How to set image size in html

Method: 1. Use the width and height attributes of the img tag, the syntax ""; 2. Use the css width and height attributes, syntax "img{width: value; height: value}".

The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.

Method 1: Use the width and height attributes of the img tag

## The height and width attributes of the tag set the size of the image.

Why use the height and width attributes

Have you ever seen the content of a document appear irregularly when it loads? move. This happens because the browser is constantly re-laying out the page in order to be able to display each loaded image. The browser determines the size of the image by downloading and parsing the width and height of the image, and then leaves a corresponding rectangular space in the display window. The browser then adjusts the display layout of the page to insert the image into the display. This also tells us that the image is an independent file, and it is loaded independently from the source file.

But this is not the most efficient way to display a document, because the browser must check each image file and calculate their screen space before displaying adjacent and subsequent document content. This may cause a very large delay in the display of the document, interrupting the user's reading.

A more efficient method for creators is to specify the dimensions of the image through the height and width attributes of the tag. In this case, the browser reserves a location for the image before downloading it, thus speeding up the display of the document and preventing the document content from moving. Both properties are required to be integer values ​​and represent the image dimensions in pixels. The order in which these two attributes appear in the tag is not important.

Problems with height and width attributes

Although the height and width attributes of the tag can improve performance and allow you to implement some tricks, there is a problem when using them There are still some tricky negative effects. Even if the user has turned off automatic image downloading, the browser still has to display the space reserved for the image in the specified size. What this leaves the reader with is usually an empty frame with a meaningless icon indicating that this is where the image should be placed. At this point the page will look really bad, like it's not finished at all, and most of the content will be useless. If you don't use these specified sizes, the browser will just place an image icon in the text so that at least some text is still readable in the display.

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Method 2: Using the width and height attributes of css

width attribute Set the width of the element, and the height attribute sets the height of the element.

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