Convert Topaz Sigweb sigstring to Base64

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春和景丽 2021-02-08 23:15

I am working on a mobile application(ionic) where there is a field for user\'s signature. Users needs to sign with their finger in canvas.

Now this application has web v

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名媛妹妹 (楼主)

2021-02-09 00:02

I have spent 2 days fiddling with this code, and countless hours (months even) over past 10 years using SigPlus/SigWeb from Topaz.

And when I stumbled upon Scott's answer here, I just had to make it work. Unfortunately, @ScottG made few crucial errors so it didn't work out of the box, and my colleagues that tried it also failed due to lack of documentation. So my answer is 99% built on Scott's code and input, but I am adding:

sample SigString to work with
fixes that needed to be done
requirements
more comments
SigString structure explained
bonus code for HTML5 canvas

Anyway, since the whole story needs to be told, so I am putting the whole example here, not just the (fixed) PHP function.

If you are anxcious to just copy/paste code and move on - skip to actual code. If you want to learn how it works, read it all.

First we need to know that this code (just like Scott's from which it had been built) works only if SigString is neither compressed nor encrypted. If you have previous database of signatures, it's time to convert those to uncompressed/unencrypted ones. This is first step, and reason why others gave up on Scott's code right away. Unfortunately explaining compression/decompression is out of scope of this answer (and I hit character limit, so see my GitHub).

Here is example SigString generated with Topaz tablet, saved by using SetSigCompressionMode(1) ("1" = Lossless compression at a 4 to 1 ratio):

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

This is same SigString converted to SetSigCompressionMode(0) (no compression):

3139370D0A ...  ... 3132300D0A

Bonus: If you really need to save space on disk/in database use this instead of built-in SigWeb/SigPlus compression, down in code there is same example SigString that was uncompressed, and then compressed using PHP's built-in gzdeflate function, you actually get even smaller output this way.

Now, I want to explain the SigString format (base on my sample SigString). Below is output of raw string, right after hex2bin conversion (cropped for readability):

Note we actually have 4 segments here:

line 1 (sample: 197) is amount of coordinates or "points" we have in our signature file, those are number pairs that will start at line 3
line 2 (sample: 4) is number of lines we have, or better said, number of breaking points we keep, and those are single-number entries at very end of file (in this sample: 0/41/93/120)
line 3 onwards we have all those (197) lines with coordinate pairs, logically, this will be as small or as long of a list as your signature actually has. To make it absolutely clear, if line 1 said "5" you would have just 5 pairs, if line 1 said "2999" you'd have 2999 pairs
at end of file we finally have segment with list of those breaking points or end-points that were enumerated by line 2. Again, if line 2 said "3" you would have 3 single-number lines at end of your file, if line 2 said "899" then you would have huge list of 899 single-number lines at end of your file.

As you see from this description, we need to read those first two lines to get started. Later in Scott's code those will be array members, thats arr[0] and arr[1]. Using those two numbers, we can slice the signature into two arrays, one with coordinate pairs, and other with lines, or more correctly - line endings. You can slice it in a number of ways, just keep in mind the format of Sigstring layout.

Using this example we first split the hex2bin result into array, based on provided sample SigString (shortened):

["197","4","451 481","450 480", ... ,"758 223","756 223","756 223"]

And we finish slicing by creating one other array containing "lines" values (again, length of this array is to be cut as long as second element of original array says to):

["0","41","93","120"]

Now, in the code you will see I made a fix, so my actuall "lines[]" array prints this:

["0","41","93","120","197"]

Note that my code-fix added that "197" there at end. That isn't in original signature's end, right? But we still know that from signature's first line, we know it has 197 points, so I just concatenated that to array. Why do that?

Our example signature is simple two letters - "AP" - and has just 4 lines:

coordinates 0 through 41
coordinates 42 through 93
coordinates 94 through 120
and... 121 through 197

That last one isn't clearly described, as it should be obvious, it simply goes from previous line's end (120 + 1) till end of coordinate list. But, well, depending how you do the following steps, your code may or may not need that "197" in lines[] array. For original code to be fixed with minimum changes we need that '197' to be there in array, so that foreach loop can write that last line correctly. We could've fixed it in several obvious ways:

if it is last element in for-each, do different code that uses $done + $arr[0]
we could not need the "lines" as such at all, as you will see in my bonus "HTML5 canvas" code, you don't actually define line start/end as in SVG, you just move your pencil, but sometimes it's moved "on paper" sometimes "in the air"
etc

As explained, you just need to make sure you use all of your coordinates, and to correct original code this was the easiest way (one-liner) without a more through rewrite.

Knowing what we have now, Scott elected for a solution that included another slicing code. He is slicing our coords[] array to separate lines, well, polylines, that he later outputs to SVG. Due to SVG's format, this is actually the prefered way, or at least I see it as such when looking at how Scott did it and what SVG actually looks like inside HTML as end product.

