HTMLImageElement.lowsrc - Web APIs 编辑

Obsolete

This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

Non-standard

This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The HTMLImageElement interface's obsolete lowsrc property can be used to specify the URL of a reduced-quality or otherwise faster-loading version of the image specified by the src property.

This property reflects the HTML lowsrc attribute.

Syntax

htmlImageElement.lowsrc = imageUrl;
imageUrl = htmlImageElement.lowsrc;

Value

A DOMString specifying the URL of a version of the image specified by src which has been modified in some fashion so that it loads significantly more quickly than the primary image.

There are a number of ways to achieve this; primary among them:

• Higher compression levels (for example, a primary image saved as a JPEG using 85% quality might have a lowsrc version saved at 15%.
• Reduced color depth; a primary image in 32-bit color might have an alternate image in 8-bit color.

Important: The lowsrc property is obsolete and should not be used. Instead, you should use an image format which loads progressively (such as progressive JPEG). Or make sure your images are all well-optimized and balanced for appearance versus size.

Usage notes

lowsrc is a strange case. It was never technically part of the HTML specification (it was a Mozilla extension to HTML); however, HTML 5 does list it among the obsolete attributes.