imagecache-sharp

What is it?

Imagecache Sharp is a node image processing module based on sharp that allows you to create presets based on a list of chained actions, such as resizing, applying a watermark, or applying various image operations (blur, flip, negate, etc).

It was inspired by Drupal's image styles (hence the name).

Installation

• npm install imagecache-sharp

Usage

import { ImageCache, Image } from "../src/imagecache";
import presets from "./presets";

const imagecache: ImageCache = new ImageCache(presets);

const image: Image = await imagecache.render(
  "./in.png",
  "canvas_scale_with_blur"
);

// Save the image
await image.toFile("out_canvas_scale_with_blur.png");

// Get a buffer, stream it etc
image.toBuffer(...)

The render function returns a sharp.Sharp instance (Image is just an alias for it) which can be used in various ways for outputting the final image. For a list of options see sharp's documentation.

Presets structure

A preset is defined like this:

type Preset = {
  presetName: string;
  actions: Action[];
};

An action contains an operation (which is defined by the plugins) and an optional config.

type Action = {
  action: string;
  config?: any;
};

Here are two example presets. The first one resizes and crops the image, puts it on a bigger canvas, then blurs it. The second one resizes and crops the image.

export default [
  {
    presetName: 'canvas_scale_with_blur',
    actions: [
      {
        action: 'scale_and_crop',
        config: {
          width: 152,
          height: 152,
        },
      },
      {
        action: 'define_canvas',
        config: {
          color: '#333333',
          width: 400,
          height: 400,
        },
      },
      {
        action: 'blur',
      },
    ],
  },
  {
    presetName: 'scale_crop_tiny',
    actions: [
      {
        action: 'scale_and_crop',
        config: {
          width: 32,
          height: 32,
        },
      },
    ],
  },
];

Imagecache actions:

Blur

Blurs the image.

Action name: blur.

Configuration:

• sigma: A value between 0.3 and 1000 representing the sigma of the Gaussian mask. Defaults to 50.

Define canvas

Defines a new canvas and overlays the current image.

Action name: define_canvas.

Configuration:

• width: The width of the canvas.
• height: The height of the canvas.
• channels: Number of channels. Defaults to 4.
• background: The background colour of the canvas in hex format.

File

Loads an image and overlays it on the current image.

Action name: file.

Configuration:

• path: The path of the file.
• gravity: Gravity at which to place the overlay. Possible values are north, northeast, east, southeast, south, southwest, west, northwest, center and centre. Defaults to center.
• tile: Set to true to repeat the overlay image across the entire image with the given gravity. Defaults to false.

Flip

Flips the image on a given axis.

Action name: flip.

Configuration:

• axis: The axis to flip on. Defaults to y.

Gamma

Apply a gamma correction to the image.

Action name: gamma.

Configuration:

• gamma: Value between 1.0 and 3.0. Defaults to 2.2.

Greyscale

Convert to 8-bit greyscale, 256 shades of grey.

Action name: greyscale.

Negate

Produce the "negative" of the image.

Action name: negate.

Normalize

Enhance output image contrast by stretching its luminance to cover the full dynamic range.

Action name: normalize.

Rotate

Rotates the image based on the EXIF data or at a specified angle.

Action name: rotate.

Configuration:

• angle: Angle, multiple of 90. Defaults to auto which uses EXIF.

Scale

Scales the image ignoring the aspect ratio.

Action name: scale.

Configuration:

• width: The width of the new image. Can be a number or a percent value.
• height: The height of the new image. Can be a number or a percent value.
• upscale: Whether to upscale the image. Defaults to true.

Scale and crop

Scales and crops the image maintaining the aspect ratio.

Action name: scale_and_crop.

Configuration:

• width: The width of the new image. Can be a number or a percent value.
• height: The height of the new image. Can be a number or a percent value.
• gravity: Where to crop from. Possible values are north, northeast, east, southeast, south, southwest, west, northwest, center and centre. Defaults to center.

Sharpen

Sharpen the image.

Action name: sharpen.

Configuration:

• sigma: The sigma of the Gaussian mask. Defaults to 1.
• flat: The level of sharpening to apply to "flat" areas. Defaults to 1.0.
• jagged: The level of sharpening to apply to "jagged" areas. Defaults to 2.0.

Thanks to:

• Smashicons - Flaticon for the logo.