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

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?

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
}
});
});
``````

I think this is a really cool method:

`````` /**
* Conserve aspect ratio of the original region. Useful when shrinking/enlarging
* images to fit into a certain area.
*
* @param {Number} srcWidth width of source image
* @param {Number} srcHeight height of source image
* @param {Number} maxWidth maximum available width
* @param {Number} maxHeight maximum available height
* @return {Object} { width, height }
*/
function calculateAspectRatioFit(srcWidth, srcHeight, maxWidth, maxHeight) {

var ratio = Math.min(maxWidth / srcWidth, maxHeight / srcHeight);

return { width: srcWidth*ratio, height: srcHeight*ratio };
}
``````

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/

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`

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!

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 :)

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).

This should work for images with all possible proportions

``````\$(document).ready(function() {
\$('.list img').each(function() {
var maxWidth = 100;
var maxHeight = 100;
var width = \$(this).width();
var height = \$(this).height();
var ratioW = maxWidth / width;  // Width ratio
var ratioH = maxHeight / height;  // Height ratio

// If height ratio is bigger then we need to scale height
if(ratioH > ratioW){
\$(this).css("width", maxWidth);
\$(this).css("height", height * ratioW);  // Scale height according to width ratio
}
else{ // otherwise we scale width
\$(this).css("height", maxHeight);
\$(this).css("width", height * ratioH);  // according to height ratio
}
});
});
``````

Here's a correction to Mehdiway's answer. The new width and/or height were not being set to the max value. A good test case is the following (1768 x 1075 pixels): http://spacecoastsports.com/wp-content/uploads/2014/06/sportsballs1.png. (I wasn't able to comment on it above due to lack of reputation points.)

``````  // Make sure image doesn't exceed 100x100 pixels
// note: takes jQuery img object not HTML: so width is a function
// not a property.
function resize_image (image) {
var maxWidth = 100;           // Max width for the image
var maxHeight = 100;          // Max height for the image
var ratio = 0;                // Used for aspect ratio

// Get current dimensions
var width = image.width()
var height = image.height();
console.log("dimensions: " + width + "x" + height);

// If the current width is larger than the max, scale height
// to ratio of max width to current and then set width to max.
if (width > maxWidth) {
console.log("Shrinking width (and scaling height)")
ratio = maxWidth / width;
height = height * ratio;
width = maxWidth;
image.css("width", width);
image.css("height", height);
console.log("new dimensions: " + width + "x" + height);
}

// If the current height is larger than the max, scale width
// to ratio of max height to current and then set height to max.
if (height > maxHeight) {
console.log("Shrinking height (and scaling width)")
ratio = maxHeight / height;
width = width * ratio;
height = maxHeight;
image.css("width", width);
image.css("height", height);
console.log("new dimensions: " + width + "x" + height);
}
}
``````

``````\$('#productThumb img').each(function() {
var maxWidth = 140; // Max width for the image
var maxHeight = 140;    // 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 > height){
height = ( height / width ) * maxHeight;

} else if(height > width){
maxWidth = (width/height)* maxWidth;
}
\$(this).css("width", maxWidth); // Set new width
\$(this).css("height", maxHeight);  // Scale height based on ratio
});
``````

If the image is proportionate then this code will fill the wrapper with image. If image is not in proportion then extra width/height will get cropped.

``````    <script type="text/javascript">
\$(function(){
\$('#slider img').each(function(){
var ReqWidth = 1000; // Max width for the image
var ReqHeight = 300; // Max height for the image
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 > height && height < ReqHeight) {

\$(this).css("min-height", ReqHeight); // Set new height
}
else
if (width > height && width < ReqWidth) {

\$(this).css("min-width", ReqWidth); // Set new width
}
else
if (width > height && width > ReqWidth) {

\$(this).css("max-width", ReqWidth); // Set new width
}
else
(height > width && width < ReqWidth)
{

\$(this).css("min-width", ReqWidth); // Set new width
}
});
});
</script>
``````

``````    var width= \$(this).width(), height= \$(this).height()
, maxWidth=100, maxHeight= 100;

if(width > maxWidth){
height = Math.floor( maxWidth * height / width );
width = maxWidth
}
if(height > maxHeight){
width = Math.floor( maxHeight * width / height );
height = maxHeight;
}
``````

Keep in Mind: Search engines don't like it, if width and height attribute does not fit the image, but they don't know JS.

After some trial and error I came to this solution:

