hassiba and 
rexrainbow can you please edit the "canvas" plugin and post to dropbox and share the link so those who are getting a black screen error (like me) can be assisted once and for all.
I actually believe in this edited plugin of yours
Hi
It has been over 3 years, can not remember a thing
but I found some notes, this is what I have, I hope it helps:
Canvas edittime.js:
AddStringParam("filename", "enter file name", "myfile.png");
AddAction(44, 0, "savetofile", "Canvas", "savetofile", "savetofile", "savetofile");[/code:2pgq000y]
Canvas runtime.js:
[code:2pgq000y]acts.savetofile= function(myfile)
{
var imageData = this.canvas.toDataURL().replace(/data:image\/png;base64,/,'');
cordova.exec(null, null, "Canvas2ImagePlugin","saveImageDataToLibrary",[imageData]);
};[/code:2pgq000y]