Extension:PageImages/zh

The PageImages extension collects information about images used on a page.

Its aim is to return the single most appropriate thumbnail associated with an article.

Since MediaWiki 1.29, PageImages provides OpenGraph protocol metadata for articles on the wiki for 3rd parties like Facebook to extract.

API
The PageImages extension provides image information by adding a  to the  API for.

配置
$wgPageImagesDenylist is an array of sources for image denylists. Listed images will never be selected as page images. Examples:

More than one source can be used at the same time.

The denylist itself should contain wikilinks to files, the rest of the content is irrelevant (and can contain links to other pages). 例如：

Remember that file links that result in images being added to the page will not work (these files are denylisted for a reason, right?), so don't forget the  in front of the links.

$wgPageImagesDenylistExpiry determines how long the list will remain cached, in seconds. Default: 15 * 60 (15 minutes).

$wgPageImagesExpandOpenSearchXml if set to true, PageImages will override the image detection in the  API module with its own, more accurate results. 默认为“false”.

$wgPageImagesNamespaces is an array of namespaces PageImages will be activated on. 默认为“NS_MAIN”.

After the change, you'll have to run to generate the Page image information for those namespaces (hopefully, you can use the --namespace parameter to process only pages on the affected namespaces, since that script is very resource-intensive)

工作原理
When a page is saved with a local image, the parser runs the hooks  and. The PageImages extension responds to these (and other hooks) and inserts a new property for the page into the table. The property name is  and its value is the name of the image.

The extension only stores the chosen image name. Other features may display the image, such as Page information, Hovercards, and Mobile search while typing.

How can I check which image is associated with a page?
Page images will be listed on the ?action=info page.

How does it select images?
All images in the page are collected and a score for each image is calculated. The image with the highest score is selected as the page image. If the wiki is configured such that images contain metadata that specifies images are not freely licensed, the image with the best score that is also freely licensed is also stored. If no suitable image is found or all the images score badly (i.e. has a negative score), the page will not have any images.

If $wgPageImagesLeadSectionOnly is true, only images in the lead section will be considered. Currently it is true for only Wikipedia projects, all other projects can pull images from outside the lead.

How are images scored?
The best possible page image on Wikimedia wikis is one of the first four images in an article which has a width/height between 400-600px and a height/width which is twice the value of the other dimension.


 * The algorithm is configurable.
 * Scores are calculated by a combination of:
 * Image widths as defined in
 * In Wikimedia wikis, images smaller than 119 pixels are weighted highly negatively. Images with widths between 400px-600px are favoured, with a preference for the lower bound.
 * Images inside galleries are scored separately using
 * In Wikimedia wikis gallery images which are smaller than 100 are disregarded.
 * Position in document is also considered as defined in
 * On Wikimedia wikis, only the first 4 images that appear in the document are considered.
 * The ratio of the image's width to height is considered
 * On Wikimedia wikis the best possible images are images where the height is half the width or the height is double the width. Any images for which the ratio is less than 0.5 will score negatively and be discarded.

Be more technical, please...
Pageimages populates images whenever the hook runs.

In PageImages this is executed in LinksUpdateHookHandler::doLinksUpdate

Can I exclude certain page images?
Yes! There is a list on every wiki that administrators can edit, at MediaWiki:Pageimages-denylist (example). Any images that appear here will not be page images for any article.

What about just for one particular article?
Sadly not at the current time. Please use the denylist or move the image outside the lead section.

How can I see the page image for a page?
Using the  link in the sidebar (or adding  to the URL) you'll be able to see the current image choice.

如何清除不良图像？
仅当文章中的链接更改时，页面图像才会更改. 对于紧急情况，请在页面中添加/删除链接，必要时进行恢复. 清除页面将不起作用. 对于较大的紧急情况，请提交Phabricator门票.

为什么我的页面图像是空白框？
这可能与您文章中的视频内容有关. 如果视频文件以空白屏幕开头，则它将成为视频的默认缩略图，并且如果用作页面图像，它将成为页面图像. 我们目前正在对此进行修复，使您可以更改视频的默认缩略图. 有关更多信息，请参见：phab:T92457和phab:T22647.

Upgrade notes

 * Since MediaWiki 1.37,  and   have been renamed to   and   respectively. There's no backwards compatibility code added to accept the old variable names, which means you should change the variable names during the upgrade, or define both variables in advance in preparation for the upgrade.
 * Since MediaWiki 1.37, the default page value for  has been changed from   to  . If you've added content to   on your wiki, you should rename it during the upgrade. If you want to prepare in advance for the upgrade, you can rename the page to the new name, and also set   (the old variable name) to the new page name, and the default value will be used when upgrading, which should match your previous change.