Jimp

The "JavaScript Image Manipulation Program" :-)

An image processing library written entirely in JavaScript for Node, with zero external or native dependencies.

Example usage:

var Jimp = require("jimp");

// open a file called "lenna.png"
var lenna = new Jimp("lenna.png", function () {
    this.resize(220, 220) // resize
        .write("lenna-small.png") // save
        .quality(60) // set JPEG quality
        .write("lenna-small.jpg") // save as JPEG
        .greyscale() // set greyscale
        .write("lena-small-bw.png") // save again
        .crop(80, 100, 80, 50) // crop
        .write("lena-small-bw-cropped.png"); // save again
});

Methods

The Jimp constructor takes two arugments, the path to a JPEG or PNG image and an optional call back for when the image is parsed:

var image = new Jimp("./path/to/image.jpg", function () {
    // ready
});

Once the callback has fired the following methods can be called on the image:

image.crop( x, y, w, h ); // crop to the given region
image.invert(); // invert the image colours
image.greyscale(); // remove colour from the image
image.sepia(); // apply a sepia wash to the image
image.opacity( f ); // apply an opacity of 0-1 to the image
image.resize( w, h ); // resize the image
image.scale( f ); // scale the image by the factor f
image.blur( r ); // fast blur the image by r pixels
image.gaussian( r ); // Gaussian blur the image by r pixels (VERY slow)

(Contributions of more methods are welcome!)

The image can be written to disk in JPEG or PNG format using:

image.write( path, cb ); // callback will be fired when write is successful

The quality of saved JPEGs can be set with:

image.quality( n ); // set the quality of saved JPEG, 0 - 100

Advanced

The library enables low-level manipulation of images in memory through the bitmap property of each Jimp object:

image.bitmap.data; // a buffer of the raw bitmap data
image.bitmap.width; // the width of the image
image.bitmap.height // the height of the image

This can be manipulated directory, but remember: garbage in, garbage out.

A helper method is available to scan a region of the bitmap:

image.scan(x, y, w, h, cb); // scan a given region of the bitmap and call cb on every pixel

Example usage:

image.scan(0, 0, image.bitmap.width, image.bitmap.height, function (x, y, idx) {
    // x, y is the position of this pixel on the image
    // idx is the position start position of this rgba tuple in the bitmap buffer
    
    var red = this.bitmap.data[idx];
    var green = this.bitmap.data[idx+1];
    var blue = this.bitmap.data[idx+2];
    var alpha = this.bitmap.data[idx+3];
    
    // rgba values run from 0 - 255
    // e.g. this.bitmap.data[idx] = 0; // removes red from this pixel
});

License

Jimp is licensed under the MIT license.