php - How to display a JSON/base64 encoded image in FPDF?

Question

I'm storing signatures (using signaturepad in my database Coldfusion/MySQL 5.0.88 and would like to output the signature I'm taking onto a pdf which I'm generating with fpdf. However I can*t get it to work...

Signatures are stored like this:

[{"lx":19,"ly":58,"mx":19,"my":57},{"lx":23,"ly":54,"mx":19,"my":58},{"lx":26,"ly":53,"mx":23,"my":54},{"lx":32,"ly":51,"mx":26,"my":53},{"lx":38,"ly":47,"mx":32,"my":51},{"lx":44,"ly":44,"mx":38,"my":47},{"lx":51,"ly":41,"mx":44,"my":44},{"lx":58,"ly":37,"mx":51,"my":41},{"lx":64,"ly":35,"mx":58,"my":37},{"lx":67,"ly":31,"mx":64,"my":35},{"lx":70,"ly":30,"mx":67,"my":31},{"lx":72,"ly":28,"mx":70,"my":30},{"lx":71,"ly":28,"mx":72,"my":28},{"lx":69,"ly":28,"mx":71,"my":28},{"lx":66,"ly":28,"mx":69,"my":28},{"lx":62,"ly":29,"mx":66,"my":28},{"lx":59,"ly":31,"mx":62,"my":29},{"lx":55,"ly":32,"mx":59,"my":31},{"lx":52,"ly":33,"mx":55,"my":32},{"lx":48,"ly":35,"mx":52,"my":33},{"lx":44,"ly":37,"mx":48,"my":35},{"lx":41,"ly":38,"mx":44,"my":37},{"lx":39,"ly":40,"mx":41,"my":38},{"lx":36,"ly":40,"mx":39,"my":40},{"lx":33,"ly":42,"mx":36,"my":40},{"lx":32,"ly":43,"mx":33,"my":42},{"lx":31,"ly":44,"mx":32,"my":43},{"lx":31,"ly":46,"mx":31,"my":44},{"lx":32,"ly":48,"mx":31,"my":46},{"lx":136,"ly":23,"mx":32,"my":48},{"lx":132,"ly":24,"mx":136,"my":23},{"lx":104,"ly":38,"mx":132,"my":24},{"lx":103,"ly":40,"mx":104,"my":38},{"lx":102,"ly":41,"mx":103,"my":40},{"lx":102,"ly":42,"mx":102,"my":41},{"lx":103,"ly":42,"mx":102,"my":42},{"lx":108,"ly":42,"mx":103,"my":42},{"lx":115,"ly":42,"mx":108,"my":42},{"lx":123,"ly":39,"mx":115,"my":42},{"lx":133,"ly":36,"mx":123,"my":39},{"lx":141,"ly":34,"mx":133,"my":36},{"lx":148,"ly":32,"mx":141,"my":34},{"lx":155,"ly":30,"mx":148,"my":32},{"lx":159,"ly":29,"mx":155,"my":30},{"lx":161,"ly":28,"mx":159,"my":29},{"lx":159,"ly":27,"mx":161,"my":28},{"lx":155,"ly":27,"mx":159,"my":27},{"lx":151,"ly":27,"mx":155,"my":27},{"lx":145,"ly":27,"mx":151,"my":27},{"lx":140,"ly":29,"mx":145,"my":27},{"lx":135,"ly":31,"mx":140,"my":29},{"lx":132,"ly":33,"mx":135,"my":31},{"lx":127,"ly":36,"mx":132,"my":33},{"lx":125,"ly":38,"mx":127,"my":36},{"lx":125,"ly":40,"mx":125,"my":38},{"lx":125,"ly":41,"mx":125,"my":40},{"lx":125,"ly":42,"mx":125,"my":41},{"lx":127,"ly":43,"mx":125,"my":42},{"lx":131,"ly":44,"mx":127,"my":43},{"lx":139,"ly":45,"mx":131,"my":44},{"lx":147,"ly":45,"mx":139,"my":45},{"lx":157,"ly":43,"mx":147,"my":45},{"lx":164,"ly":41,"mx":157,"my":43},{"lx":173,"ly":39,"mx":164,"my":41},{"lx":181,"ly":36,"mx":173,"my":39},{"lx":186,"ly":34,"mx":181,"my":36},{"lx":191,"ly":33,"mx":186,"my":34},{"lx":193,"ly":30,"mx":191,"my":33},{"lx":194,"ly":29,"mx":193,"my":30},{"lx":194,"ly":28,"mx":194,"my":29},{"lx":193,"ly":27,"mx":194,"my":28},{"lx":191,"ly":26,"mx":193,"my":27},{"lx":188,"ly":25,"mx":191,"my":26},{"lx":183,"ly":25,"mx":188,"my":25},{"lx":180,"ly":25,"mx":183,"my":25},{"lx":177,"ly":25,"mx":180,"my":25},{"lx":174,"ly":27,"mx":177,"my":25},{"lx":171,"ly":30,"mx":174,"my":27},{"lx":169,"ly":32,"mx":171,"my":30},{"lx":168,"ly":34,"mx":169,"my":32},{"lx":167,"ly":36,"mx":168,"my":34},{"lx":167,"ly":38,"mx":167,"my":36},{"lx":168,"ly":40,"mx":167,"my":38},{"lx":169,"ly":41,"mx":168,"my":40},{"lx":171,"ly":41,"mx":169,"my":41},{"lx":174,"ly":41,"mx":171,"my":41},{"lx":176,"ly":41,"mx":174,"my":41},{"lx":176,"ly":40,"mx":176,"my":41},{"lx":177,"ly":39,"mx":176,"my":40},{"lx":177,"ly":37,"mx":177,"my":39}]

There is a custom function included in siganturepad (signature to image) to convert the above back into an image. Like so:

<?php
require_once '../../signature-to-image.php';
$img = sigJsonToImage(file_get_contents('sig-output.json'));

// Output to browser
header('Content-Type: image/png');
imagepng($img);

imagedestroy($img);
>

But if I try this on my fpdf page, the whole page breaks ( I guess because I want to embed the image in a cell not output only the image to the browser) and I get this:

Resource id #10‰PNG IHDR?7?7￠?±IDATx?í?iP[×?/’a6±￡'?àk0??Y?6)Nò?‰Y?μM2?′nf:“d2gq“?u?q–Ió! ?Sa?NJgR?? ’@1KOFf±?′ àf??/}y‘?`?t>x???Go?{?=?…1.Pm? €ük@IA(J B1PR?’?P”?b ¤ %?()?@IA(J B1PR?’?P”?b ¤ %?()?@IA(J B1PR?’?Pc? €üàeèT3? Pa-×L'^z02??D”?￡·?+?X?S¨0ííb??wp?ò?4,h ¤vK?ê??e¨t?à1á óó￥b?Tìé?N??L#u a????§-Y‘±27?Z?g%{^ ?? ?NúoQ¨°A?ê?F-na–Dìyà?=÷?1 >?¤y?á?[ót?￥€—owKá/?y4Z1%*lvG{1Ymà?ú?”m?it?i|êN}c÷7-}?′??i?o?×do-1'“V?S???)?TKx??.‰aF???TcúJ?;￥?>:y°±?{è÷kù‰1???XR￡“wZ???”Z?·Z￡?Uuí???¨y6iòjSjJ-A?ê?oMV????CX"??p6u}ìüS??× aoì?°??K??3w?￡k>lTvàk9?±￠#_?3vKE??·?9??S?Q?j?xò+^Yy3|ü?””idaí/?jOw:?^fké3[K?á?‘qk?úD?6èP}W???pa?aa@ìM–?2[*?ho???R?bào1án??A?Y?A|??...

If I'm doing this:

if( strlen($unterschrift) > 0){
    $img = sigJsonToImage( $unterschrift );
};

and try to output:

if ( $imgProceed == "true" ){
    $pdf->imagepng($img);
} else {
    $pdf->Cell(50,4,'',0,1);
}

all I'm getting is:

`Call to undefined method PDF::imagepng() `/ `strpos() expects parameter 1 to be string, resource` 

Can someone explain to me, what I'm doing wrong or what I need to do to include the image in a cell in fpdf? I'm clueless.

Thanks!

Answer 1

The issue is here

$pdf->imagepng($img);
                 ^-------------- This should be an image path (String)

Solution

$file = 'signature.png' ;
imagepng($img, $file);  
                 ^----------- Save Image to File Instead 

Then

if ($imgProceed == "true") {
    $pdf->imagepng($file);
} else {
    $pdf->Cell(50, 4, '', 0, 1);
}