I'm currently in the process of making my website AMP-ified my site is built in bootstrap and everything is responsive so most of my images I just set like so:
img{
width:100%;
height:auto;
}
However the problem im running into with my amp-img is that it requires a width and height to be set on the image. What is the correct way of making responsive images with amp is there anyway to do this without setting height and width?
Without knowing the width or height of your image the only way to show your image is to give it the layout attribute fill and wrap it in a element with add which has the following css property object-fit set to contain.
.ampImg__Wrapper {
object-fit: contain;
}
An amp requires the dimensions to be in the tag for a reason
The size you put in there is the size the amp-script uses to generate a placeholder. The placeholder stops the content from jumping around while the images load.
That being said, just put the organic image dimensions in the tag and use the two following properties in your CSS to make sure images play nice
(make sure you add a selector of-course)
{
max-width: 100%;
height: auto;
}
The AMP way to achieve that is by using the layout attribute. In amp-img, you specify the source, the native height and weight ; sourceset with formats, in "css pixels"(e.g. 96px/in) for your responsive image with layout= responsive and you're done. AMP will maintain the h/w ratio.
Ex.
<amp-img
src="/img/small.jpg"
srcset="/img/medium.jpg 640w,
/img/small.jpg 320w"
width="1800"
height="2777"
layout="responsive"
alt="Don't forget to add one">
</amp-img>
In this example, the layout="responsive" would be inferred by the AMP engine because image size and formats are specified. When height and width are not defined, the default layout is "container" (e.g. like plain div).
You can also include amp media queries in amp-img. The preceding example could be set like this:
<amp-img
media="(max-width: 639px)"
src="/img/small.jpg"
width="450"
height="694"
layout="responsive"
alt="Don't forget to add one">
</amp-img>
<amp-img
media="(min-width: 639px)"
src="/img/medium.jpg"
width="900"
height="1388"
layout="responsive"
alt="Don't forget to add one">
</amp-img>
In this case, the "media" attribute will have precedence over the adaptative selection (but it makes almost no practical differences except if you want to force a certain image upon a certain screen size).
For a good overview: https://www.ampbyexample.com/advanced/layout_system/
Hope this help
Related
Google says that it is better to put the width and height of an img in the html: "A web browser can begin to render a page even before images are downloaded"
See Here
<img src="some-address.jpg" width="20px" height="20px">
But, what if the img is in a responsive page?
I did not give any value and the img works well and adapts to any size. But, then the Google testing tool for structured data gives an error: "A value for the width field is required"
https://search.google.com/structured-data/testing-tool
I tried to give that values:
<img src="http://www.w3.org/html/logo/downloads/HTML5_Badge.svg"
width="100%" height="auto">
Here is the example: JSFiddle
It is responsive and it has the values. The error goes away. But I have read that Google requires numeric values.
How to put the width and height of an img in a responsive page?
I suppose that the use of structured data is always recommended. So, I must take into account what the Google testing tool says. Am I right?
This is best done through a css style sheet as the width and height tags for images are generally considered bad practice.
.imageclass{
width: 100%;
max-width: 150px; /* whatever size is the biggest that you want */
height:auto;
}
<img src="http://www.w3.org/html/logo/downloads/HTML5_Badge.svg" class="imageclass" />
Just use css instead of attributes:
img {
width: 100%;
height: auto;
}
<img src="http://www.w3.org/html/logo/downloads/HTML5_Badge.svg">
The article you refer to says:
Specify a width and height for all images. A web browser can begin to render a page even before images are downloaded, provided that it knows the dimensions to wrap non-replaceable elements around. Specifying these dimensions can speed up page loading and improve the user experience. For more information about optimizing your images, see Optimizing Web Graphics on the site Let's Make the Web Faster.
So the reason of specifiing sizes in pixels is that browser will know the image size before it loads the image itself. And there is no sence in specifiing them in css for every image if it is unique and takes all place it needs. Now you are setting one value to auto. With auto browser have to get the image and only then it will be capable to calculate its dimensions ratio and use it. No any reasons to use attributes.
