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## How to resize images proportionally / keeping the aspect ratio?

### Question

I have images that will be quite big in dimension and I want to shrink them down with jQuery while keeping the proportions constrained, i.e. the same aspect ratio.

Can someone point me to some code, or explain the logic?

2012/06/13
1
168
6/13/2012 11:31:21 PM

### Accepted Answer

Have a look at this piece of code from http://ericjuden.com/2009/07/jquery-image-resize/

``````\$(document).ready(function() {
\$('.story-small img').each(function() {
var maxWidth = 100; // Max width for the image
var maxHeight = 100;    // Max height for the image
var ratio = 0;  // Used for aspect ratio
var width = \$(this).width();    // Current image width
var height = \$(this).height();  // Current image height

// Check if the current width is larger than the max
if(width > maxWidth){
ratio = maxWidth / width;   // get ratio for scaling image
\$(this).css("width", maxWidth); // Set new width
\$(this).css("height", height * ratio);  // Scale height based on ratio
height = height * ratio;    // Reset height to match scaled image
width = width * ratio;    // Reset width to match scaled image
}

// Check if current height is larger than max
if(height > maxHeight){
ratio = maxHeight / height; // get ratio for scaling image
\$(this).css("height", maxHeight);   // Set new height
\$(this).css("width", width * ratio);    // Scale width based on ratio
width = width * ratio;    // Reset width to match scaled image
height = height * ratio;    // Reset height to match scaled image
}
});
});
``````
2013/10/01
187
10/1/2013 3:13:55 PM

If I understand the question correctly, you don't even need jQuery for this. Shrinking the image proportionally on the client can be done with CSS alone: just set its `max-width` and `max-height` to `100%`.

``````<div style="height: 100px">
<img src="http://www.getdigital.de/images/produkte/t4/t4_css_sucks2.jpg"
style="max-height: 100%; max-width: 100%">
</div>​
``````

Here's the fiddle: http://jsfiddle.net/9EQ5c/

2012/08/31

In order to determine the aspect ratio, you need to have a ratio to aim for. ``````function getHeight(length, ratio) {
var height = ((length)/(Math.sqrt((Math.pow(ratio, 2)+1))));
return Math.round(height);
}
`````` ``````function getWidth(length, ratio) {
var width = ((length)/(Math.sqrt((1)/(Math.pow(ratio, 2)+1))));
return Math.round(width);
}
``````

In this example I use `16:10` since this the typical monitor aspect ratio.

``````var ratio = (16/10);
var height = getHeight(300,ratio);
var width = getWidth(height,ratio);

console.log(height);
console.log(width);
``````

Results from above would be `147` and `300`

2015/05/27

actually i have just run into this problem and the solution I found was strangely simple and weird

``````\$("#someimage").css({height:<some new height>})
``````

and miraculously the image is resized to the new height and conserving the same ratio!

2012/08/07

There are 4 parameters to this problem

1. current image width iX
2. current image height iY
3. target viewport width cX
4. target viewport height cY

And there are 3 different conditional parameters

1. cX > cY ?
2. iX > cX ?
3. iY > cY ?

solution

1. Find the smaller side of the target view port F
2. Find the larger side of the current view port L
3. Find the factor of both F/L = factor
4. Multiply both sides of the current port with the factor ie, fX = iX * factor; fY = iY * factor

that's all you need to do.

``````//Pseudo code

iX;//current width of image in the client
iY;//current height of image in the client
cX;//configured width
cY;//configured height
fX;//final width
fY;//final height

1. check if iX,iY,cX,cY values are >0 and all values are not empty or not junk

2. lE = iX > iY ? iX: iY; //long edge

3. if ( cX < cY )
then
4.      factor = cX/lE;
else
5.      factor = cY/lE;

6. fX = iX * factor ; fY = iY * factor ;
``````

This is a mature forum, I am not giving you code for that :)

2013/07/13

Does `<img src="/path/to/pic.jpg" style="max-width:XXXpx; max-height:YYYpx;" >` help?

Browser will take care of keeping aspect ratio intact.

i.e `max-width` kicks in when image width is greater than height and its height will be calculated proportionally. Similarly `max-height` will be in effect when height is greater than width.

You don't need any jQuery or javascript for this.

Supported by ie7+ and other browsers (http://caniuse.com/minmaxwh).

2014/04/05

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