photo to the page by

header ("Content-type: image/jpg");
echo $photo;

So far, so good...

Unfortunately, I can't do things like
list($width, $height, $type, $attr) =
getimagesize($p hoto)
because '$photo' isn't a file.

I'd like to avoid any unnecessary file operations if I can. Any
suggestions?

Two. First, you can do this:

$img = imagecreatefrom string($photo);
$x = imagesx($img);
$y = imagesy($img);
header ("Content-type: image/jpg");
echo $photo; // or imagejpeg($img) ;

Second, if you store images in a database, you may consider storing
image attributes (width, height, and type) in the database as well and
not worry about obtaining them at execution.

Cheers,
NC

[Charlie King]

On 23 Dec 2005 14:08:16 -0800, in
<11************ **********@g43g 2000cwa.googleg roups.com>
(comp.lang.php) "NC" <[e-mail] > wrote:

Charlie King wrote:

Can I perform operations like imagesx() or getimagesize()
on raw image data as retrieved into a variable from a database,
without first saving it as a file? If so, how?
You can use getimagesize() only on image files. You can, however, use
imagesx() and imagesy() on any image. What you need to do is to pull
data from the database, create an image using imagecreatefrom string()
and feed the resulting image resource to imagesx() and imagesy().

Thanks for that - as it turns out, that's exactly where I ended up :)

I'd like to avoid any unnecessary file operations if I can. Any
suggestions?

Two. First, you can do this:

$img = imagecreatefrom string($photo);
$x = imagesx($img);
$y = imagesy($img);
header ("Content-type: image/jpg");
echo $photo; // or imagejpeg($img) ;

Spookily similar to the code I have here! lol
Second, if you store images in a database, you may consider storing
image attributes (width, height, and type) in the database as well and
not worry about obtaining them at execution.
I'd considered that, but there are two issues - a) those dimensions
have to be calculated at some time, and it's as well to do so on the
way out as the way in (although, arguably they'll be extracted more
frequently than they're input...), and b) there is a possibility that
my customer will end up squirting data into the database from
somewhere other than my web front end, and I'd rather be in control
than their supplying good data.
Cheers,
NC

Thanks :)
--
Charlie