jSignature jQuery plugin - make an image from signature stored in DB (base30)

Question

After we save the image with this command

$("#canvas").jSignature("getData", "base30");

we can store that data to DB and it is a simple string:

data:image/jsignature;base30,9MZ4555665655465644644645433232100Y2333465656786456646464443Z54334433222Y13344544486666667775353646443_2xZ110000000Y1111111222223222344555332220100000Z11111121212130Y122222333343222111100000Z1111212222122212

And now how to make an image from "base30" signature? Can we convert this to anything so it can be displayed on the website?

Or maybe there is a way to disable editing the canvas. To prevent changing the signature?

UPDATE

I have made a little workaround and it works.

I have created an invisible div where i load the jSignature from DB and made it invisible, then i get the svg out of it and display that svg in the page

<div id="oldSignature" style="display: none"></div>
<object id="img" type="image/svg+xml" data="">
    Your browser doesn't support SVG!
</object>

@if (isset($offer->signature))
        var sigCanvas = $("#oldSignature").jSignature({width: 700, height: 180, "background-color":"#ddd"});
        $("#oldSignature").jSignature("importData", "{{$offer->signature}}");
        var svg = $("#oldSignature").jSignature("getData", "svg");
        $("#img").attr("data", 'data:' + svg);
@endif

Answer 1

Look in the extras folder on Github. There are php and DotNet examples.

Regarding the Base30 format, the docs for jSignature say

base30 (alias image/jSignature;base30) (EXPORT AND IMPORT) (VECTOR) data format is a Base64-spirited compression format tuned for absurd compactness and native url-compatibility. It is "native" data structure compressed into a compact string representation of all vectors. Code examples (.Net, Python) detailing decompression of this format into render-able form (SVG, language-native coordinate arrays) are provided in the extras folder. One of possible ways of communicating the data to the server is JSONP, which has a practical URL length limit (imposed by IE, of course) of no more than 2000+ characters. This compression format is natively URL-compatible without a need for re-encoding, yet will fit into 2000 characters for most non-complex signatures.

Edit - for those not having success with the /extras example, there may be some useful help / sample code here in this case at Github related to Convert Base30 to PNG using PhP . Too much detail there to include here.

Answer 2

I used the above answer and changed a little bit in the function to get the following. This worked for me.

<?php
ini_set ( 'display_errors', E_ALL );
require_once ('jSignature_Tools_Base30.php');

function base30_to_jpeg($base30_string, $output_file) {
$data = str_replace ( 'image/jsignature;base30,', '', $base30_string );
$converter = new jSignature_Tools_Base30 ();
$raw = $converter->Base64ToNative ( $data );
// Calculate dimensions
$width = 0;
$height = 0;
foreach ( $raw as $line ) {
    if (max ( $line ['x'] ) > $width)
        $width = max ( $line ['x'] );
    if (max ( $line ['y'] ) > $height)
        $height = max ( $line ['y'] );
}

// Create an image
$im = imagecreatetruecolor ( $width + 20, $height + 20 );

// Save transparency for PNG
imagesavealpha ( $im, true );
// Fill background with transparency
$trans_colour = imagecolorallocatealpha ( $im, 255, 255, 255, 127 );
imagefill ( $im, 0, 0, $trans_colour );
// Set pen thickness
imagesetthickness ( $im, 2 );
// Set pen color to black
$black = imagecolorallocate ( $im, 0, 0, 0 );
// Loop through array pairs from each signature word
for($i = 0; $i < count ( $raw ); $i ++) {
    // Loop through each pair in a word
    for($j = 0; $j < count ( $raw [$i] ['x'] ); $j ++) {
        // Make sure we are not on the last coordinate in the array
        if (! isset ( $raw [$i] ['x'] [$j] ))
            break;
        if (! isset ( $raw [$i] ['x'] [$j + 1] ))
            // Draw the dot for the coordinate
            imagesetpixel ( $im, $raw [$i] ['x'] [$j], $raw [$i] ['y'] [$j], $black );
        else
            // Draw the line for the coordinate pair
            imageline ( $im, $raw [$i] ['x'] [$j], $raw [$i] ['y'] [$j], $raw [$i] ['x'] [$j + 1], $raw [$i] ['y'] [$j + 1], $black );
    }
}

// Check if the image exists
if (! file_exists ( dirname ( $output_file ) )) {
    mkdir(dirname($output_file));
}

// Create Image
$ifp = fopen ( $output_file, "wb" );
imagepng ( $im, $output_file );
fclose ( $ifp );
imagedestroy ( $im );

return $output_file;
}

// test
$imgStr ='image/jsignature;base30,7U010100010000000001_1G88b8ace99aab756856_bE2000000010000000101_1D6689cbaa9b956558564_8w757698987766566556545_3PZ2110101010100000000Y10_fF0000Z2100001000Y110_1V9789cb86966655475_fK_1x';
base30_to_jpeg ( $imgStr, 'test.png' );

?>