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changing image size on roll over

P: n/a
I have been trying to write a script that will increase the size of
and image when you mouse over it, and decrease it to original size,
when you mouse out. After a couple of attempts, this is what I've come
up with. In this example, there are 5 images (0 thru 4) all with a
height of 80px. When you mouse over an image, it changes the
growingImage variable equal to the number of the image you mouse over,
when you mouse out, it sets it to 5, which means none of the images,
and runs the chechSize function. All this works fine, except every
time you mouse over an image, the time it takes to grow and shrink
decreases, until it is instantly jumping from small to large, without
transition. Any help fixing that bug would be appreciated, or if you
know a better solution to this problem, I'd love to hear it. Kenny
Here's my code. I only included one image, but there all similar.

var growingImage = 5;
var i = 0;

function resizeImage(imageNumber) {
document.images[imageNumber].height -= 1
document.images[imageNumber].width -= 1
}

function increaseSizeImage(imageNumber) {
document.images[imageNumber].height += 1
document.images[imageNumber].width += 1
}

function checkSize() {
if ((i == growingImage) && (document.images[i].height < 90)) {
increaseSizeImage(i)
}
if ((i != growingImage) && (document.images[i].height !=80)) {
resizeImage(i)
}
i++
if (i == 5) {i = 0}
setTimeout("checkSize()", 10)
}

<a href="#" onMouseOver="growingImage=0;checkSize()"
onMouseOut="growingImage=5;checkSize()"><img src="../images/Adora.jpg"
width="60" height="80" border="0" /></a>
Jul 20 '05 #1
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4 Replies


P: n/a
DU
Kenny wrote:
I have been trying to write a script that will increase the size of
and image when you mouse over it, and decrease it to original size,
when you mouse out.
[snipped]

Any help fixing that bug would be appreciated, or if you know a better solution to this problem, I'd love to hear it. Kenny


[snipped]

Here's a draft version of what I would do. The following code is valid,
has been tested and is working on Mozilla 1.5 final, K-meleon 0.8, MSIE
6 SP1 for Windows and Opera 7.23. I'm loading the file here since I have
now banner ads on my site and want to avoid that for now until I can
find another solution.
The file is a draft version because I would register event handlers for
the image(s) instead of using event attributes like in the same spirit
of this file:

Continuous modification of an image's opacity
http://www10.brinkster.com/doctorunc...icOpacity.html

Also, your file as submitted was using an embedding anchor for the
image: now, the events could be registered on the image or on the
anchor. The difference is in accessibility and usability: the default
border around links would still need to be there if link is used. I also
saw other usability issues: resorting to setTimeout(expr, 10) is way too
demanding on several systems. I personally never go under 32 msec to
avoid crashes on the users' system: some video cards and system
resources can not perform safely, confortably with DHTML at less than
32msec. In any case, animations faster than 32msec are too fast for the
eyes. If your increase/decrease height needs to be "faster", than
increase the step from 1 to 2 or more. I.e.:
document.getElementById("idImage").height += 2;

DU

---------------

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-us">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta http-equiv="Content-Language" content="en-us" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta http-equiv="Content-Script-Type" content="text/javascript" />
<meta http-equiv="date" content="2003-12-02T09:54:03+08:00" />
<meta http-equiv="imagetoolbar" content="no" />

<title>Dynamically enlarge image on mouseover and mouseout</title>

<style type="text/css">
body {margin:64px;}
</style>
<script type="text/javascript">
// <![CDATA[
var glbInc, glbDec;

function decreaseSizeImage() // will get back to its normal default size
{
if(glbInc != null) {clearTimeout(glbInc); glbInc = null;};
if (document.getElementById("idImage").height > 111)
{
document.getElementById("idImage").height -= 1;
document.getElementById("idImage").width -= 1;
glbDec = setTimeout("decreaseSizeImage()", 32);
};
}

function increaseSizeImage()
{
if(glbDec != null) {clearTimeout(glbDec); glbDec = null;};
if (document.getElementById("idImage").height < 150)
{
document.getElementById("idImage").height += 1;
document.getElementById("idImage").width += 1;
glbInc = setTimeout("increaseSizeImage()", 32);
};
}
// ]]>
</script>

