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CSS Masking

With CSS masking you create a mask layer to place over an element to partially or fully hide portions of the element.

The CSS mask-image Property​

The CSS mask-image property specifies a mask layer image.

The mask layer image can be a PNG image, an SVG image, a CSS gradient, or an SVG <mask> element.

CSS Masking Properties​

The following table lists all the CSS masking properties:

PropertyDescription
mask-imageSpecifies an image to be used as a mask layer for an element
mask-modeSpecifies whether the mask layer image is treated as a luminance mask or as an alpha mask
mask-originSpecifies the origin position (the mask position area) of a mask layer image
mask-positionSets the starting position of a mask layer image (relative to the mask position area)
mask-repeatSpecifies how the mask layer image is repeated
mask-sizeSpecifies the size of a mask layer image

Use an Image as the Mask Layer​

To use a PNG or an SVG image as the mask layer, use a url() value to pass in the mask layer image.

The mask image needs to have a transparent or semi-transparent area. Black indicates fully transparent.

.mask {  
	-webkit-mask-image:  url(my-mask.png);  
	mask-image:  url(my-mask.png);  
	-webkit-mask-repeat:  no-repeat;  
	mask-repeat:  no-repeat;  
}

Explanation:

  • The mask-image property specifies the image to be used as a mask layer for an element.
  • The mask-repeat property specifies if or how a mask image will be repeated. The no-repeat value indicates that the mask image will not be repeated (the mask image will only be shown once).
  • The image on which to apply the mask use class="mask"

Example masking with image

Use Gradients as the Mask Layer​

CSS linear and radial gradients can also be used as mask images.

Linear Gradient Examples​

Example of a linear gradient used as a mask layer

.mask1 {  
	-webkit-mask-image:  linear-gradient(black, transparent);  
	mask-image:  linear-gradient(black, transparent);  
}

Radial Gradient Examples​

Example of a radial gradient used as a mask layer

.mask {  
	-webkit-mask-image:  radial-gradient(circle, black 50%, rgba(0, 0, 0, 0.5) 50%);  
	mask-image:  radial-gradient(circle, black 50%, rgba(0, 0, 0, 0.5) 50%);  
}

Use SVG as the Mask Layer​

The SVG <mask> element can be used inside an SVG graphic to create masking effects.

Example of a SVG mask layer with a triangle shape:

<svg width="600" height="400">  
	<mask id="svgmask1">  
		<polygon fill="#ffffff"  points="200 0, 400 400, 0 400"></polygon>  
	</mask>  
	<image xmlns:xlink="http://www.w3.org/1999/xlink"  xlink:href="img_5terre.jpg"  mask="url(#svgmask1)">	</image>  
</svg>

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