Learn about the new attribute object-view-box in CSS3 in one article

This article will take you to have an in-depth understanding of the new feature object-view-box attribute in CSS3, and talk about the role and use of the new attribute. I hope it will be helpful to everyone!

While developing, I always wished there was a native CSS way to crop an image and position it in any direction I needed. This can be achieved by using an additional HTML element and different CSS properties, explained later.

In this article, I will lead you to understand the new CSS property object-view-box proposed by Jake Archibald at the beginning of this year. It allows us to crop or resize the replaced HTML element, like a or <video></video>. [Recommended learning: css video tutorial]

Question

In the example below, we have an image that needs to be cropped. Note that we only want a specific part of the image.

Currently, we can solve this problem in one of the following ways.

• Use <img alt="Learn about the new attribute object-view-box in CSS3 in one article" > and wrap it in an extra element
• Use the image as background-image and modify Position and size

Wrapped in an extra element

This is a common way to solve this problem, the steps are as follows:

• Wrap the image in another element (in our case <figure></figure>).
• Added position: relative and overflow: hidden
• Added position: absolute to the image, and changed the positioning and The size values ​​were adjusted to achieve this result.

<figure>
    <img src="img/brownies.jpg" alt="">
</figure>

figure {
    position: relative;
    width: 300px;
    aspect-ratio: 1;
    overflow: hidden;
    border-radius: 15px;
}

img {
    position: absolute;
    left: -23%;
    top: 0;
    right: 0;
    bottom: 0;
    width: 180%;
    height: 100%;
    object-fit: cover;
}

Put image as background

In this solution we use a

to set the image as background and then we change the position and size value.

<div class="brownies"></div>

.brownies {
  width: 300px;
  aspect-ratio: 3 / 2;
  background-image: url("brownies.jpg");
  background-size: 700px auto;
  background-position: 77% 68%;
  background-repeat: no-repeat;
}

That's fine, but what if we want to apply the above to <img alt="Learn about the new attribute object-view-box in CSS3 in one article" >? Well, that's what object-view-box does.

Introducing Object-View-Box

Attribute object-view-box May be supported in Chrome 104. Now available in Chrome canary.

According to CSS specification (https://drafts.csswg.org/css-images-4/#the-object-view-box)

object-view-box# The ## attribute specifies a "view box" on an element, similar to the attribute, which zooms or pans over the element's content.

The value of this attribute is

= | | . In the demonstration of this article, I will focus on the usage of inset().

Let’s get back to this issue.

With

object-view-box, we can use inset to draw a rectangle from four sides (top, right, bottom, left), and then apply object-fit: cover to avoid deformation.

<img src="img/brownies.jpg" alt="">

img {
    aspect-ratio: 1;
    width: 300px;
    object-view-box: inset(25% 20% 15% 0%);
}

How is this done? Let's look down.

Intrinsic dimensions of the image

The intrinsic size is the default image width and height. The image size I'm working with is

1194 × 1194 px.

img {
    aspect-ratio: 1;
    width: 300px;
}

Using the above CSS, the rendered size of the image will be

300×300px.

Our goal is to draw a rectangle on the inherent image. To do this, we use

inset()values.

Using inset

inset()The values ​​will be based on the width and height of the original image, resulting in a cropped image. It will help us draw an embedded rectangle and control the four edges, similar to handling margin or padding.

inset The value defines an inset rectangle. We can control the four edges, just like we did with margin or padding. In the example below, the card has an inset of 20px on all edges.

Back to

object-view-box:

img {
    aspect-ratio: 1;
    width: 300px;
    object-view-box: inset(25% 20% 15% 0%);
}

Here’s what’s behind the above , the values ​​

25%, 20%, 15% and 0% represent the top, right, bottom and left sides respectively.

修复图像失真

如果图像的尺寸是正方形的，那么裁剪后的结果将是变形的。

这可以使用 object-fit 属性来解决。

img {
    aspect-ratio: 1;
    width: 300px;
    object-view-box: inset(25% 20% 15% 0%);
    object-fit: cover;
}

放大或缩小

我们可以使用 inset 来放大或缩小图像。根据我的测试，过渡或动画不能与object-view-box工作。

我们也可以用一个负的 inset 值来缩小。

想象一下，这对于能够缩放图像是多么有用，而不需要用一个额外的元素来包装它。

事例

地址：https://codepen.io/shadeed/pen/yLvXJRd

期待这个新的属于尽快来了！

作者：ishadeed 

来源：ishadeed

原文：https://ishadeed.com/article/css-object-view-box/

（学习视频分享：web前端）

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