vang.nguyen

How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Team,

I am trying to figure out the way to convert the unit measurement in our system (millimeter) to OneSpan unit.

Today we use this formula to convert the signature coordinates in my application to OneSpan:

my application value ( in millimeter) x 3.6869 = OneSpan value

for example:

  • signature field in my application
    • top: 259.09592476489024
    • left: 27.07210031347962
    • width: 60.912225705329135
    • height: 20.30407523510971

will be converted to below and submit to OneSpan

[
  {
    "id": "document_id",
    "role": "signer_role",
    "optional": false,
    "fields": [
      {
        "id": "d1e100000",
        "page": 0,
        "type": "SIGNATURE",
        "subtype": "CAPTURE",
        "binding": null,
        "value": null,
        "top": 955.2607650156739,
        "left": 99.81212664576802,
        "height": 74.85909498432599,
        "width": 224.577284952978,
        "validation": null,
        "fontSize": 8
      }
    ]
  }
]

The problem that we are dealing with this formula right now is sometimes when the signature placed too close to the edges it will convert to the coordinates that outside the boundary and throw below error:

 

{
  "messageKey": "error.validation.invalidPageLocation",
  "parameters": {
    "approvalDataName": "",
    "documentName": ""
  },
  "message": "Invalid position. Object placed outside of document page boundary.",
  "code": 400,
  "name": "Validation Error"
}

 

So it will be helpful if someone can help us understand the measurement unit that OneSpan using so we can come up with better conversion.

 

Thanks,

Vang Nguyen


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Vang Nguyen,

 

Thanks for your post!

OneSpan Sign doc engine uses 93.6dpi (inch to px) to convert document pages, that makes:
1mm = 1/25.4 * 93.6 px

This is slightly smaller than 3.6869 that's maybe why the right bottom edge exceeds the page boundary. If you floor this number (1/25.4 * 93.6), it should help avoid the issue.

Let me know how this works for you.

 

Duo

 

Duo Liang OneSpan Evangelism and Partner Integrations Developer


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Thank you so much for your quick response, we will try it and keep you posted.


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Duo Lang,

We have applied the fix to use (1/25.4 * 93.6) = 3.685 (round to 4 decimal) but the issue is still happening, I think it is because of the page is long and we place the signature close to bottom edges, it would introduce more gap on this conversion. floor this (1/25.4 * 93.6) would resolve the issue but we will have big gap on my signature placement tool vs. actual signature appear on OneSpan signing document. I wonder if OneSpan has any API that can tell us the height of the document beforehand? that way we can validate my signature coordinates and adjust it before submit to OneSpan.

Thanks,

Vang Nguyen


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Vang Nguyen,

 

Thanks for your reply! For a 8.5in * 11in A4 page, OSS converts it to 796px * 1030px, using 93.6dpi. 

Below is an example from my test:

I've added a text form at bottom right, and the Adobe Acrobat shows the position is (see the attachment):

Top = 257.5687 mm

Left = 174.5691 mm

Height = 41.2166 mm

Width = 21.6027 mm

After conversion they became:

Top = 949.1406 px

Left = 643.2863 px

Height = 79.6070 px

Width = 151.8872 px

 

In OSS system, the locations are stored as:

height: 80 px

left: 643 px

top: 949 px

width: 152 px

page size is:

width: 796 px

height: 1030 px

There's one pixel gap in bottom and right which is kind of inevitable since numbers are stored as integer in OSS.

 

If you are experiencing a big gap on signature placement tool vs. actual signature appear on OneSpan signing document, could you give me an example and I will look closer into that.

 

Best Regards,

Duo

 

 

Duo Liang OneSpan Evangelism and Partner Integrations Developer


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Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Please help to run below test

my system signature coordinates:

height: 14.877061040024874
width: 44.631183120074624
left: 165.44798354659204
top: 282.16182784886405

document size:
height: 297.0388888888889
width: 210.07916666666668

 

document size in OneSpan

{
  "id": "",
  "left": 0.0,
  "width": 774.0,
  "height": 1093.0,
  "top": 0.0,
  "version": 0,
  "index": 2
}

 

with the pixelDensity=3.685

my conversion would be

top: 282.16182784886405 x 3.685 = 1039.766335623064

height of signature: 14.877061040024874 x 3.685 = 54.82196993249166

top + height = 1094.58830555555566 so it is like 1.58px off the page.

 


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Vang Nguyen,

 

I think your page is slightly longer than 279.4mm (11inch), hence can you share a blank PDF with this page size for me to test?

 

Duo

Duo Liang OneSpan Evangelism and Partner Integrations Developer


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Please use the attached PDF for testing we got the issue on 3rd page


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Hi Vang Nguyen,

 

Thanks for the information! I think the issue is caused because the coordinates are only stored as integer in OSS system. Does floor to get lowest integer work for you since it's at most 1px offset? So you have:

top: 282.16182784886405 x 3.685 = 1039.766335623064 = 1039

height of signature: 14.877061040024874 x 3.685 = 54.82196993249166 = 54

 

Duo

 

Duo Liang OneSpan Evangelism and Partner Integrations Developer


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

Thank you so much, We will try to floor that number before sending it to OSS and I will keep you posted.


Reply to: How to convert signature coordinates from millimeter unit to OneSpan unit?

0 votes

BTW,

We are trying to mimic the OneSpan page size calculation but the result is just one pixel different. I am trying figure out the rounding in OneSpan

This the formula that we use

pixel = Math.round((points * 93.6) / 72);

My result:

Page Sizes:

Page 0 - Width: 796, Height: 1030

Page 1 - Width: 796, Height: 1030

Page 2 - Width: 774, Height: 1094 // This third page is one pixel different to OneSpan result

One Span result

"pages": [
  {
    "id": "",
    "left": 0.0,
    "width": 796.0,
    "height": 1030.0,
    "top": 0.0,
    "index": 0,
    "version": 0
  },
  {
    "id": "",
    "left": 0.0,
    "width": 796.0,
    "height": 1030.0,
    "top": 0.0,
    "index": 1,
    "version": 0
  },
  {
    "id": "",
    "left": 0.0,
    "width": 774.0,
    "height": 1093.0, // The different is on this page
    "top": 0.0,
    "index": 2,
    "version": 0
  }
]

 


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