As Unor says here link to a another question
Schema.org’s height/width properties are not for stating in which dimension the image should be displayed, but which dimension the image file has.
So I can put the responsive css as ususal in the css file:
img {
width: 100%;
height: auto;
}
In the html, with structured data I have to give the width and height in px. The real pixels, as I can see in Photoshop:
<div itemprop="image" itemscope itemtype="https://schema.org/ImageObject">
<img src="some-address.jpg"/>
<meta itemprop="url" content="some-address.jpg">
<meta itemprop="width" content="20">
<meta itemprop="height" content="20">
</div>
I found a similar question here, with the answer: "you should always define the width and height in the image tag." But it is from 2009.
In the meantime, many things has changed on frontend. We are all doing responsive page design now, for many devices and sizes simultaneously (mobile, tablet, desktop...).
So, I wonder is it still necessary to specify the width and height attributes, and for what reason (for responsive, page speed, SEO...)?
An img element has width and height attributes, but they're not required under any DOCTYPE.
Width and height attributes were only 'required' or relevant to reserve the space on the page and prevent the page moving around as it loads - which is important. This can be achieved using CSS instead providing the CSS loads quickly enough - it is likely to load before the images anyway, so all should be good.
It is also possible (and valid) to specify just one attribute, width or height and the browser will calculate the omitted value in order to maintain the correct aspect ratio.
You can specify percent values in the attributes if required. You don't need to use CSS for this, if that is what you are implying.
Also, it is relevant to add - Under HTML5 the width and height can only take a pixel value, in other words a valid non-negative integer.
Whether you use the width and height attributes can depend on your design. If you have lots of differently sized images, do you want to lump all the dimensions in the CSS or include them with the img?
YES, you want to declare the width and the height of an image in 2016.
To make them retina-ready
If you want your image to be retina-ready, you should define a width and an height lower than the actual pixels. If the image is 800x600 specify <img width="400" height="300" />.
To avoid page jump
Without the width and the height the image does not know how large it is, which causes an unwanted jump in the page as it loads (it reflows). Declaring height and width solves this problem.
Note that:
Images with a defined width and height can still be responsive. Simply add max-width and max-height to your CSS. This will cause the image to scale down (not up) when it does not fit the screen (see this sweet retina-ready, responsive kitten). Defining a min-width and min-height will do the opposite.
Adding a huge amount of compression to your JPG (around 50%) to keep the file size low is recommended when you use a single (relative large) image for all screen sizes.
Well, the basic answer to this question (as with most coding issues) is this: it depends on the situation at hand.
I would say that the “best practice” of always specifying the height and width attributes of images making a significant difference to page rendering speeds hark back to the days when designers laid out their websites using tables and spacer GIFs. We have come a long way since then.
An indication for the future is the introduction of the new picture element being drafted into HTML. The picture element is effectively a wrapper for the existing img element, which allows you to specify several images of different sizes via a source element, and the user-agent itself actually determines which version is used.
<picture>
<source media="(min-width: 64em)" src="high-res.jpg">
<source media="(min-width: 37.5em)" src="med-res.jpg">
<source src="low-res.jpg">
<img src="fallback.jpg" alt="This picture loads on non-supporting browsers.">
<p>Accessible text.</p>
</picture>
As you can see from this example code above (taken from the Intel Developer Zone's article on the HTML5 picture element) there are no height or width attributes on the img element itself.
Here are a selection of resources that will help you to decide the most appropriate method of declaring image sizes:
Responsive Images Community Group
W3C Working Group Note: Use Cases and Requirements for Standardizing Responsive Images
WHATWG HTML Living Standard: The picture element
Good standards are always worth a recommendation. With a little extra code it's quite easy to merge static (px) values of the img tag and generic (em, %) values supplied by CSS. And simpler still, get rid of the img tag altogether and set the picture as background of a div with a unique ID. If you have multiple images, use sprites and assign each picture to its corresponding div. Your mark-up sources would then look something like <div id="image_001"></div> - that's all. Scales all by itself; no need for bloatware like JQuery, etc.
If we're talking 'bout responsive, you may use bootstrap (if not, start doing this).