</head>

<body>

<p><a href="#" onmouseover="increaseSizeImage();"
onmouseout="decreaseSizeImage();"><img id="idImage"
src="http://www10.brinkster.com/doctorunclear/GRAPHICS/JPG/KrustyHelpless.jpeg"
width="113" height="111" alt="Krusty is helpless" /></a></p>

<p id="validation"><a href="http://validator.w3.org/check/referrer"><img
src="http://www.w3.org/Icons/valid-xhtml10.png" title="Verify this
page's markup syntax" alt="Valid XHTML 1.0!" /></a> <a
href="http://jigsaw.w3.org/css-validator/check/referer"><img
src="http://www.w3.org/Icons/valid-css.png" title="Verify this page's
CSS code" alt="Valid CSS!" /></a> <a
href="http://www.webstandards.org"><img
src="http://www10.brinkster.com/doctorunclear/GRAPHICS/GIF/webstandardsproject.gif"
alt="Web standards project" /></a></p>

</body></html>

DU

Jul 20 '05 #2

P: n/a
DU
DU wrote:
Kenny wrote:
I have been trying to write a script that will increase the size of
and image when you mouse over it, and decrease it to original size,
when you mouse out.

[snipped]

Any help fixing that bug would be appreciated, or if you
know a better solution to this problem, I'd love to hear it. Kenny

[snipped]

Here's a draft version of what I would do. The following code is valid,
has been tested and is working on Mozilla 1.5 final, K-meleon 0.8, MSIE
6 SP1 for Windows and Opera 7.23. I'm loading the file here since I have
now banner ads on my site and want to avoid that for now until I can
find another solution.
The file is a draft version because I would register event handlers for
the image(s) instead of using event attributes like in the same spirit
of this file:

Continuous modification of an image's opacity
http://www10.brinkster.com/doctorunc...icOpacity.html
Also, your file as submitted was using an embedding anchor for the
image: now, the events could be registered on the image or on the
anchor. The difference is in accessibility and usability: the default
border around links would still need to be there if link is used. I also
saw other usability issues: resorting to setTimeout(expr, 10) is way too
demanding on several systems. I personally never go under 32 msec to
avoid crashes on the users' system: some video cards and system
resources can not perform safely, confortably with DHTML at less than
32msec. In any case, animations faster than 32msec are too fast for the
eyes. If your increase/decrease height needs to be "faster", than
increase the step from 1 to 2 or more. I.e.:
document.getElementById("idImage").height += 2;

DU

---------------

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-us">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta http-equiv="Content-Language" content="en-us" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta http-equiv="Content-Script-Type" content="text/javascript" />
<meta http-equiv="date" content="2003-12-02T09:54:03+08:00" />
<meta http-equiv="imagetoolbar" content="no" />

<title>Dynamically enlarge image on mouseover and mouseout</title>

<style type="text/css">
body {margin:64px;}
</style>
<script type="text/javascript">
// <![CDATA[
var glbInc, glbDec;

function decreaseSizeImage() // will get back to its normal default size
{
if(glbInc != null) {clearTimeout(glbInc); glbInc = null;};
if (document.getElementById("idImage").height > 111)
{
document.getElementById("idImage").height -= 1;
document.getElementById("idImage").width -= 1;
glbDec = setTimeout("decreaseSizeImage()", 32);
};
}

function increaseSizeImage()
{
if(glbDec != null) {clearTimeout(glbDec); glbDec = null;};
if (document.getElementById("idImage").height < 150)
{
document.getElementById("idImage").height += 1;
document.getElementById("idImage").width += 1;
glbInc = setTimeout("increaseSizeImage()", 32);
};
}
// ]]>
</script>

</head>

<body>

<p><a href="#" onmouseover="increaseSizeImage();"
onmouseout="decreaseSizeImage();"><img id="idImage"
src="http://www10.brinkster.com/doctorunclear/GRAPHICS/JPG/KrustyHelpless.jpeg"
width="113" height="111" alt="Krusty is helpless" /></a></p>