But unfortunately, original code had 2 mistakes (that took me 2 days to solve :) ). One mistake was lacking that last line, and depending on your sample signature it may not be obvious. My first sample had just a dot (signature with "i" letters, so whoever signed it did the dots on the "i" literally at the end, so it wasn't noticable at all, just one dot missing). But this "AP" sample I am providing here actually has whole letter "P" as last line, so missing whole letter made it quite obvious. Anyway, I explained how I fixed that so moving on to second issue.

The other bug was that wrong value was used for slice lengths when slicing to segments/polylines. It actually used the last point to slice it, but array_slice PHP function expects (array, starting point, length) and Scott probably expected it to be (array, starting point, ending point). This too was subtle in some signature samples. What essentially happened was some of the points being re-used, but if you write a line on top of a line, it doesn't matter (specially in perfect digital drawing). But! by re-using coordinates, it sometimes extended one line over the path of two or more lines combined, essentially negating what was ment to happen when "pen" was "in the air", and suddenly all signatures looked as if pen was never removed from paper. Eg. the "dot" on the "i" would be a line connecting "i" and the "dot" (or worse even if you wrote "line" and dotted your "i" after last letter, it would connect the dot with "e", now that's making it pop out)

I fixed that, so now it slices something like this (based on output of my example SigString again):

line = 1 , linevalue = 41 , done = 0 , linelength = 41
line = 2 , linevalue = 93 , done = 41 , linelength = 52
line = 3 , linevalue = 120 , done = 93 , linelength = 27
line = 4 , linevalue = 197 , done = 120 , linelength = 77

I left my sample uncompressed SigString in the code, as well as whole bunch of echos commented out in the code, if you uncomment those you will see this whole process laid out in front of you step by step. And if you comment/uncomment parts of fixed code, you will see same with Scott's version as well, to compare.

I made comments at lines I added, and if it was a change od Scott's line I left his line commented right above my fixed line so you can compare easily. I did not mark all mine vs. his comments, as those can be skipped anyway, my comments just supplement the explanation or explain my changes.

Here is also a link to my GitHub repo, so you can see whole code there as well, together with complete writeup, as I had to shorten stuff here due to Stack Overflow character limit: https://github.com/luxzg/Topaz

If it's not working for you please leave a comment here or raise an issue at GitHub.

Now on to code finally, sorry it took this long. You can just copy/paste whole thing to http://phpfiddle.org/ to see it in action

--- COPY/PASTE EVERYTHING BELOW TO PHPFIDDLE.ORG ---

   //  fix by LuxZg 08.05.2020.

        //Requires $SigString and accepts optional filename.
        //$SigString has to be UNCOMPRESSED and UNENCRYPTED //  by LuxZg 08.05.2020.
        //If filename is supplied the image will be written to that file
        //If no filename is supplied the SVG image will be returned as a string which can be echoed out directly

        function sigstring2svg($SigString, $filename = NULL)
        {
            $raw = hex2bin($SigString); //Convert Hex
            $raw = str_ireplace(array("\r",'\r'),'', $raw); //  fix by LuxZg 08.05.2020. - hex2bin generated code with \r\n both being used
                //  so after exploding it, the \r would be left, sometimes causing more bugs, but otherwise unseen unless encoded to eg. JSON

//          print the binary format
//          echo '

First we echo raw string, after hex2bin conversion:

';
//          echo ''.$raw.''; //  this didn't show \r\n
//          echo ''.json_encode($raw).'';    //  this did show \r\n , and after fix now shows just \n, which is now OK for the next step

            $arr = explode(PHP_EOL, $raw);  //Split into array
            if ($arr[1] > 0) { //Check if signature is empty
                    $coords = array_slice($arr, 2, $arr[0]);    //Separate off coordinate pairs // keep in mind SigString format is: coordinate amount - amount of lines - coordinate pairs - end-points of lines
                                                                                                // also get to know your array_slice format: array name - start of slice - length of slice
                    $lines = array_slice($arr, ($arr[0] + 2), $arr[1]); //Separate off number of coordinates pairs per stroke
                    $lines[] = $arr[0]; // fix by LuxZg - 08.05.2020. - later code needs last coordinate added to array, so last slice/SVG segment isn't ommited by mistake

//                  bunch of echoes below, not needed, except to learn/understand, note that to see \r and/or \n you need to use json_encode, that's why I left both, to debug the error Scott's code had
//                  echo '

Arr[] values:

';
//                  echo '';
//                  print_r(array_values($arr));
//                  print_r(json_encode($arr));
//                  echo '';
//                  echo '

Coords[] values:

';
//                  echo '';
//                  print_r(array_values($coords));
//                  print_r(json_encode($coords));
//                  echo '';
//                  echo '';
//                  echo '

Lines[] values:

';
//                  print_r(array_values($lines));
//                  print_r(json_encode($lines));
//                  echo '


';

                    if ($arr[1] == 1) {
                            $lines[] = ($arr[0] + 2);   //If there is only 1 line the end has to be marked
                        }
                    $done = 0;
//                  we always start at zero, it's first member of array, first coordinate we use

                    foreach ($lines as $line => $linevalue) {
                            if ($linevalue > $done) {
                                    $linelength = $linevalue-$done; //  fix by LuxZg 08.05.2020. - we need to know where slice ends, so we use the "done" of previous line as our new start
                                                                    //  and we know where we need to end, so length is simple math
//                                  $strokes[$line] = array_slice($coords, $done, $linevalue);  //Split coordinate pairs into separate strokes  //  end of line is wrong
                                                                                                //  it was including too many lines/coordinates in each iteration, again and again, so I fixed it, left this for comparison
                                    $strokes[$line] = array_slice($coords, $done, $linelength); //Split coordinate pairs into separate strokes  //  fix by LuxZg 08.05.2020. - end of slice is now length of line, as should be
                                }

//                          just an echo to see what's actually happening and also why we needed to add that one last point in our lines[] array earlier
//                          echo "
line = ".$line." , linevalue = ".$linevalue." , done = ".$done." , linelength = ".$linelength."
";

                            $done = $linevalue; //  we set new value to $done as next line will start from there
                        }

//              I did not touch anything else in this PHP function, from this point below ! SVG drawing code is great!

                    //Split X and Y to calculate the maximum and minimum coordinates on both axis
                    $xmax = 0;
                    $xmin = 999999;
                    $ymax = 0;
                    $ymin = 999999;
                    foreach ($strokes as $stroke => $xycoords) {
                            foreach ($xycoords as $xycoord) {
                                    $xyc = explode(' ', $xycoord);
                                    $xy[$stroke]['x'][] = $xyc[0];
                                    if ($xyc[0] > $xmax) $xmax = $xyc[0];
                                    if ($xyc[0] < $xmin) $xmin = $xyc[0];
                                    $xy[$stroke]['y'][] = $xyc[1];
                                    if ($xyc[1] > $ymax) $ymax = $xyc[1];
                                    if ($xyc[1] < $ymin) $ymin = $xyc[1];
                            }
                    }
                    //Add in 10 pixel border to allow for stroke
                    $xmax += 10;
                    $xmin -= 10;
                    $ymax += 10;
                    $ymin -= 10;
                    //Calculate the canvas size and offset out anything below the minimum value to trim whitespace from top and left
                    $xmax -= $xmin;
                    $ymax -= $ymin;

                    //Iterate through each stroke and each coordinate pair to make the points on the stroke to build each polyline as a string array
                    foreach ($xy as $lines => $axis) {
                            $polylines[$lines] = '';
                    }

                    //Build SVG image string
                    $image = '
                        ';

                    //If file name is supplied write to file
                    if ($filename) {
                            try {
                                    $file = fopen($filename, 'w');
                                    fwrite($file, $image);
                                    fclose($file);
                                    return $filename;
                            } catch (Exception $e) {
                                    return false;
                            }
                    } else {
                            //If file name is not supplied return the SVG image as a string
                            return $image;
                    }
                } else {
                        return "Signature is empty";
                }
        }

//              OK to complete the example I actually use the function

        //  this is my simple example "AP" signature, all decompressed and ready to be put through function
        $sigdec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

        //  Bonus:
        //      if you will need to keep SigString size down, rather use PHP's gzdeflate or anything similar
        //      just don't forget if you later pull the compressed sig data from eg. database, to decompress it before sending it to SVG function
        //  $sigdecgz = gzdeflate($sigdec,9);

//      you can use these echos to see sample SigString
//      echo 'Printing decompressed SigString ; SetSigCompressionMode(0) :

';
//      echo $sigdec;

//      print the output of sigstring2svg, so my sample "AP" SigString, shown in SVG format, using slightly modified Scott's code
        echo '

Printing output of sigstring2svg() function, SigString as SVG (of decompressed & unencrypted signature !):

';
        echo sigstring2svg($sigdec);
        echo '

';

?>

OK, done with PHP ... but there is one more bonus for you folks!
I re-used same PHP code to actually draw the signature in HTML5 canvas, similar as the original SigWeb component does, but without using Topaz APIs/components.
I've re-used the PHP code to do the initial hex2bin and slicing
It is somewhat shorter this way, though not as polished as Scott's SVG.
Tested, works all nice even on combination of Ubuntu / Apache / PHP web server, with Android phone as client, so no Windows involved.





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