When working with images, you should add the class img-responsive, this will modify the width of the image if necessary and the height will be auto, so if width decreases, height will decrease too.
You will always have an image that keeps the same % of its container and will never loose the aspect ratio.
There's no relation with SEO and image size declarations.
Page speed will be the same always, so if the image is 800 x 600 px, you'll load the full image, even if you declare it as 60 x 40 px.
You must think that, even using img-responsive, the max width and height of this image will be the real size of the image. So if we have a 800 x 600 px image, it will not enlarge it (because it'll become loosing quality).
So in 2016, it's recommendable to NOT declare height and width of an image. Instead use bootstrap's img-responsive class, other responsive framework class that gets the same result, or hand-made the proper jquery and css to reach the same.
Hope it helps!
Yes, It is still relevant to specify width and height attribute on images in HTML.
Images often take longer to load than the HTML code that makes up the rest of the page. It is, therefore, a good idea to specify the size of
the image so that the browser can render the rest of the text on the
page while leaving the right amount of space for the image that is
still loading.
Hence, specifying width and height attribute on image will improve the webpage performance by protecting from delay in loading.
Yes, it is necessary to add height and width attributes to the img tag along with the src and alt attributes to prevent page-jumping. When our page loads, the specified space will be preserved for the image so that the it can occupy that place peacefully.
But, there is another problem that will arise here Responsiveness.
Once we give height and width attribute to img tag, the image will tend to stay in the same height for all screen-sizes which will make the image to shrink.
To avoid this, we need to add height: auto; to the image in the CSS file.
I've got a long page, built with Angular. The images on the page are lazy-loaded so that the src is not set until the image is scrolled into view.
The container is flexible and the images should never scale larger than their dimensions (which I know and can set on a style attribute)
Right now I've having issues getting the images without a set source to scale properly.
TL;DR
I want <img src='pic.jpg'/> and <img src=''/>to take up the exact same amount of space inside a flexible container with maximum sizes.
DEMO: http://codepen.io/chrismbarr/pen/xGgGRq?editors=110
HTML (this will be generated from JavaScript where we know the dimentions ahead of time)
<div class="container" style='max-width: 500px; max-height: 700px;'>
Image with a source
<img src="http://lorempixel.com/500/700/cats/2/" />
</div>
<div class="container" style='max-width: 500px; max-height: 700px;'>
Image with no source
<img src="" />
</div>
CSS
img{
display:block;
max-width: 100%;
}
img[src=''],
img:not([src]){
//no image source
height: 100%;
width: 100%;
}
Here's a demo of the image sizes being hard-set so they are no longer flexible. This is what I want to avoid: http://codepen.io/chrismbarr/pen/JdEYMe
In the case that you know the dimensions of every image ahead of time, I almost always recommend the combination of a plain ol' <div> and the background-image property. You don't have to pander to the idiosyncrasies of the <img> tag, and you still get support for animated .gifs.
I whipped up this quick Codepen to give you a feel. I use a directive to set the width and height, which are passed into an isolate scope, then set the background-image property when I detect the directive top offset is less than the height of the window. Quick, dirty, but simple implementation of what I think you're going for.
Advantages:
Aforementioned reprieve from dealing with the ever cantankerous img tag.
Ability to add some neat hover effects (trying hovering over one of the cats in the Codepen).
Drawbacks:
Detecting image load with a background image isn't quite as easy as using the img.onload callback available for image tags. You could likely create directive template that used a img to squeeze out this functionality. Up to you.
Hope this helps!
EDIT: As Chris mentioned in a comment, this technique still doesn't address the aspect ratio issue when the image containers are of varying widths. To solve this I get to whip out one of my favorite CSS tricks, maintaining aspect ratio with padding-bottom, written about by Nicolas Gallagher.
While unfortunately I don't have time to add the fix into my original pen (headed to work), I did create this to show an implementation using the same images. The padding-bottom of an element will proportionally scale as the width of an element increases or decreases, thus maintaining the element's aspect ratio.
that's kinda simple what you do is
<img src="img.jpg" width"20px" height"20px"/>
or any number of pixels and do the same with he other one
<img src="" width"20px" height"20px"/>
This question already has answers here:
Should I specify height and width attributes for my IMGs in HTML?