<p id="validation"><a href="http://validator.w3.org/check/referrer"><img
src="http://www.w3.org/Icons/valid-xhtml10.png" title="Verify this
page's markup syntax" alt="Valid XHTML 1.0!" /></a> <a
href="http://jigsaw.w3.org/css-validator/check/referer"><img
src="http://www.w3.org/Icons/valid-css.png" title="Verify this page's
CSS code" alt="Valid CSS!" /></a> <a
href="http://www.webstandards.org"><img
src="http://www10.brinkster.com/doctorunclear/GRAPHICS/GIF/webstandardsproject.gif"
alt="Web standards project" /></a></p>

</body></html>

DU


There is also this file

Dynamic magnification of an image:
http://www10.brinkster.com/doctorunc...MSIE6Zoom.html

but it only works in MSIE 6 for windows (it might work also in MSIE 5.5)
because Mozilla based browsers do not have an equivalent to MSIE's
proprietary style zoom property.
But then it would be easy to make that code work by modifying the image
width and height.
The difference with your code is that here there is no anchor
surrounding the image and the image size is entirely under the user's
control via a mouse drag, which I think is more pleasing for the user.

DU

Jul 20 '05 #3

P: n/a
DU
DU wrote:
DU wrote:

There is also this file

Dynamic magnification of an image:
http://www10.brinkster.com/doctorunc...MSIE6Zoom.html

but it only works in MSIE 6 for windows (it might work also in MSIE 5.5)
because Mozilla based browsers do not have an equivalent to MSIE's
proprietary style zoom property.
But then it would be easy to make that code work by modifying the image
width and height.
The difference with your code is that here there is no anchor
surrounding the image and the image size is entirely under the user's
control via a mouse drag, which I think is more pleasing for the user.

DU


I created an entirely new file which works very well for MSIE 6 for
Windows, Mozilla 1.5, K-meleon 0.8, Opera 7.23 and should work for all
DOM 2 compliant browsers. It works on a click and drag (up or down) user
interaction. The markup and CSS code would be entirely valid if it was
not of the banner ad include.

http://www10.brinkster.com/doctorunc...ification.html

DU

Jul 20 '05 #4

P: n/a

"Kenny" <ke*********@email.com> wrote in message
news:3d**************************@posting.google.c om...
I have been trying to write a script that will increase the size of
and image when you mouse over it, and decrease it to original size,
when you mouse out. After a couple of attempts, this is what I've come
up with. In this example, there are 5 images (0 thru 4) all with a
height of 80px. When you mouse over an image, it changes the
growingImage variable equal to the number of the image you mouse over,
when you mouse out, it sets it to 5, which means none of the images,
and runs the chechSize function. All this works fine, except every
time you mouse over an image, the time it takes to grow and shrink
decreases, until it is instantly jumping from small to large, without
transition. Any help fixing that bug would be appreciated, or if you
know a better solution to this problem, I'd love to hear it. Kenny
Here's my code. I only included one image, but there all similar.

var growingImage = 5;
var i = 0;

function resizeImage(imageNumber) {
document.images[imageNumber].height -= 1
document.images[imageNumber].width -= 1
}

function increaseSizeImage(imageNumber) {
document.images[imageNumber].height += 1
document.images[imageNumber].width += 1
}

function checkSize() {
if ((i == growingImage) && (document.images[i].height < 90)) {
increaseSizeImage(i)
}
if ((i != growingImage) && (document.images[i].height !=80)) {
resizeImage(i)
}
i++
if (i == 5) {i = 0}
setTimeout("checkSize()", 10)
}

<a href="#" onMouseOver="growingImage=0;checkSize()"
onMouseOut="growingImage=5;checkSize()"><img src="../images/Adora.jpg"
width="60" height="80" border="0" /></a>


I see your problem. When you do a mouseover, you register a timeout, that
continues to register itself again, and does not stop. When you do another
mouseover, you register a second timeout, which continues to register
itself, causing the function to be called twice as often, making it work
twice as fast. The same pattern continues to happen, until there are so
many callbacks registered, that the action happens almost immediately.

There are two ways to solve this... Either put some conditional logic around
the setTimeout call, to stop calling it when your action is done... or save
the ID that setTimeout returns in a global variable, and call clearTimeout
on that value for each mouseover, thus killing the previous routine.

My guess is that a combination of both options will be most useful... The
first one to stop the timeout from occuring when it is no longer needed, and
the second one to make sure if the first one is still running, it gets
killed, so two are not running at the same time.

Brian
Jul 20 '05 #5

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