How to make an image background transparent using CSS

In web design, setting the background of a picture to be transparent is a common operation. It can make the picture blend with the background of the page to achieve a more natural effect. In this article, we will introduce how to use CSS to set the background of an image to be transparent.

First of all, to set the background transparency of an image, you need to use the CSS property opacity. This attribute can control the transparency of the element, with a value ranging from 0 to 1, where 0 means completely transparent and 1 means completely opaque. When using this attribute, you need to pay attention to the following points:

1. Only ordinary elements (such as
   ) and images () can use the opacity attribute.
2. If the child elements of an element also require transparency, the opacity attribute needs to be redefined in the child elements.
3. On browsers IE8 and below, the opacity attribute is not supported. But you can use IE's dedicated Alpha filter to achieve the same effect.

Now, we demonstrate how to set the image background to be transparent in the following two ways.

1. Using CSS opacity property

We can achieve beautiful image transparency effects through CSS code. For example, the following example:

img {
    opacity: 0.5;
}

The above code sets the transparency of the image to 50%. That is, we can still see the image clearly, but it becomes lighter in color. Of course, you can also set the transparency to other values ​​to achieve the effect you want.

2. Use Alpha filter

As mentioned before, browsers IE8 and below do not support the opacity attribute. But we can use IE-specific filters to achieve the same effect. Here is an example:

img {
    filter: alpha(opacity=50);
    zoom: 1;
}

In the above code, the value of the filter attribute is "alpha(opacity=50)", which means the transparency is 50%. At the same time, we also need to add the zoom:1 attribute. This attribute allows IE6/7 to support the alpha filter. When its value is 1, it means it is turned on.

It should be noted that there is a problem when using the Alpha filter, that is, it will make the picture blurry. This is because the filter will make the entire element transparent, including the font and background, causing the image to become blurry. In order to solve this problem, we can use IE-specific Gradient filter. This filter will apply transparency to the background color without affecting the image itself. Using this filter requires the following definition:

img {
    filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#7F000000,endColorstr=#7F000000);
    zoom: 1;
}

In the above code, startColorstr and endColorstr are the starting and ending points of the transparency gradient, where #7F000000 represents the black color value with a transparency of 50%. This filter also needs to add the zoom:1 attribute.

Through the above introduction, we have learned how to use CSS to set the background of an image to be transparent. No matter which method you use, they can bring a more beautiful effect to your web design.

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