(5 answers)
Closed 8 years ago.
Is it better coding practice to define an images size in the img tag's width and height attributes?
<img src="images/academia_vs_business.png" width="740" height="382" alt="" />
Or in the CSS style with width/height?
<img src="images/academia_vs_business.png" style="width:740px; height:382px;" alt="" />
Or both?
<img src="images/academia_vs_business.png" width="740" height="382" style="width:740px; height:382px" alt="" />
I'm going to go against the grain here and state that the principle of separating content from layout (which would justify the answers that suggest using CSS) does not always apply to image height and width.
Each image has an innate, original height and width that can be derived from the image data. In the framework of content vs layout, I would say that this derived height and width information is content, not layout, and should therefore be rendered as HTML as element attributes.
This is much like the alt text, which can also be said to be derived from the image. This also supports the idea that an arbitrary user agent (e.g. a speech browser) should have that information in order to relate it to the user. At the least, the aspect ratio could prove useful ("image has a width of 15 and a height of 200"). Such user agents wouldn't necessarily process any CSS.
The spec says that the width and height attributes can also be used to override the height and width conveyed in the actual image file. I am not suggesting they be used for this. To override height and width, I believe CSS (inline, embedded or external) is the best approach.
So depending on what you want to do, you would specify one and/or the other. I think ideally, the original height and width would always be specified as HTML element attributes, while styling information should optionally be conveyed in CSS.
The historical reason to define height/width in tags is so that browsers can size the actual <img> elements in the page even before the CSS and/or image resources are loaded. If you do not supply height and width explicitly the <img> element will be rendered at 0x0 until the browser can size it based on the file. When this happens it causes a visual reflow of the page once the image loads, and is compounded if you have multiple images on the page. Sizing the <img> via height/width creates a physical placeholder in the page flow at the correct size, enabling your content to load asynchronously without disrupting the user experience.
Alternately, if you are doing mobile-responsive design, which is a best practice these days, it's quite common to specify a width (or max-width) only and define the height as auto. That way when you define media queries (e.g. CSS) for different screen widths, you can simply adjust the image width and let the browser deal with keeping the image height / aspect ratio correct. This is sort of a middle ground approach, as you may get some reflow, but it allows you to support a broad range of screen sizes, so the benefit usually outweighs the negative.
Finally, there are times when you may not know the image size ahead of time (image src might be loaded dynamically, or can change during the lifetime of the page via script) in which case using CSS only makes sense.
The bottom line is that you need to understand the trade-offs and decide which strategy makes the most sense for what you're trying to achieve.
While it's ok to use inline styles, your purposes may better be served by including an external CSS file on the page. This way you could define a class of image (i.e. 'Thumbnail', 'Photo', 'Large', etc) and assign it a constant size. This will help when you end up with images requiring the same placement across multiple pages.
Like this:
In your header:
<link type="text/css" rel="stylesheet" href="css/style.css" />
Your HTML:
<img class="thumbnail" src="images/academia_vs_business.png" alt="" />
In css/style.css:
img.thumbnail {
width: 75px;
height: 75px;
}
If you'd like to use inline styles though, it's probably best to set the width and height using the style attribute for the sake of readability.
Definitely not both. Other than that I'd have to say it's a personal preference. I'd use css if I had many images the same size to reduce code.
.my_images img {width: 20px; height:20px}
In the long term CSS may win out due to HTML attribute deprecation and more likely due to the growth of vector image formats like SVG where it can actually make sense to scale images using non-pixel based units like % or em.
<img id="uxcMyImageId" src"myImage" width="100" height="100" />
specifying width and height in the image tag is a good practice..this way when the page loads there is space allocated for the image and the layout does not suffer any jerks even if the image takes a long time to load.
Option a.
Simple straight fwd. What you see is what you get easy to make calculations.
