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Signature Image with Transparent Background

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Joe Winograd, EE Fellow 2017, MVE 2016, MVE 2015
50+ years in computer industry. Everything from development to sales. CIO. Document imaging. EE MVE 2015, EE MVE 2016, EE FELLOW 2017.
This article is in response to a question here at Experts Exchange. The Original Poster has a scanned signature and wants to make the background transparent so that the signature may be placed on documents without obliterating the surrounding text. Here's an example of the problem, showing how the surrounding document is overlaid when the non-transparent signature is placed on a PDF (in this case, via the Custom Stamp feature in Adobe Acrobat):

Signing PDF in Acrobat with non-transparent stamp
The solution described in this article requires a product called IrfanView, excellent (and free!) imaging software:

At the URL above, click the Download link on the left to download IrfanView and click the PlugIns link on the left to download the PlugIns, which are needed to give you PDF capability. Installing the PlugIns is optional – required only if you want PDF support (and the other features that come with the PlugIns). Install IrfanView first, then install the PlugIns. Although I recommend adding the PlugIns to get PDF support, that's for general, future usage. For this situation, you don't need them, unless your scanned signature is in a PDF file, in which case you do need them.

Here are the steps for making your signature background transparent after installing IrfanView:

(1) Run IrfanView and open the file that has your scanned signature.

(2) I recommend cropping the signature by dragging the mouse from the upper left to the lower right and selecting the Edit menu, then Crop selection. At that point, you'll have something like this:
John Doe sig not transparent(3) Now save the image as a PNG file, which supports transparency. Click the File menu, then Save as. At the bottom of the Save Picture As dialog, tick the Show options dialog box:

Show options dialog
(4) In the Save as type drop-down, select PNG:

Save as type PNG
(5) You will see a separate window with the PNG/PNM/ICO save options, like this:

PNG save options
(6) I have experimented with various settings in the PNG section of the save options dialog, and I recommend the settings shown in the screenshot above. In particular, Compression level 1, which makes the file larger (but still a reasonable size) and the quality higher, is a good idea for a signature (Compression level 0, i.e. no compression, results in a very large file). Also, I've had success using the transparent signature in more products when Save Transparency as Alpha channel is ticked.

(7) Click Save in the main Save Picture As window. Now the critical step occurs – it will ask you to click in the image to set the transparent color:

Click to set transparent color
So click the mouse on the white background (this assumes, of course, that your scanned signature is dark ink on white paper). After you click the white area, it will be transparent!

(8) Exit IrfanView. The PNG file saved in the step above now has your signature with transparent background.

To show how this works, here is a screenshot of the transparent signature placed on a document, using the same PDF file and the same Custom Stamp feature in Adobe Acrobat that were used with the non-transparent signature at the beginning of this article:

Signing PDF in Acrobat with transparent stamp
If you are wondering how to create a Custom Stamp with your signature in Adobe Acrobat, this EE article explains it:
Create Signature Stamp in Adobe Acrobat

Happy document signing – without having to print it, sign it in ink, and then scan it back in.

If you find this article to be helpful, please click the thumbs-up icon below. This lets me know what is valuable for EE members and provides direction for future articles. Thanks very much! Regards, Joe
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Expert Comment

by:Dan Craciun
Excellent article Joe.

Quick questions: what did you use to sign (looks like a brush) on what paper (matte, glossy, regular) and what scanner did you use? Cause the scan result looks fabulous.
LVL 38

Expert Comment

I think you'll find that "John Doe"'s signature was a font, and was for example purposes.
LVL 58
Hi Dan,

Thanks for the compliment – I appreciate it!

I did not scan the sample "signature" in the article. I was not keen on having my actual handwriting exposed to the Internet, whether on my own name or John Doe's name. So for the purposes of the article, I created the "signature" using a script font in Word (Script MT Bold) and capturing it to a JPG file. The gist of the article is how to make the background transparent when a scanned signature already exists, not how to create a fabulous looking signature in the first place – but the latter would make for an interesting article!

I do have signature stamps (both my full name and my initials) that I created years ago – so long ago that I can't say what scanner I used, but it was definitely one of my relatively inexpensive desktop scanners. I'm sure that I used a standard, black ink ballpoint pen on a plain piece of white laser printer paper. The scanning parameters were 600 DPI, black&white (i.e., monochrome/1-bit). I've used these (transparent background) stamps to sign and initial many documents for many years.

I just tested everything mentioned above (black ink ballpoint pen, white laser paper, 600DPI, B&W) with three scanners – Brother MFC-9840CDW (multi-function device), Fujitsu ScanSnap S1500, and Kodak ScanMate i920. The resulting images of the signature look fine. Regards, Joe
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LVL 58
My message just crossed with lherrou's (had a browser tab open). He is spot-on! Regards, Joe
LVL 30

Expert Comment

by:Marc Z
What a great, fast fix!  So simple,  but so hard to figure out without some good guidance.
Thanks Joe.
LVL 58
Thanks for the kind words – much appreciated! Regards, Joe

Expert Comment

Its a good article, but I would like to add one more thing which would completely secure your signature by adding Adobe Flattening tool.

Flattening makes your signature a permanent part of the document, therefore no one would be able to just copy your stamp.  Once you flatten a document it cannot be undone –

To install the flatten tool, use the following steps

1.      Go to http://www.pdfscripting.com/public/Free_Acrobat_Automation_Tools.cfm

2.      Download the flatten tool (just open the folder)

3.      Navigate to C:\Program Files (x86)\Adobe\Acrobat 8.0\Acrobat\JavaScripts

4.      Copy the flatten tool (PDFScript_FlattenPages.js) and paste it into the JavaScript folder

5.      Adobe will need to be restarted for the tool to be available

6.      In versions before Acrobat X, the flatten tool will be on the menu bar once Adobe is restarted.  In Adobe X, the tool can be found in tools, ad-ons once Adobe is restarted

Hope this will help.


