Обсуждение: Re: Displaying Image BLOBs

> From: Herouth Maoz <herouth@oumail.openu.ac.il>
(zip)
> In short, you should have a cgi whose URL may look something like:
>
>     http://my.domain.com/cgi-bin/lo-dumper.cgi?oid=NNNNN&mime=image/jpeg
>
> When you have one, you can use it as your image source. Just write your
> image output with the above URL as its source:
>
>    <IMG SRC="/cgi-bin/lo-dumper.cgi?oid=123456@mime=image/jpeg"
>     WIDTH=100 HEIGHT=40 ALT="Image of a bear">
>
> How did all the parameters get there? Well, I assume that anybody holding
> an image database will have an image table, which has fields for the image
> name or details (which can be used in the ALT), its width and height, and
> if there are several image types, also its type (jpeg, gif, png).

Keeping information about sizes of images might be embarrassing,
though I think there's on CPAN Perl modules to learn from an image
it's size, jpeg or gif alike (not sure).

But people might prefer using only the WIDTH *or* the HEIGHT
parameter; Netscape and Explorer will then keep the image ratio
when displaying the image.

My 2 cents ;)
Fabrice

At 18:01 +0200 on 26/01/1999, Fabrice Scemama wrote:


> Keeping information about sizes of images might be embarrassing,
> though I think there's on CPAN Perl modules to learn from an image
> it's size, jpeg or gif alike (not sure).
>
> But people might prefer using only the WIDTH *or* the HEIGHT
> parameter; Netscape and Explorer will then keep the image ratio
> when displaying the image.

I guess we're drifting off-topic, but for those who write this sort of
program for embedding images in HTML pages, it's important to know:

If you explicitly state the full size (width and height) in the IMG tag,
your browser will be able to allocate the needed screen space even before
the image loads. Therefore, if all the images in your page are tagged with
their sizes, the browser is able to display the page's text before loading
the images.

This causes the users to have an early feedback - they see that "something
is coming through", thus takes some frustration away and gives an illusion
of speed. If you don't do things this way, the text will not show until the
last of the unsized images have loaded.

In a similar vain, avoid using a large tables that contain the rest of your
page's contents. Netscape waits for the </TABLE> before it displays the
page, which means none of the contents will show until the page is fully
loaded. It's better to decompose things into smaller tables and just align
them. This advice is useful for those who want to display database results
on an HTML page.

Herouth

--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma