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Using srcset, we can provide multiple image sources for different responsive resolutions and pixel densities. In this video, we'll learn how to implement the srcset attribute in Workspaces.
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Before we jump back into our work space,
let's check out the Mozilla developer
0:00
network documentation for the source set
attribute.
0:04
You can find a link to the MDN docs in the
notes associated with this video.
0:09
So, here I have the Mozilla Developer
Network documentation open.
0:14
And you'll see that we have this srcset
attribute here.
0:21
And right here, it says this is a list of
one or more strings separated by commas,
0:25
indicating a set of possible images for
the user agent to use.
0:31
Each string is composed of a URL to the
image, and
0:37
optionally there is white space followed
by either a width descriptor.
0:41
So that is a positive integer followed by
a w.
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Or, a pixel density descriptor.
0:51
And that is a positive floating point
number followed by An x so
0:55
that would be something like one x or two
x and so on.
1:00
So, lets see what this looks like in work
spaces.
1:05
So I'm gonna close this, first,
1:08
lets try out the pixel density descriptor.
1:12
So, right here, Inside of the div, with
the class profile description.
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I'm going to open that up, and inside of
there, I'm going to say div with the class
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profile-image and we've already set up
some styling for this in our CSS.
1:30
Basically, this will just be floated to
the left,
1:36
with a little bit of margin, I think.
1:40
And inside of here, we're going to open up
an image element,
1:42
and then this is a self closing element.
1:50
And I'm going to.
1:53
Hit enter a couple of times here to make
some space to work
1:55
because we're going to put a couple of
attributes inside of the image element.
1:58
So first, I'm going to use a normal source
and
2:04
we'll go inside of the image folder here
and
2:10
I have a file called photo-@ one x,
2:13
with a dash, and that's a JPEG image.
2:18
And then I'll give it an alt attribute.
2:24
And I'll say this is a photograph of a
flower.
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Okay, I'll delete that extra space there.
2:33
So let's just save that out and switch
back to our preview and
2:36
hit refresh and now we can see that normal
one x image there.
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So far so good.
2:46
However the screen that I'm using here is
actually a retina display,
2:47
so this is at two x.
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So it can advantage of two x images.
2:55
So lets go back to our work space and
2:59
we're going to add these source set
attribute.
3:02
And inside of source set I'm going to type
a couple of sources.
3:07
I'll say image slash photo and
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I'll use that same one x image, so we'll
say at one x
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dot JPEG, and then followed by a space.
3:23
I'll give a pixel density descriptor so
there's a space and
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then a one and an x now, if we save this
and refresh in our preview,
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we should see that this is not quite
right.
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That's because we need to add an x there.
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Let's refresh, and there we go.
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So, that's actually a good way of knowing
that Chrome is indeed using
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the source set and not the source
attribute.
3:56
The reason we want to leave this here is
for
4:01
legacy browsers that do not yet recognize
the source set attribute.
4:03
We do have the poly fill, but just in case
that fails.
4:08
We have the regular source attribute there
however,
4:12
we also want to include a two x image and
if we go into our images folder.
4:16
You can see that we have this nice two x
image there.
4:20
So let's get that in there.
4:24
And the way we do that is by using this
same source set attribute and
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we want the two x image to come first.
4:32
And we don't want two source sets, we just
want the one.
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So we're going to use those same quotes,
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and we'll say img/photo-@2x.jpeg.
4:45
And then a space followed by the pixel
density descriptor, so two x.
4:49
And then we'll put a comma there, and that
comma is going to separate.
4:55
These two different source images.
5:00
So if we save that out, we go back to the
browser.
5:03
Right now I can see some JPEG artifacts
here,
5:06
but if I refresh the page those go away.
5:10
And that's telling me that, that is
actually this two x image.
5:13
Now I can test this really quick, by
putting in one of our other images.
5:18
So lets tell the browser that actually our
two x image is
5:23
maybe this banner small.jpeg picture so,
5:28
lets just say banner small.jpeg I'll save
that out and when I go back and
5:33
refresh, now it's actually putting that
banner image in there.
5:38
So we know that this pixel density
descriptor is working.
5:42
So I'm just going to undo that and leave
it at that two x image and
5:46
there we go now lets add that banner up at
the top
5:52
using a width descriptor so will go back
here and
5:57
just outside of our content block here,
6:02
we're going to add an image and we'll
close that just like that.
6:09
And again we're going to create some space
here using enter and,
6:18
I'll give this a normal source to start
out.
6:23
So this is image slash banner, and
6:25
we'll use the medium resolution one for
the fallback.
6:29
And then, for the alt attribute, I'll say
Photograph of
6:36
Nick Pettit in front of some trees there
we go.
6:39
So lets save that and see if that's
working.
6:45
Okay, there's our image there.
6:48
I also need to give this a class
6:49
in our CSS called banner image.
6:54
So lets see if that's being applied.
6:59
There we go.
7:02
Now we have some better spacing there.
7:03
And now we need to use source set to give
these proper images so
7:06
let's say image slash banner dash large
dot jpeg.
7:14
And instead of using the pixel density
descriptor I'm going to use a width
7:21
descriptor.
7:26
Now, let's take a look at this image.
7:28
It's 20 48 across.
7:31
So that is the width that I want to use.
7:34
I want to tell the browser what the width
of this image is before it loads it.
7:36
And I'll explain that a little bit more
clearly in a moment but
7:42
lets just go ahead and finish typing this
out.
7:45
So we'll say img/banner-medium.jpeg.
7:48
And I know that's 1400 across.
7:52
And I'll put another comma there and list
out a third and final image,
7:55
hold banner-small.jpeg, and that is 800
across.
8:00
So, let's save that out and refresh the
browser.
8:09
And there you can see I'm actually getting
the large crop here and
8:14
that is what I was hoping for.
8:18
Now, you might be wondering, why are these
width descriptors necessary?
8:21
Shouldn't the browser know the width of an
image?
8:25
Well, the browser doesn't know the width
of an image until it's completely
8:28
downloaded so, we need to tell the
browser, hey, this source image is going
8:32
to be this wide, and that way it can
intelligently select the correct source.
8:37
One other thing I should point out is that
the behavior
8:43
of the source-set attribute is somewhat
unique in Google Chrome,
8:47
because Chrome is one of the few browsers
that supports this feature natively.
8:51
Chrome will always use the largest image
available in the cache.
8:57
A simple way to always keep the cache
clear while working
9:02
is to always keep the dev tools open.
9:06
So if we go ahead and
9:09
open up the dev tools, we can go to the
network tab here.
9:13
And there's a little checkbox that says
disable cache.
9:18
So we want to make sure that that is
checked and when we refresh the page,
9:22
Chrome will pull in the latest image so
let's re size the browser here.
9:29
And we'll go to one of these smaller sizes
and you'll see that it's still
9:36
using that large image, which really isn't
appropriate for this smaller size.
9:41
However, because we have the dev tools
open, and the cache is disabled.
9:46
We'll refresh, and now Chrome only knows
about this smallest image,
9:51
because it pulled the appropriate one,
using the source set attribute.
9:57
However, if I re size the browser you'll
see that it now popped to the medium crop,
10:02
and if I keep going you'll see that now
it's at the large crop.
10:10
And that's the largest image we have
available.
10:16
But once again, if I go down to the
smallest size It's still going
10:18
to use that large crop until I refresh the
page with the cache disabled.
10:23
So if you refresh the page, and you don't
see any change.
10:28
Make sure that you have the dev tools
open, and that your cache is clear.
10:32
Behavior will be different in other
browsers that are using the poly fill.
10:37
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