photomask v0.1.4

Apply an alpha mask to your text using SVG and CSS with custom font support and fine-tuning.

• npm: npm install photomask --save

Tested with Chrome 46.0, Opera 33.0, Firefox 42.0 and Safari 9.0.1.

Getting Started

Photomask provides a x-photomask element that uses HTML5 custom elements to extend the HTMLImageElement.prototype object.

<img is="x-photomask" src="path/to/landscape.png" alt="Photomask" />

Note: For the image the src attribute will be used, and the text will be taken from the img element's alt attribute. When creating the img element, you're required to add the is="x-photomask" attribute which is a registered custom element.

Once you have inserted your img[is="x-photomask"] element into the DOM, Photomask will apply the mask automatically for you.

Fine-tuning via Padding

Photomask attempts to recursively compute the ideal font size for your supplied text using canvas' measureText method – yet some fonts are not computed perfectly. For these instances Photomask allows you to style your img element using the standard padding property via CSS to adjust for imperfections.

Padding will be applied as a buffer around the image allowing all of the text to fit snuggly inside the container. Likewise if you wish to add a little padding on the top to correct the vertical positioning, padding-top is also recognised to allow the text to be positioned perfectly.

img[is="x-photomask"] {
    padding: 4px 15px 0 15px;
}

Using Custom Fonts

By supplying the font-family property you can change the font. Adding a custom font is achieved via the registerFont function — you must pass the name (font-family) of the font and the dataUri which you can generate via Dopiaza.

import {registerFont} from 'photomask';

// ...

registerFont('Pacifico', 'data:application/font-woff;base64,d09GRk...');

Adjusting Background

In some cases you may wish to adjust the background to allow a different segment of the background to shine through — the fine-tuning for the background can be done using the background-position property.

img[is="x-photomask"] {
    background-position: 100px 50px;
}

Manual Rendering

Photomask uses the transform function to provide the rendering of the text with a mask applied.

import {transform} from 'photomask';

// ...

const imgElement = document.querySelector('img');
transform(imgElement, { text: 'Photomask', image: 'path/to/image.png' });

Note: When using the custom element approach, the values are taken directly from the element — with the src and alt attributes – however when you invoke transform manually, you need to pass the image and text to the function as the second argument.

However Photomask always conveniently exports the readAttributes function, so you can use that to pass in to the transform function.

import {transform, readAttributes} from 'photomask';

// ...

const imgElement = document.querySelector('img');
transform(imgElement, readAttributes(imgElement));