Question about Preloading images

[michaaal]

Is this the correct way to preload an image...?

Var Image1 = new Image()

....And then when I'm ready to use the image I can do this...?

Button1.src=Ima ge1.src

....Or am I just telling Button1 to use the same source path as Image1?

[Randy Webb]

Re: Question about Preloading images

michaaal wrote:
[color=blue]
> Is this the correct way to preload an image...?
>
> Var Image1 = new Image()[/color]

var is case sensitive, its lower-case v

And you have forgotten to define the src attribute to the new Image()
you just created.

Image.src='url to Image';
[color=blue]
> ....And then when I'm ready to use the image I can do this...?
>
> Button1.src=Ima ge1.src
>
> ....Or am I just telling Button1 to use the same source path as Image1?[/color]

With the above additions, now you can.

--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq

[Thomas 'PointedEars' Lahn]

Re: Question about Preloading images

Randy Webb wrote:
[color=blue]
> michaaal wrote:[color=green]
>> Is this the correct way to preload an image...?
>>
>> Var Image1 = new Image()[/color]
>
> var is case sensitive, its lower-case v
>
> And you have forgotten to define the src attribute to the new Image()
> you just created.
>
> Image.src='url to Image';[/color]

Image1.src = ...
^
Otherwise a property would be added to the constructor.
[color=blue][color=green]
>> ....And then when I'm ready to use the image I can do this...?
>>
>> Button1.src=Ima ge1.src
>>
>> ....Or am I just telling Button1 to use the same source path as Image1?[/color]
>
> With the above additions, now you can.[/color]

Yes, indeed :)

Yet it is not a very good way of preloading images, if there is some
(preloading should be done very careful -- not only that is is not really
required, it is unreliable [because my cache is *my* cache and client-side
scripting may be disabled/restricted/not present] and if it works it forces
users to download data they do not requested), it is unreliable,
error-prone and quite hard to maintain. I have been working on another
approach that does not show most of these problems:

<http://pointedears.de/scripts/test/hoverMe>


PointedEars

[Randy Webb]

Re: Question about Preloading images

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> Randy Webb wrote:
>
>[color=green]
>>michaaal wrote:
>>[color=darkred]
>>>Is this the correct way to preload an image...?
>>>
>>>Var Image1 = new Image()[/color]
>>
>>var is case sensitive, its lower-case v
>>
>>And you have forgotten to define the src attribute to the new Image()
>>you just created.
>>
>>Image.src='ur l to Image';[/color]
>
>
> Image1.src = ...
> ^
> Otherwise a property would be added to the constructor.
>[/color]

True, was a typo.
[color=blue][color=green][color=darkred]
>>>....And then when I'm ready to use the image I can do this...?
>>>
>>>Button1.src= Image1.src
>>>
>>>....Or am I just telling Button1 to use the same source path as Image1?[/color]
>>
>>With the above additions, now you can.[/color]
>
>
> Yes, indeed :)
>
> Yet it is not a very good way of preloading images, if there is some
> (preloading should be done very careful -- not only that is is not really
> required, it is unreliable [because my cache is *my* cache and client-side
> scripting may be disabled/restricted/not present] and if it works it forces
> users to download data they do not requested), it is unreliable,
> error-prone and quite hard to maintain. I have been working on another
> approach that does not show most of these problems:
>
> <http://pointedears.de/scripts/test/hoverMe>[/color]

If you want a non-script way of loading images:

<img src="theImage.j pg" width="1" height="1" alt="">

And its a 1 pixel dot on the page, but the image gets loaded, unless
images are disabled and then it doesn't really matter.


--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq

[Thomas 'PointedEars' Lahn]

Re: Question about Preloading images

Randy Webb wrote:
[color=blue]
> If you want a non-script way of loading images:
>
> <img src="theImage.j pg" width="1" height="1" alt="">[/color]

That may be viable for graphical browsers,
not for other types of user agents.


PointedEars

[Randy Webb]

Re: Question about Preloading images

Thomas 'PointedEars' Lahn wrote:[color=blue]
> Randy Webb wrote:
>
>[color=green]
>>If you want a non-script way of loading images:
>>
>><img src="theImage.j pg" width="1" height="1" alt="">[/color]
>
>
> That may be viable for graphical browsers,
> not for other types of user agents.[/color]

And why would you need to preload/cache images in a non-graphical user
agent?

--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq

[Thomas 'PointedEars' Lahn]

Re: Question about Preloading images

Randy Webb wrote:
[color=blue]
> Thomas 'PointedEars' Lahn wrote:[color=green]
>> Randy Webb wrote:[color=darkred]
>>> If you want a non-script way of loading images:
>>>
>>> <img src="theImage.j pg" width="1" height="1" alt="">[/color]
>>
>> That may be viable for graphical browsers,
>> not for other types of user agents.[/color]
>
> And why would you need to preload/cache images in a non-graphical user
> agent?[/color]

You would not but the display of those "img" elements intended merely for
preloading/caching could be disturbing anyway. Text browsers like lynx
or links, e.g., can be configured to display "img" elements as a link for
downloading the image resource as a file (to be displayed by user-defined
graphics viewer software, for example).


PointedEars