Background-clip in CSS3 implements three effects of image cropping (code example)

Goals of this article:

1. Master the 3 implementations of background-clip background cutting

Question:

Required to achieve the following effects, using pure DIV CSS, must Use background-clip

Additional instructions:

1. The width of the photo frame is 500px, the height is 500px, the border is 20px wide, the text padding inside is 20, and the border The size is 20px

2. The image inside is used as the background image of the div

Now let’s do the specific operation

1. Prepare materials: create images in the root directory Folder, store all relevant material pictures here. The materials are

2. Create index.html, write the structure, and how to analyze the structure.

Idea analysis:

1. The goal is divided into 3 parts, upper and lower. Each part actually displays the same photo, so as long as the first photo is completed as required , the others can be copied

2. However, if you look closely, the display of each photo is still different. We found that the second photo is actually cropped based on the first photo. The cropped size is exactly the size of the border, which is equivalent to cropping the border. The third photo is cropped based on the second photo, and the cropped size is exactly the size of the padding inside. In other words, the third picture has removed the parts other than the content, which includes the padding part and the border

3. One part is a block element div, with a title, and then a border and padding. There is a content string, and finally a background image

According to the analysis, we get the following code

     
  
  
裁切效果一
 
 
周慧敏，微微一笑，很倾城
 
 
裁切效果二
 
 
周慧敏，微微一笑，很倾城
 
 
裁切效果三
 
 
周慧敏，微微一笑，很倾城
 
 
  

3. Write the style, create a css folder, and create a new index.css in it , how to write the styles inside, the following is the analysis idea

Think analysis:

1, .container *

Think analysis

1 . In order to set the common styles of all elements in the container, we can write these common codes into the .container * style

So add the following code to index.css:

.container *{ padding:0; margin:0; }

2. photo photo

Idea Analysis

1. According to the requirements, the border is 20px and the dotted line is displayed. The converted code is border-width: 20px; border-style: dashed; the text inside has spacing. , so padding: 20px, font-weight: bold, color is white color: #fff;

The overall width is 500, so width=500-(2 borders 20 20 2 padding20 20)=420, the height is also 420, so width: 420, height: 420

2. Because the border of this photo is dark red, border-color: indianred; and the background is a photo of a beautiful woman , and then it can be seen from the effect that the color between the dotted lines is gray, which is #ccc, so background:#ccc url(../images/Background-clip in CSS3 implements three effects of image cropping (code example)) no-repeat;
The most important thing is that its background image It starts from border, so background-origin: border-box; but the cropping point of each photo is different, but here we can define the common attributes of the photos here

So in index.css Add the code as follows:

.photo { width:420px; height: 420px; border-width:20px; border-style:dashed; padding:20px; font-weight:bold; color:#fff; background:#ccc url(../images/Background-clip in CSS3 implements three effects of image cropping (code example)) no-repeat; border-color: indianred; background-origin: border-box; }

3. 3 different cutting methods

1. The first cutting method is to use the border as the starting point to cut the parts outside the border. So background-clip: border-box;

2. The second cutting method is to use padding as the starting point to cut the parts other than padding, so background-clip: padding-box;

3. The third cutting method is to use content as the starting point to cut the part outside the content, so background-clip: content-box;
So add the following code to index.css:

.clip1{ background-clip: border-box; } .clip2{ background-clip: padding-box; } .clip3{ background-clip: content-box; }

So far, the entire content of index.css is as follows:

.container *{ padding:0; margin:0; } .photo { width:420px; height: 420px; border-width:20px; border-style:dashed; padding:20px; font-weight:bold; color:#fff; background:#ccc url(../images/Background-clip in CSS3 implements three effects of image cropping (code example)) no-repeat; border-color: indianred; background-origin: border-box; } .clip1{ background-clip: border-box; } .clip2{ background-clip: padding-box; } .clip3{ background-clip: content-box; }

Then introduce index.css into index.html

      
  
  
裁切效果一
 
 
周慧敏，微微一笑，很倾城
 
 
裁切效果二
 
 
周慧敏，微微一笑，很倾城
 
 
裁切效果三
 
 
周慧敏，微微一笑，很倾城
 
 
  

The running results are as follows:

So far, we have achieved all the requirements

Summary:

1. Learned 3 ways of background cropping, syntax format Yes

background-clip: border-box | padding-box | content-box | no-clip

border-box: means taking the border as the starting point and cutting the part outside the border

padding-box: means taking padding as the starting point, cutting the part outside the padding

content-box: taking the content as the starting point, cutting the part outside the content

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