Tag omission in text/html : neither tag is omissible. Content attributes : Global attributes. Allowed aria role attribute values : None. Allowed aria state and property attributes : None. Dom interface : interface htmlpictureElement : htmlelement ; The picture element is a container dissertation which provides multiples sources to its contained img element to allow authors to declaratively control or give hints to the user agent about which image resource to use, based on the. It represents its children. The user agent first tries to match an image source contained within the source attribute and use that, but if none is found, it falls back to what is contained within the img element, which must be present. The following example utilizes art direction to provide the appropriate image at a particular viewport for small and large screens.
If the user agent supports WebP images, the first source element will be chosen. If not, but the user agent does support jpeg xr images, the second source element will be chosen. If neither of those formats are supported, oliver the img element will be chosen. Dependencies Media queries mediaq media-condition css values and Units css-values length css syntax css-syntax-3 Parse a comma-separated list of component values component value whitespace-token.7.3. The picture element Categories : Flow content. Contexts in which this element can be used : Where embedded content is expected. Content model : Zero or more source elements, followed by one img element, optionally intermixed with script-supporting elements.
Art direction -based selection The picture element and the source element, together with the media attribute, can be used, to provide multiple images that vary the image content (for instance the smaller image might be a cropped version of the bigger image). picture source media min-width: 45em srcset"g" source media min-width: 32em srcset"g" img src"g" alt"The wolf runs through the snow." /picture the user agent will choose the first source element for which the media query in the media attribute matches, and then choose an appropriate url. The rendered size of the image varies depending on which resource is chosen. To specify dimensions that the user agent can use before having downloaded the image, css can be used. Img width: 300px; height: 300px @media (min-width: 32em) img width: 500px; height:300px @media (min-width: 45em) img width: 700px; height:400px this example combines art direction - and device-pixel-ratio -based selection. A banner that takes half the viewport is provided in two versions, one for wide screens and one for narrow screens. h1 picture source media max-width: 500px srcset"eg, eg 2x" img src"eg" srcset"eg 2x" alt"The Breakfast Combo" /picture /h1 Image format-based selection The type attribute on the source element can be used, to provide multiple images in different formats. h2 From todays featured article /h2 picture source type"image/webp" source type"image/-photo" img src uploads/g" alt"A singer on the stage" width"100" height"150" /picture p a lloyd /a (18701922) was an English a hall /a singer. In this example, the user agent will choose the first source that has a type attribute with a supported mime type.
How to present
In this example, the sizes attribute could be omitted because the default value is 100vw. In this example, the web page has three layouts depending on the width of the viewport. The narrow layout has one column of images (the width of each image is about 100 the middle amaysim layout has two columns of images (the width of each image is about 50 and the widest layout has three columns of images, and some page margin. It breaks between these layouts when the viewport is 30em wide and 50em wide, respectively. img sizes max-width: 30em) 100vw, (max-width: 50em) 50vw, calc(33vw - 100px srcset"g 200w, g 400w, g 800w, g 1600w" src"g" alt"Kettlebell Swing" The sizes attribute sets up the layout breakpoints at 30em and 50em, and declares the image sizes between these breakpoints to be 100vw. These sizes do paper not necessarily have to match up exactly with the actual image width as specified in the css.
The user agent will pick a width from the sizes attribute, using the first item with a media-condition (the part in parentheses) that evaluates to true, or using the last item (calc(33vw - 100px) if they all evaluate to false. For example, if the viewport width is 29em, then (max-width: 30em) evaluates to true and 100vw is used, so the image size, for the purpose of resource selection, is 29em. If the viewport width is instead 32em, then (max-width: 30em) evaluates to false, but (max-width: 50em) evaluates to true and 50vw is used, so the image size, for the purpose of resource selection, is 16em (half the viewport width). Notice that the slightly wider viewport results in a smaller image because of the different layout. The user agent can then calculate the effective pixel density and choose an appropriate resource similarly to the previous example.
For user agents that understand srcset, the src attribute participates in the resource selection, as if it had been specified by srcset with a 1x descriptor. The images rendered size is given in the width and height attributes, which allows the user agent to allocate space for the image before it is downloaded. Viewport-based selection The srcset and sizes attributes can be used, using the w descriptor, to provide multiple images that only vary in their size (the smaller image is a scaled-down version of the bigger image). In this example, a banner image takes up the entire viewport width (using appropriate css). h1 img srcset"g 400w, g 800w, g 1600w" src"g" sizes"100vw" alt"The rad wolf" /h1 The user agent will calculate the effective pixel density of each image from the specified w descriptors and the specified rendered size in the sizes attribute.
