Size and Format
We use PNG format for signatures because it supports transparency.
In general we set a width of about 205 pixels for convenience and consistency as a sort of "boundary" within which we keep the signature.
Approximately 205 x 65 pixels. 150 DPI or better.
We record them as monochrome and we find that most of our signature images are between 2k - 6k in data size, although we do have some that approach 20k.
We have tested a number of ways to scan in the signatures and found the below methods give good results:
1. Have the users sign an A4 sheet of paper with a marker pen. Scan this using an MFD or scanner and use MS Paint to reduce the size and save as .png.
2. Ask your users to download an app called Digital Signature App from the App Store or Google Play. They can sign on the screen of their phone and send you the result.
Making the Signature Transparent
We use a free program called GIMP available here
- Open Signature.png in GIMP
- Layer | Transparency | Add Alpha Channel is greyed, so the image already has an alpha (transparency) channel
- Layer | Transparency | Color to Alpha. The color to be made transparent is probably white by default.
- Export the modified image to a new PNG file.