Option b. Too messy to do this inline unless you want to have a site that can stretch. IE if you used the with:86em however modern browsers seem to handle this functionally adequately for my purposes.. . Personally the only time that i would use something like this is if i were to create a thumbnails catalogue.
/*css*/
ul.myThumbs{}
ul.myThumbs li {float:left; width:50px;}
ul.myThumbs li img{width:50px; height:50px;border:0;}
<!--html-->
<ul><li>
<img src="~/img/products/thumbs/productid.jpg" alt="" />
</li></ul>
Option c. Too messy to maintain.
I'm using contentEditable to allow rich text editing in my app. I don't know how it slips through, but when an image is inserted, and then resized (by dragging the anchors on its side), it generates something like this:
<img style="width:55px;height:55px" width="100" height="100" src="pic.gif" border=0/>
(subsequent testing shown that inserted images did not contain this "rogue" style attr+param).
When rendered by the browser (IE7), the width and height in the style overrides the img width/height param (so the image is shown like how I wanted it.. resized to 55px x 55px. So everything went well so it seems.
When I output the page to a ms-word document via setting the mime type application/msword or pasting the browser rendering to msword document, all the images reverted back to its default size. I finally found out that msword is discarding the style and using the img width and height tag (which has the value of the original image size).
Took me a while to found this out. Anyway... I've coded a javascript function to traverse all tags and "transferring" the img style.width and style.height values into the img.width and img.height, then clearing both the values in style, before I proceed saving this piece of html/richtext data into the database.
cheers.
opps.. my answer is.. no. leave both attributes directly under img, rather than style.
If I know the height and width of an image that I'm going to display with an image tag, should I include the height and width attributes, or just put the information in CSS? Or both?
Ex.
<img src="profilepic.jpg" height="64" width="64" />
or
<img src="profilepic.jpg" height="64" width="64" style="height: 64px; width: 64px;" />
or
<img src="profilepic.jpg" style="height: 64px; width: 64px;" />
According to Google Page Speed, you should always define the width and height in the image tag. But, to validate you can't use the style tag.
Also, you should always specify the same height and width as the actual image so the browser doesn't have to do any modifications to it like resizing.
I'd suggest doing it
<img src="..." height="20" width="50">
Edit: Someone suggested in the comments that it would be faster to just not add any attributes. According to Google (not that they are the end all of browser knowledge):
If no dimensions are specified in the containing document, or if the dimensions specified don't match those of the actual images, the browser will require a reflow and repaint once the images are downloaded. To prevent reflows, specify the width and height of all images, either in the HTML tag, or in CSS. - Read More
Given that, you could do the img dimensions in CSS, but to validate you would have to do it in a CSS file, not inline.
BTW, Google Page Speed is a series of tips focused on rendering the page faster.
You should always specify the height and the width of an image if only to help the browser lay the page out even before the image has been downloaded.
See 13.7 Visual presentation of images, objects, and applets in the HTML 4.01 spec:
The height and width attributes give
user agents an idea of the size of an
image or object so that they may
reserve space for it and continue
rendering the document while waiting
for the image data.
They are recommended and not required but you really, really should specify them ;-)
Also, please make sure the dimensions you specify actually match the dimensions of the image.
There is nothing worse than waiting for a page to download just because those 400x300(!) images are in reality more like 4000x3000 at 95% quality.
Yes you should specify the dimensions, so user agents know beforehand the size before the image fully loads so a layout couldn't potentially look broken if it relies on the loaded image's dimensions. In addition, if you're relying on IE6's filter property to insert png's you will need those dimensions.
This answer is now dated and I wouldn't make the same recommendation as I did back in 2009 with modern browsers.
It doesn't really matter which one you use, but I would recommend using only one.
I would recommend the attribute over the css solution as it is more compatible to older browsers and people with styles disabled.
Actually you don't have to specify them. Accordingly to w3c specification you use them only to override default values that are embedded in the image file and are read by the browser. When used will scale the original image to given sizes so putting them is making an extra calculus for the browser.
The height and width attributes give user agents an idea of the size of an image or object so that they may reserve space for it and continue rendering the document while waiting for the image data.
<img src="profilepic.jpg" alt="image" />