@jakubdolejs/image_utils

Image utilities for Node

This library is a collection of image manipulation utilities running inside the Node JS runtime. The manipulation is done using ImageMagick.

Requirements

• NodeJS
• ImageMagick

Installation

npm install @jakubdolejs/image_utils

Usage

Get image dimensions

import { Size, imageSize } from "@jakubdolejs/image_utils"
import fs from "fs"

const file = "myimage.png"
fs.promises.readFile(file)
    .then(image => imageSize(image))
    .then(size => console.log(`The dimensions of ${file} are ${size.width} x ${size.height} pixels`))
    .catch(error => console.error(error))

Convert image to a different format*

The following script converts an image called myimage.png to a JPG image called myimage.jpg

import { convert } from "@jakubdolejs/image_utils"
import fs from "fs"

const file = "myimage.png"
const jpegFile = "myimage.jpg"
fs.promises.readFile(file)
    .then(image => convert(image, "jpg"))
    .then(jpeg => fs.promises.writeFile(jpegFile))
    .catch(error => console.error(error))

*Supported formats are PNG and JPG

Crop image

The following script crops an image called myimage.png to a 200 × 300 pixel rectangle that starts 10 pixels from the left edge of the image and 20 pixels from the top of the image. The script then writes the cropped image to a file called mycroppedimage.png.

import { crop } from "@jakubdolejs/image_utils"
import fs from "fs"

const file = "myimage.png"
const croppedImageFile = "mycroppedimage.png"
const x = 10
const y = 20
const width = 200
const height = 300
fs.promises.readFile(file)
    .then(image => crop(image, x, y, width, height))
    .then(croppedImage => fs.promises.writeFile(croppedImageFile, croppedImage))
    .catch(error => console.error(error))

Resample image

The following script resamples an image called myimage.png to fit into a rectangle that's 200 pixels wide and 300 pixels tall. The script then writes the cropped image to a file called myresampledimage.png.

import { resample } from "@jakubdolejs/image_utils"
import fs from "fs"

const file = "myimage.png"
const resampledImageFile = "myresampledimage.png"
const width = 200
const height = 300
fs.promises.readFile(file)
    .then(image => resample(image, width, height))
    .then(resampledImage => fs.promises.writeFile(resampledImageFile, resampledImage)
    .catch(error => console.error(error))

Stack images

The following script stacks the image called top.png on top of image called bottom.png. If the images are different widths they will be centered. The script writes the resulting image in a file called myverticalstack.png.

To stack images horizontally substitute stackVertically with stackHorizontally.

import { stackVertically } from "@jakubdolejs/image_utils"
import fs from "fs"

const top = "top.png"
const bottom = "bottom.png"
const stackedImages = "myverticalstack.png"
fs.promises.readFile(top)
    .then(topImage => {
        return fs.promises.readFile(bottom)
            .then(bottomImage => stackVertically([topImage, bottomImage], "Center", "png")
    })
    .then(stackedImage => fs.promises.writeFile(stackedImages, stackedImage))
    .catch(error => console.error(error))

Draw a rectangle on image

The following script draws a rectangle with 4-pixel wide green stroke and semi-transparent fill 10 pixels from each edge of a 640 × 480 pixel image called myimage.png. The script writes the resulting image in a file called myimagewithrectangle.png.

import { drawRectangle, Colour } from "@jakubdolejs/image_utils"
import fs from "fs"

const file = "myimage.png"
const fileWithRectangle = "myimagewithrectangle.png"
const rectangle = {
    "x": 10,
    "y": 10,
    "width": 620,
    "height": 460
}
const fillColour = Colour.TRANSPARENT
const stroke = {
    "width": 4,
    "colour": Colour.GREEN
}
fs.promises.readFile(file)
    .then(image => drawRectangle(image, rectangle, fillColour, stroke, "png"))
    .then(imageWithRectangle => fs.promises.writeFile(fileWithRectangle, imageWithRectangle))
    .catch(error => console.error(error))