Changing image sizes proportionally using CSS

This is a known problem with CSS resizing. Unless all images have the same proportion, you have no way to do this via CSS.

The best approach would be to have a container, and resize one of the dimensions (always the same) of the images. In my example I resized the width.

If the container has a specified dimension (in my example the width), when telling the image to have the width at 100%, it will make it the full width of the container. The auto at the height will make the image have the height proportional to the new width.

Example:

HTML:

<div class="container">
    <img src="something.png" />
</div>

<div class="container">
    <img src="something2.png" />
</div>

CSS:

.container {
    width: 200px;
    height: 120px;
}

/* Resize images */
.container img {
    width: 100%;
    height: auto;
}

You need to fix one side (for example, height) and set the other to auto.

For example,

 height: 120px;
 width: auto;

That would scale the image based on one side only. If you find cropping the image acceptable, you can just set

overflow: hidden;

to the parent element, which would crop out anything that would otherwise exceed its size.

You can use the object-fit CSS 3 property. Something like:

It is not exactly your answer, though, because it doesn't stretch the container. But it behaves like the gallery and you can keep styling the img itself.

Another drawback of this solution is still a poor support of the CSS 3 property. More details are available here: CSS 3 Object-fit Polyfill. A jQuery solution can be found there as well.

To make images adjustable/flexible you could use this:

/* fit images to container */
.container img {
    max-width: 100%;
    height: auto;
}

If you don't want to stretch the image, fit it into a div container without overflow and center it by adjusting its margin if needed.

The image will not get cropped The aspect ratio will also remain the same.

HTML

<div id="app">
    <div id="container">
      <img src="#" alt="something">
    </div>
    <div id="container">
      <img src="#" alt="something">
    </div>
    <div id="container">
      <img src="#" alt="something">
    </div>
</div>

CSS

div#container {
    height: 200px;
    width: 200px;
    border: 1px solid black;
    margin: 4px;
}
img {
    max-width: 100%;
    max-height: 100%;
    display: block;
    margin: 0 auto;
}

Put it as a background on your holder e.g.

<div style="background:url(path/to/image/myimage.jpg) center center; width:120px; height 120px;">
&nbsp;
</div>

This will center your image inside a 120x120 div chopping off any excess of the image

transform: scale(0.5);

Example:

<div>Normal</div>
<div class="scaled">Scaled</div>

div {
  width: 80px;
  height: 80px;
  background-color: skyblue;
}

.scaled {
  transform: scale(0.7); /* Equal to scaleX(0.7) scaleY(0.7) */
  background-color: pink;
}

See scale().

This helps me to make the image 150% with ease.

.img-popup img {
  transform: scale(1.5);
}

Now this should be more as a last resort, but you could simply do math. For example, lets say that you have an image with a width of 595 and height of 300. You would create a unit rate by doing 300/595 = 0.504. Then, you would plug in a width that you would like to change the image to (1000px). 1000 x 0.504 = 504. This means that the height of the image should be 504 if the width is 1000 if you want to keep it proportional.

If you know the aspect ratio, you can use padding-bottom with percentage to set the height depending on the width of the diff.

<div>
   <div style="padding-bottom: 33%;">
      I have 33% height of my parents width
   </div>
</div>