blanda

Image blending functions à la Photoshop's layer blend modes.

Usage

var blanda = require("blanda");

var blendedImage = blanda.multiply(imageA, imageB);

The following blend functions are available:

• colorburn()
• colordodge()
• darken()
• darkercolor()
• difference()
• divide()
• exclusion()
• hardlight()
• hardmix()
• lighten()
• lightercolor()
• linearburn()
• lineardodge()
• linearlight()
• multiply()
• overlay()
• pinlight()
• screen()
• softlight()
• subtract()
• vividlight()

All blend functions take two parameters, imageA and imageB, each being an object with the following properties:

• width - The width of the image
• height - The height of the image
• data - An array of (width * height * 4) RGBA pixel values. Any array type (or Node Buffer object) should do but values should be in the range [0,255]

This format is compatible with e.g. ImageData objects created by <canvas> elements, as well as those used by e.g. pngjs.

All blend functions return image data objects with similar structure (using an Uint8Array to hold pixel values).

Example with pngjs

var blanda = require("blanda");
var PNG = require("pngjs").PNG;

// read PNG image data with pngjs
function getImageData(src, callback) {
    fs.createReadStream(src).pipe(
        new PNG({filterType: 4})
    ).on("parsed", function() {
        callback(this);
    });
}

// write PNG image data with pngjs
function writeImageData(dst, imageData, callback) {
    var png = new PNG({
        filterType: 4,
        width: imageData.width,
        height: imageData.height,
        depth: 8
    });
    png.data = new Buffer(imageData.data);
    png.pack().pipe(fs.createWriteStream(dst)).on("finish", callback);
}


getImageData("A.png", function(imageA) {
    getImageData("B.png", function(imageB) {
        var blendedImage = blanda.linearburn(imageA, imageB);
        writeImageData("out.png", blendedImage, () => {
            callback();
        });
    });
});