documentation.md

Signature to Image Documentation

A supplemental script for Signature Pad that generates an image of the signature’s JSON output server-side using PHP.

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• Introduction
• How-to
  • How-to: Step-by-Step
• Function Reference
• Options
  • Options Reference
• Version History
• License
• Other Solutions

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Introduction

Signature to Image is a simple PHP script that will take the JSON output of Signature Pad and generate an image file server-side to be saved for later. Uses the GD Image Library for image generation and PHP’s built in json_decode() if a string is passed.

How-to

The whole signature to image generation requires just a few lines of PHP:

<?php
require_once 'signature-to-image.php';

$json = $_POST['output'];
$img = sigJsonToImage($json);

imagepng($img, 'signature.png');
imagedestroy($img);

How-to: Step-by-Step

First, include the required PHP file: signature-to-image.php.

<?php
require_once 'signature-to-image.php';

Get the signature from the form post. Signature Pad defaults to naming the post field as output.

<?php
$json = $_POST['output'];

Then, call the function, passing a string representing the JSON, submitted by Signature Pad, or an already decoded JSON object (using json_decode()).

<?php
$img = sigJsonToImage($json);

The $img variable will be an image resource, which you can either display immediately or save to a file.

Save to file

<?php
imagepng($img, 'signature.png');

Display in the browser

<?php
header('Content-Type: image/png');
imagepng($img);

Cleanup

When you have finished with the image resource, make sure to clean up after yourself and free some memory.

<?php
imagedestroy($img);

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Function Reference

Method	Arguments	Return	Description
sigJsonToImage( $json, $options)	$json:json|string String or decoded JSON representing the signature output $options:array Array of properties to change the default options	image resource	Redraws the signature as a GD Library image resource

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Options

Options can be passed as the second argument of the function when called. Only options that are different from the defaults need to be included in the options array.

<?php
$img = sigJsonToImage($json, array('imageSize'=>array(198, 55)));

It’s highly recommended that the options used server-side match the values used in the Javascript.

Options Reference

Name	Type	Default Value	Description
imageSize	array width, height	array(198, 55)	Determines the final output size of the image
bgColour	array hex red, hex green, hex blue string transparent	array(0xff, 0xff, 0xff)	The colour fill for the background of the image Transparency: array('bgColour' => 'transparent')
penWidth	int	2	Thickness, in pixels, of the drawing pen
penColour	array hex red, hex green, hex blue	array(0x14, 0x53, 0x94)	Colour of the drawing ink
drawMultiplier	int	12	The signature is enlarged by this factor before being redrawn to maintain a smooth finish. Reduce this only if you are having memory issues.

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Version History

Check out the changelog on GitHub.

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License

Signature to Image is licensed under the New BSD license, which is included in the downloadable package.

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Other Solutions

• PHP to SVG: sigToSvg by Charles Gebhard is a script for converting the signature JSON to SVG using PHP. Check out the amazing sigToSvg on GitHub.
• Python: python-signpad2image by Alan Viars is a script for converting the signature JSON to PNG using Python. Check out the fantastico python-signpad2image on GitHub.
• Ruby on Rails: ruby-signaturepad-to-image.rb by Phil Hofmann is a chunk of code for converting signature JSON to PNG within a Ruby on Rails app. Check out the wam-bham ruby-signaturepad-to-image.rb on Github.
• C#: SignatureToDotNet by Curtis Herbert is a script for converting the signature JSON to an image using C#. Check out the awesome SignatureToDotNet project on GitHub.
• Perl: signature-to-image.pl by Jim Turner is a script for converting the signature JSON to a PNG using Perl. Check out the fabulous signature-to-image.pl on CPAN.
• ColdFusion: sigJsonToImage by James Moberg is a script for converting the signature JSON to an PNG using ColdFusion. Check out the super-duper sigJsonToImage project on CFLib.org.
• Java: SignatureToImageJava by Vinod Kiran is a script for converting the signature JSON to an image using Java. Check out the rad SignatureToImageJava project on GitHub.