eth-signature-mark

Generates a visual marker which can be embedded in a PNG image and then later translated into an Ethereum signature. The purpose of this library is to provide a simple way of adding an Ethereum signature to PNG files (for example, NFTs) so that identity information can be encoded directly in an image even if that image were to be downloaded.

Sample

Generated by the following call: await drawSignatureMark('./sample.png', '0x21fbf0696d5e0aa2ef41a2b4ffb623bcaf070461d61cf7251c74161f82fec3a4370854bc0a34b3ab487c1bc021cd318c734c51ae29374f2beb0e6f2dd49b4bf41c', 0, 0, 100, 100);

Installation

# as a command-line tool
npm install eth-signature-mark -g

# as a library
npm install eth-signature-mark --save

Usage

CLI

# an Ethereum signature:
SIG='0x21fbf0696d5e0aa2ef41a2b4ffb623bcaf070461d61cf7251c74161f82fec3a4370854bc0a34b3ab487c1bc021cd318c734c51ae29374f2beb0e6f2dd49b4bf41c'

# get version
eth-signature-mark -v

# create a signature mark on a new image (250x250)
eth-signature-mark --create './newImage.png' $SIG 0,0,50,50

# create a signature mark on an existing image (30x30)
eth-signature-mark --create './existingImage.png' $SIG

# extract a signature mark from an image
eth-signature-mark --extract './newImage.png' 0,0,50,50

# extract a signature mark from an image
eth-signature-mark --extract './existingImage.png'

NodeJS Library

const { drawSignatureMark, extractSignatureMark } = require('eth-signature-mark');

// an Ethereum signature:
const sig = '0x21fbf0696d5e0aa2ef41a2b4ffb623bcaf070461d61cf7251c74161f82fec3a4370854bc0a34b3ab487c1bc021cd318c734c51ae29374f2beb0e6f2dd49b4bf41c';

// write a new PNG file (new file will be 500x500 in size):
await drawSignatureMark('newImage.png' sig, 0, 0, 100, 100);)

// write a signature mark on an existing file:
// defaults to 6px by 6px cells starting at position (6, 6)
await drawSignatureMark('existingImage.png', sig);

// extract signature data from an existing image (also accepts x, y, width, height parameters).
const checkSig = await extractSignatureMark('existingImage.png');

assert.ok(sig === checkSig);