text-to-image
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5.2.0 • Public • Published

Text to image

Code Coverage Npm Version License

A library for generating an image data URI representing an image containing the text of your choice.

Originally part of a Twitter bot for publishing tweets longer than 140 characters, the generator takes a string and an optional configuration object as parameters and produces an image data URI (data:image/png;base64,iVBORw0KGgoAAAA...).

Try it

Use this CodeSandbox to try out text-to-image in your browser.

Installation

npm i text-to-image

Note that text-to-image uses node-canvas to generate the images. For text-to-image to install, you might have to fulfill the installation requirements for node-canvas. Please refer to their documentation for instructions.

Usage

const textToImage = require('text-to-image');

// using the asynchronous API with await
const dataUri = await textToImage.generate('Lorem ipsum dolor sit amet');

// using the asynchronous API with .then
textToImage.generate('Lorem ipsum dolor sit amet').then(function (dataUri) {
  // use the dataUri
});

// using the synchronous API
const dataUri = textToImage.generateSync('Lorem ipsum dolor sit amet');

This is an example of a full dataUri generated by the above examples:

data:image/png;base64,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

Copy that line into the address field of your browser and you should see the generated image.

With the default options the image generator will adjust the height of the image automatically to fit all text, while the width of the image is fixed to the specified width.

Text formatting rules

Normal spaces are stripped from the beginning of paragraphs. To add leading spaces, either use tab or non-breaking space characters.

Line breaks can be added with \n.

Example:

const textToImage = require('text-to-image');

// Add indent as tabs
const tabbedText = await textToImage.generate(
  '\tDonec id elit non mi porta gravida at eget metus. \n\tSed posuere consectetur est at lobortis.',
);

// Add indent as non-breaking spaces
const spacedText = await textToImage.generate(
  '\xA0\xA0Donec id elit non mi porta gravida at eget metus. \n\xA0\xA0Sed posuere consectetur est at lobortis.',
);

Configuring

The generate and generateSync functions take an optional second parameter containing configuration options for the image. All configuraion parameters are optional.

Note that the supplied configuration values are not validated. Invalid values may lead to unexpected results or the image not getting generated at all. For color value validations, consider using a library like validate-color before passing the value to this library.

The available options are as follows.

Name Type Default value Description
bgColor string | CanvasGradient | CanvasPattern #FFFFFF Sets the background color of the image. See CanvasRenderingContext2D.fillStyle for valid values, or use a color value validator (see note above).
bubbleTail { width: number; height: number } { width: 0, height: 0 } Renders a speech bubble tail with the specified size at the bottom center of the image.
customHeight number 0 Sets the height of the generated image in pixels. If falsy, will automatically calculate the height based on the amount of text.
debug boolean false Set to true to turn on debug mode (see below).
debugFilename string timestamp Set a custom file name (may include a custom path) for the file created in debug mode. Defaults to a timestamp with a .png extension in the current working directory.
fontFamily string Helvetica The font family to use for the text in the image. See CSS font-family for valid values.
fontPath string The file system path to a font file to use, also specify fontFamily if you use this.
fontSize number 18 The font size to use for the text in the image. See CSS font-size for valid values.
fontWeight string | number normal The font weight to use for the text in the image. See CSS font-weight for valid values.
lineHeight number 28 The line height for the generated text.
margin number 10 The margin (all sides) between the text and the border of the image.
maxWidth number 400 Sets the width of the generated image in pixels.
textAlign string left The text alignment for the generated text. See CanvasRenderingContext2D.textAlign for valid values.
textColor string #000000 Sets the text color. See CanvasRenderingContext2D.fillStyle for valid values, or use a color value validator (see note above).
verticalAlign string top Use to set center height with customHeight (possible values: top, center).

Example:

const textToImage = require('text-to-image');

const dataUri = await textToImage.generate('Lorem ipsum dolor sit amet', {
  debug: true,
  maxWidth: 720,
  fontSize: 18,
  fontFamily: 'Arial',
  lineHeight: 30,
  margin: 5,
  bgColor: 'blue',
  textColor: 'red',
});

Debugging

Turn on debug mode to have the library store the generated image data URI as a PNG in the current working directory (where the process was started). The image name will be the current date and time. For more control over the debug file name and location, specify the debugFilename option, which can include path segments in addition to the file name. A relative paths (or only a file name without path) will be resolved starting from the current working directory. Any missing parent directories to the file will be created as needed.

Example:

const textToImage = require('text-to-image');
const path = require('path');

const dataUri = await textToImage.generate('Lorem ipsum dolor sit amet', {
  debug: true,
  debugFilename: path.join('some', 'custom', 'path', 'to', 'debug_file.png'),
});

This will create the debug file some/custom/path/to/debug_file.png in the current working directory.

Test

The library is tested using Jest. Run the test suit by executing

npm test

A coverage report will be generated in coverage/.

Contributing

Pull requests are welcome. Read the Contributing guidelines.

License

ISC License (ISC)

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