Navigate to C:\Program Files (x86)\Adobe\Acrobat 8.0\Acrobat\JavaScripts (Acrobat 8.0 is a version of adobe installed on your computer)
LVL 58
Hi thunder88,
Thanks for the compliment and the comment — both appreciated! I do flatten documents before sending them out, although simply by printing them to a PDF print driver rather than using a flattening tool. But I think your statement that flattening "would completely secure your signature" is too strong. While your statement that "no one would be able to just copy your stamp" is true (since it's no longer a stamp when flattened), you would still be subject to someone creating a stamp from your signature, even though it is flattened on the document. With an image editing tool, such as IrfanView, one could remove the surrounding lines and text to isolate the signature in a bitmap and then create a stamp of it. In fact, creating a stamp isn't even necessary — a copy/paste of the signature image is all that's needed. To be clear, I'm not saying that flattening is a bad idea, but rather that it doesn't afford a lot of protection. If your signature is out there — as an image, flattened or not; or even as ink-on-paper — it's subject to misuse. Regards, Joe
LVL 35

Expert Comment

by:Dan Craciun
If you need secure, use a proper digital signature that uses a certificate.

You can get a free one from Comodo, and use your scanned signature as the display image.

Just click on Place signature, draw a rectangle and follow the wizard.

Expert Comment

by:Mike Caldwell
Joe, just followed your instructions, but when I save I do get the Options page and I fill it in as you direct, but I do not get the prompt to click into the area to be made transparent; I get nothing except saving the file again.  I am using Windows 8.1 Pro, and the program was downloaded and installed just now, so is the current version.

Expert Comment

by:Mike Caldwell
Oops, my bad.  I also had "Use main windows color as transparency" checked, so I was not offered to click into the transparency area.  Once I took that off, worked like a charm.  Many thanks.
LVL 58
You're welcome. I'm glad to hear it's working for you. And thanks to you for the update. Regards, Joe

Expert Comment

Great article Joe! As usual, your explanation and instructions are straightforward and easy to follow.

It's probably a simpleton approach but to avoid the: "print > fill in & sign by hand > scan" approach you mentioned and because forms & other documents needing info & signatures can be of multiple types (eg pdf, Word, online, etc), I have always done the following:

        1) capture a screenshot of the form/doc using the Snipping Tool
        2) paste the image directly into PowerPoint (ie without saving it first)
        3) enter all required info as text boxes (which are easy to modify or re-position)
        4) Insert > Picture > signature
        5) Ctrl+A > Right-click > Group (all objects)
then either:
        6a) Right-click > Save as Picture…
        6b) Snip the completed form and save the resulting screenshot.

Please tell me if I'm mistaken but I've always assumed that doing either #6 option results in an image file which can then be submitted wherever in a form that prevents someone from lifting/altering one of the original single objects (eg the signature).
LVL 58
Thank you, Steve. I appreciate the compliment — and the upvote!

> prevents someone from lifting/altering one of the original single objects (eg the signature)

Yes, it means that the signature is not a live object (it has been burned into the image), but that affords you relatively little protection. Someone can easily lift the signature and/or alter the document with imaging software. This was discussed to some extent in a comment above. Regards, Joe

Expert Comment

Joe, two questions:

1) What site do you use to download software like IrfanView? The link you provided led to a page with about a dozen download links. The first of those (Download.com) resulted in a pop-up notice saying "iview440_setup.exe is malicious, and Chrome has blocked it". I found one of the sites which did not trigger that notice but still wanted me to accept a bunch of extra stuff. I unchecked all those boxes but it makes me wonder what is downloaded and installed without my knowledge. Is there a site where you can count on getting only what you are after and nothing more?

2) After installing and using the IrfanView app, I closed it. But then when I went back to open it again, it was nowhere to be found in my Start > All Programs list of apps and folders. I was only able to find it by Start > Search but that led to the .exe file and I had to go through the install process all over again. Is there something I could be doing wrong or is that just what's required each time you want to use the software?
LVL 58
> What site do you use to download software like IrfanView?

Yes, the download page provides many links, but I recommend the TUCOWS link to download IrfanView:

This will download a single install file called <iviewNNN.exe> or <iviewNNN_setup.exe> with no adware and no junk!

And the TUCOWS link for the PlugIns, which are required for PDF support:

This will download a single install file called <irfanview_plugins_NNN_setup.exe> with no adware and no junk!

In both cases, NNN is the version number (currently 440, meaning Version 4.40).

Install IrfanView first, then install the PlugIns.

There's also a new 64-bit version (started with the 4.40 release), available here:

The download links for the 64-bit core product and the 64-bit plugins are at the bottom of the page. I have both the 32-bit and 64-bit versions installed on the same W7/64-bit system (in different folders) — no problem.

> Is there something I could be doing wrong or is that just what's required each time you want to use the software?

Perhaps you're not telling it to create shortcuts. Here's what I select in the installer:

IrfanView install shortcuts
That gives me an IrfanView program group with shortcuts, as well as a shortcut on the desktop. I keep an ultra-clean desktop, so I move the shortcut into a folder of shortcuts where I have my most frequently used programs. Regards, Joe

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