Getting width and height from a picture file

[Joaquim Amado Lopes]

Greetings.

Is there any way, in Javascript, to put in 2 variables the width and
height of a picture, given the filename and without the picture being
displayed in the webpage?

Thank you,
Joaquim Amado Lopes

[Evertjan.]

Joaquim Amado Lopes wrote on 07 feb 2008 in comp.lang.javas cript:

Is there any way, in Javascript, to put in 2 variables the width and
height of a picture, given the filename and without the picture being
displayed in the webpage?

Just put the img outside the viewable window

style='position :absolute;left:-1000px;'

and then measure it.

I think.

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[Joaquim Amado Lopes]

Greetings.

On 06 Feb 2008 23:06:41 GMT, "Evertjan."
<ex************ **@interxnl.net wrote:

>Is there any way, in Javascript, to put in 2 variables the width and
height of a picture, given the filename and without the picture being
displayed in the webpage?

Just put the img outside the viewable window

style='positio n:absolute;left :-1000px;'

and then measure it.

I think.

It's not practical for what I need.

I have a form to publish articles, in which the user chooses the
picture to display with the article.
The list of pictures is collected from a folder and presented in a
SELECT form field. As the user chooses one of the items on the list
(onChange), that picture is previewed.

As some of the pictures may be quite large and must be previewed with
reduced dimensions, I need to know the dimensions of each picture
before displaying it, to determine the width and height of the preview
and maintain the proportions.

Cheers,
Joaquim Amado Lopes

[Joost Diepenmaat]

Joaquim Amado Lopes <ja*****@jalope s.net.writes:

Greetings.

On 06 Feb 2008 23:06:41 GMT, "Evertjan."
<ex************ **@interxnl.net wrote:

>>Is there any way, in Javascript, to put in 2 variables the width and
height of a picture, given the filename and without the picture being
displayed in the webpage?

Just put the img outside the viewable window

style='positi on:absolute;lef t:-1000px;'

and then measure it.

I think.

It's not practical for what I need.

I have a form to publish articles, in which the user chooses the
picture to display with the article.
The list of pictures is collected from a folder and presented in a
SELECT form field. As the user chooses one of the items on the list
(onChange), that picture is previewed.

As some of the pictures may be quite large and must be previewed with
reduced dimensions, I need to know the dimensions of each picture
before displaying it, to determine the width and height of the preview
and maintain the proportions.

Then you may be out of luck: to determine the dimensions you *will* have
to examine the content of the image stream. How much of the content
you'll need is dependent on the type of image. You may need most or all
of it.

You could possibly be able to hack something together for the major file
types using Ajax, but I would suggest you move all of that to the
server, where there are plenty of libraries and resources that will
handle this much better.

Joost.

[Joaquim Amado Lopes]

Greetings.

On Thu, 07 Feb 2008 00:42:31 +0100, Joost Diepenmaat <jo***@zeekat.n l>
wrote:
[snip]

>I have a form to publish articles, in which the user chooses the
picture to display with the article.
The list of pictures is collected from a folder and presented in a
SELECT form field. As the user chooses one of the items on the list
(onChange), that picture is previewed.

As some of the pictures may be quite large and must be previewed with
reduced dimensions, I need to know the dimensions of each picture
before displaying it, to determine the width and height of the preview
and maintain the proportions.

Then you may be out of luck: to determine the dimensions you *will* have
to examine the content of the image stream. How much of the content
you'll need is dependent on the type of image. You may need most or all
of it.

You could possibly be able to hack something together for the major file
types using Ajax, but I would suggest you move all of that to the
server, where there are plenty of libraries and resources that will
handle this much better.

I wasn't clear in my previous post. The images are on the server.
The upload part is already working.

Cheers,
Joaquim Amado Lopes

[Joost Diepenmaat]

Joaquim Amado Lopes <ja*****@jalope s.net.writes:

>>As some of the pictures may be quite large and must be previewed with
reduced dimensions, I need to know the dimensions of each picture
before displaying it, to determine the width and height of the preview
and maintain the proportions.

Then you may be out of luck: to determine the dimensions you *will* have
to examine the content of the image stream. How much of the content
you'll need is dependent on the type of image. You may need most or all
of it.

You could possibly be able to hack something together for the major file
types using Ajax, but I would suggest you move all of that to the
server, where there are plenty of libraries and resources that will
handle this much better.

I wasn't clear in my previous post. The images are on the server.
The upload part is already working.

Well, if you know the dimensions on the server, just use an Ajax to
fetch them:

http://developer.mozilla.org/en/docs...etting_Started

Note that that text uses XML in the response. It's usually easier and
faster to use a javascript response and eval() it to parse the data.
See also http://www.json.org/

Joost.

[Evertjan.]

Joaquim Amado Lopes wrote on 07 feb 2008 in comp.lang.javas cript:

Greetings.

On 06 Feb 2008 23:06:41 GMT, "Evertjan."
<ex************ **@interxnl.net wrote:

>>Is there any way, in Javascript, to put in 2 variables the width and
height of a picture, given the filename and without the picture being
displayed in the webpage?

Just put the img outside the viewable window

style='positi on:absolute;lef t:-1000px;'

and then measure it.

I think.

It's not practical for what I need.

I have a form to publish articles, in which the user chooses the
picture to display with the article.
The list of pictures is collected from a folder and presented in a
SELECT form field. As the user chooses one of the items on the list
(onChange), that picture is previewed.

As some of the pictures may be quite large and must be previewed with
reduced dimensions, I need to know the dimensions of each picture
before displaying it, to determine the width and height of the preview
and maintain the proportions.

Doing this clientside without downloading seems impossible.

I suppose you better use a serverside javascript solution, like:

http://www.aspjpeg.com/object_aspjpe...OriginalHeight
http://www.aspjpeg.com/object_aspjpe...#OriginalWidth
--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)