Is it possible to have a element transparent and see through his parent opaque background

Question

Hi I'm designing a form (HTML / CSS / JS) that pop's over the content when the user wants to subscribe or to login. The whole form background is solid opaque color but I want the inputs to have a transparent background so we can see the content behind the form through it. I don't have any problem setting the inputs transparent but I have no idea of how I can make them "pass through" their parent background color. I begin to think that is impossible with only CSS. I can share code but it's more like a generic question. Thanks

Answer 1

A completely different solution would be to use an <svg>, or even a .png (though that would be an extra http request).

<div class='container is--transparent'>
    <svg>
        # I am the same size as the background and have transparent parts where required
        # Indeed, I could be a div, with a .png background, if you needed to support older browsers
    </svg>
    <input class='input-one' />
    <input class='input-two' />
</div>

Then use css to set:

1. position: absolute; on everything within the background div
2. the svg to be top: 0; left: 0; so it covers the container exactly
3. the inputs to be positioned over the transparent parts in the SVG
4. the backgrounds of the inputs to be transparent

This way everything under the inputs will be transparent and whatever the background is will shine though.

Support for svgs is also excellent, you have to go back to IE8 for there to be a problem.

Answer 2

Yes you can, you can use mask

Support is not perfect, but the fallback is just no transparency, so it degrades nicely. This will also improve with time.

This will allow whatever is behind the element to shine through, flat colour, texture, gradient, multiple elements, images or even video.

Plus, it keeps the style in the css (and images) where it belongs.

I've made a JSFiddle to demonstrate - it's pretty simple really:

<div class="background">
    <div class='masked'>
    </div>
</div>

The markup is there, the background contains the element to be masked. The mask itself is an image made of of black areas of any level of transparency (including fully transparent). Here it is:

The two letter box shapes are the transparent bits which are where the background burns through to the foreground. The bar at the bottom is 50% transparent and serves to demonstrate how alpha values can be used.

The css is here:

.background {
    background: -webkit-gradient(linear, left top, right bottom, color-stop(0%,#959595), color-stop(46%,#0d0d0d), color-stop(50%,#010101), color-stop(53%,#0a0a0a), color-stop(76%,#4e4e4e), color-stop(87%,#383838), color-stop(100%,#1b1b1b));
    width: 250px;
    height: 250px;
    float:left;
}
.masked {
    background: #fff;
    width: 200px;
    margin: 25px;
    height: 200px;
    background-color: #4f6;
    -webkit-mask-image: url(http://stackoverflowimages.excitedstatelaboratory.com/mask-example-image-2.png);
}

You can see some demo specific positioning and size stuff, but what matters is the -webkit-mask-image which works like a background image to find the required png.

We can break the mask image by making it property invalid, which simulates what happens if a browser doesn't understand the property.

Once final point, anything you put in the slots would then have to have it's own background set to transparent in order for the stuff coming through the slots to be visible, but this is easy.

Answer 3

You can cheat by making your input appear to be a cutout, using a few more elements and a little creativity...

Working Example

$('.wrap').draggable();// demo only, used to show off cutout effect. Not necessary 

.wrap {
    position:absolute;
}
.top, .bottom {
    background:grey;
}
input, .top, .bottom {
    width: 100%;
    border: 30px solid grey;
}
input {
    background: transparent;
    color: red;
    border: 29px solid grey;
    outline: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script src="http://code.jquery.com/ui/1.11.4/jquery-ui.min.js"></script>
<div class="wrap">
    <div class="top">This may be cheating, but it works...</div>
    <input type="text" placeholder="testing"/>
    <div class="bottom"></div>
</div>
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Answer 4

Take a look at this solution, https://jsfiddle.net/bnnp2pvj/1/

var color = $('.container').css('background-color');
color = color.replace(')', ', 0.2)').replace('rgb', 'rgba');
$('.background-match').css({"background-color":color});