``````function center(img) {
var div = img.parentNode;
var divW = parseInt(div.style.width);
var divH = parseInt(div.style.height);
var srcW = img.width;
var srcH = img.height;
var ratio = Math.min(divW/srcW, divH/srcH);
var newW = img.width * ratio;
var newH = img.height * ratio;
img.style.width  = newW + "px";
img.style.height = newH + "px";
img.style.marginTop = (divH-newH)/2 + "px";
img.style.marginLeft = (divW-newW)/2 + "px";
}
``````

The resize can be achieved(maintaining aspect ratio) using CSS. This is a further simplified answer inspired by Dan Dascalescu's post.

http://jsbin.com/viqare

``````img{
max-width:200px;
/*Or define max-height*/
}``````
``````<img src="http://e1.365dm.com/13/07/4-3/20/alastair-cook-ashes-profile_2967773.jpg"  alt="Alastair Cook" />

<img src="http://e1.365dm.com/13/07/4-3/20/usman-khawaja-australia-profile_2974601.jpg" alt="Usman Khawaja"/>``````

2 Steps:

Step 1) calculate the ratio of the original width / original height of Image.

Step 2) multiply the original_width/original_height ratio by the new desired height to get the new width corresponding to the new height.

This issue can be solved by CSS.

``````.image{
max-width:*px;
}
``````

This totally worked for me for a draggable item - aspectRatio:true

``````.appendTo(divwrapper).resizable({
aspectRatio: true,
handles: 'se',
stop: resizestop
})
``````

Resize to fit the container, get scale factor, scale down percentage control

`````` \$(function () {
let ParentHeight = 200;
let ParentWidth = 300;
\$("#Parent").width(ParentWidth).height(ParentHeight);
\$("#ParentHeight").html(ParentHeight);
\$("#ParentWidth").html(ParentWidth);

var RatioOfParent = ParentHeight / ParentWidth;
\$("#ParentAspectRatio").html(RatioOfParent);

let ChildHeight = 2000;
let ChildWidth = 4000;
var RatioOfChild = ChildHeight / ChildWidth;
\$("#ChildAspectRatio").html(RatioOfChild);

let ScaleHeight = ParentHeight / ChildHeight;
let ScaleWidth = ParentWidth / ChildWidth;
let Scale = Math.min(ScaleHeight, ScaleWidth);

\$("#ScaleFactor").html(Scale);
// old scale
//ChildHeight = ChildHeight * Scale;
//ChildWidth = ChildWidth * Scale;

// reduce scale by 10%, you can change the percentage
let ScaleDownPercentage = 10;
let CalculatedScaleValue = Scale * (ScaleDownPercentage / 100);
\$("#CalculatedScaleValue").html(CalculatedScaleValue);

// new scale
let NewScale = (Scale - CalculatedScaleValue);
ChildHeight = ChildHeight * NewScale;
ChildWidth = ChildWidth * NewScale;

\$("#Child").width(ChildWidth).height(ChildHeight);
\$("#ChildHeight").html(ChildHeight);
\$("#ChildWidth").html(ChildWidth);

});``````
``````        #Parent {
background-color: grey;
}

#Child {
background-color: red;
}
``````
``````<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="Parent">
<div id="Child"></div>
</div>

<table>
<tr>
<td>Parent Aspect Ratio</td>
<td id="ParentAspectRatio"></td>
</tr>
<tr>
<td>Child Aspect Ratio</td>
<td id="ChildAspectRatio"></td>
</tr>
<tr>
<td>Scale Factor</td>
<td id="ScaleFactor"></td>
</tr>
<tr>
<td>Calculated Scale Value</td>
<td id="CalculatedScaleValue"></td>
</tr>
<tr>
<td>Parent Height</td>
<td id="ParentHeight"></td>
</tr>
<tr>
<td>Parent Width</td>
<td id="ParentWidth"></td>
</tr>
<tr>
<td>Child Height</td>
<td id="ChildHeight"></td>
</tr>
<tr>
<td>Child Width</td>
<td id="ChildWidth"></td>
</tr>
</table>``````