It can then choose any of the given resources depending on the users screens pixel density, zoom level, and possibly other factors such as the users network conditions. If the users screen is 320 css pixels wide, this is equivalent to specifying.25x,.5x,. On the other hand, if the users screen is 1200 css pixels wide, this is equivalent to specifying.33x,.67x,.33x. By using the w descriptors and the sizes attribute, the user agent can choose the correct image source to download regardless of how large the users device. For backwards compatibility, one of the urls is specified in the img elements src attribute. In new user agents, the src attribute is ignored when the srcset attribute uses w descriptors.
Io, resume of Santhanam
With this in mind, this specification introduces a number of features to address the above problems in a declarative manner. Device-pixel-ratio -based selection when the rendered size of the image is fixed The src and srcset attributes on the img element can be used, using the x descriptor, to provide multiple images that only vary in their size (the smaller image is a scaled-down version. The x descriptor is not appropriate when the rendered size of the image depends on the viewport width ( viewport-based selection but can be used together with art direction. h2 From todays featured article /h2 img src uploads/g" srcset uploads/g.5x, /uploads/g 2x" alt"A singer on the stage" width"100" height"150" p a lloyd /a (18701922) was an English a hall /a singer. The user agent can choose any of the given resources depending on the users screens pixel density, zoom level, restaurant and possibly other factors such as the users network conditions. To provide backwards compatibility with older user agents that dont understand the srcset attribute, one of the urls is specified in the img elements src attribute. This will result in something useful (though perhaps at a lower-resolution than the user might expect) being displayed even in older user agents.
Authors might want to show the same image content but using different image formats, depending on which animals image formats the user agent supports. This is usually referred to as image format-based selection. A web page might have some images in the jpeg, webP and jpeg xr image formats, as the latter two have better compression abilities compared to jpeg. Since different user agents can support different image formats, with some formats offering better compression ratios, the author would like to serve the better formats to user agents that support them, while providing a jpeg fallback for user agents that dont. The above situations are not mutually exclusive. For example, it is reasonable to combine different resources for different device-pixel-ratio with different resources for art direction. While it is possible to solve these problems using scripting, doing so introduces some other problems: Some user agents aggressively download images specified in the html markup, before scripts have had a chance to run, so that Web pages complete loading sooner. If a script changes which image to download, the user agent will potentially start two separate downloads, which can instead cause worse page loading performance. If the author avoids specifying any image in the html markup and instead instantiates a single download from script, that avoids the double download problem above but instead it makes no image be downloaded at all for users with scripting disabled and it disables the.
top that always spans the entire viewport width. In this case, the rendered size of the image depends on the physical size of the screen (assuming a maximised browser window). Another Web page might have images in columns, with a single column for screens with a small physical size, two columns for screens with medium physical size, and three columns for screens with big physical size, with the images varying in rendered size in each. In this case, the rendered size of an image might be bigger in the one-column layout compared to the two-column layout, despite the screen being smaller. Authors might want to show different image content depending on the rendered size of the image. This is usually referred to as art direction. When a web page is viewed on a screen with a large physical size (assuming a maximised browser window the author might wish to include some less relevant parts surrounding the critical part of the image. When the same web page is viewed on a screen with a small physical size, the author might wish to show only the critical part of the image.
A mobile phones screen might have three times as many physical pixels per inch compared to another mobile phones screen, regardless of their physical screen size. The users' zoom level might be different from one another, or might change for a single user over time. A user might zoom in to a particular image to be able to get a more detailed look. The zoom level and the screen pixel density (the previous point) can both affect the number help of physical screen pixels per css pixel. This ratio is usually referred to as device-pixel-ratio. The users' screen orientation might be different from one another, or might change for a single user over time. A tablet can be held upright or rotated 90 degrees, so that the screen is either "portrait" or "landscape". The users' network speed, network latency and bandwidth cost might be different from one another, or might change for a single user over time. A user might be on a fast, low-latency and constant-cost connection while at work, on a slow, low-latency and constant-cost connection while at home, and on a variable-speed, high-latency and variable-cost connection anywhere else.
Github pages - stack overflow
Introduction, this section is non-normative. To embed an image in html, when there is only a single image resource, use the img element and with its src and alt attributes. h2 From todays featured article /h2 img src uploads/g" alt"A singer on the stage" width"100" height"150" p a lloyd /a (18701922) was an English a hall /a singer. However, there are a number of situations for which the author might wish to use multiple image resources that the user agent can choose from: Different users might have different make environmental characteristics: The users' physical screen size might be different from one another. A mobile phones screen might be 4 inches diagonally, while a laptops screen might be 14 inches diagonally. This is only relevant when an images rendered size depends on the viewport size. The users' screen pixel density might be different from one another.