Save signature image to file from HTML
Solutions are as follows:
Download the additional HTML samples from GitHub.
Amongst these there is an HTML sample called demobuttons-save which illustrates how to save a signature to a canvas - in particular please see the function generateImage().
Once the signature is on a canvas it can then be extracted in JPEG or PNG format using toDataURL.
You can then create a Base64 encoded string representing the image which can be submitted to the server and converted to an image file.
To create a file outside IE see CaptureImage.js in the Signature SDK Samples - Jscript folder.
Alternatively in IE you can use RenderBitmap to create a Base64 string representing the image file. This can be submitted to the server where it can be converted to a file.
The Signature SDK samples can be downloaded from GitHub.