Blur Up

A tool that creates a small, optimized version of an input image and embeds it in an SVG file. The generated SVG file scales the integrated image up to its original dimensions and applies a blur filter to create a high quality preview of the original image. Such preview SVGs can be used as temporary substitutes for images that take longer to load.

| Preview SVG | Original Image | |-------------|------------------| | 1086 Bytes | 402.15 Kilobytes | | | |

Installation

npm install svg-blur-up

Usage

Command Line Interface (CLI)

The command line tool can be invoked using the blur-up command:

blur-up -i images/* -o previews -c configs/blur-up.json

You may provide a configuration via package.json or as a standalone file. If there is no configuration in package.json, the tool will look for a configuration file with the default name .blur-up.json in the current working directory. Please refer to the Options section for more information.

| Option | Shorthand | Description | |----------------|-----------|--------------------------------------------| | --input | -i | Specifies the input path or glob pattern | | --output | -o | Specifies the output directory | | --config | -c | Specifies an alternative config path |

JavaScript API

The blurUp function returns a Promise.

import blurUp from "svg-blur-up";

// The input path must describe a single file.
blurUp("images/bg.jpg", "output/dir", options)
  .catch((e) => console.error(e));

Output

Each individual image will be wrapped in an SVG construct of the following form:

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"
  width="IMG_WIDTH" height="IMG_HEIGHT" viewBox="0 0 VIEW_WIDTH VIEW_HEIGHT" preserveAspectRatio="none">
  <filter id="blur" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
    <feGaussianBlur stdDeviation="STD_DEVIATION_X STD_DEVIATION_Y" edgeMode="duplicate" />
    <feComponentTransfer><feFuncA type="discrete" tableValues="1 1" /></feComponentTransfer>
  </filter>
  <image filter="url(#blur)" x="0" y="0" height="100%" width="100%" xlink:href="IMG_DATA_URI" />
</svg>

Note: The generated SVG file will be minified.

Options

| Option | Default | Description | |---------------|----------|--------------------------------------------| | input | - | Can be a single path or an array of paths | | output | - | A path that describes a file or directory | | stdDeviationX | 20 | The blur strength along the X-axis | | stdDeviationY | 20 | The blur strength along the Y-axis | | width | auto, 40 | The width of the preview image | | height | auto | The height of the preview image |

The command line options --input and --output overwrite the respective fields in the configuration.

If only width or height is specified, the counter part will be calculated automatically to preserve the original aspect ratio. If both of these fields are undefined, width will be set to 40 and height will be adjusted accordingly.

.blur-up.json

{
  "input": "images/*.{bmp,jpg,png}",
  "output": "images/previews",
  "stdDeviationX": 10,
  "stdDeviationY": 10,
  "width": 30
}

package.json

{
  "blurUp": {
    "input": ["path/to/img/*.jpg", "other/path/*.png"],
    "output": "output/dir"
  }
}

blur-up.js

import blurUp from "svg-blur-up";

blurUp("path/to/img.jpg", "output/dir", {
  stdDeviationX: 5,
  stdDeviationY: 5
}).catch((e) => console.error(e));

Contributing

Maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code.