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I have been using Sketchbook Mobile on an android phone a little bit and, being an android (me and the device), I have located the single save file the program allows and make backups of that file on my external sd card so that I can revisit the drawing should I desire.

Does anyone know what file storage format this program uses? (named "sketch" with no extension; supports layers)

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It only allows one save file? :-/ not ideal... I generally find Infinite Painter to be better than SBM - also, the guy behind it has a pressure-sensitive galaxy note version, a vector drawing app (Infinite Design) and an animation app (Animation Studio), as a kind of Android design suite. – user568458 Dec 6 '13 at 17:36
freeware mobile app. Mostly interested in the file format rather than alternative programs. – horatio Dec 6 '13 at 17:42
It may well be a proprietary file format. Can't you export your "Gallery Image"? See… on page 30. – Takkat Dec 6 '13 at 22:04
up vote 3 down vote accepted

I copied the file to my server, viewed the hex data for the first 512 bytes and noted that the first two bytes are ascii II which I recognized from previous experience as the intel byte-order flag for TIFF.

I gave it a TIFF extension and my desktop OS created a preview thumbnail automatically which matched the contents of the sketch.

So: it is a TIFF file with layer support.

I altered the canvas size and it opened just fine within the Sketchbook program (when placed in the proper directory and named appropriately).

I did not test compression methods (LZW RLE JPG etc) nor did I probe the size and memory limitations on the android device.

Note that this means you can easily "back of the envelope" something on the train etc and then bring it into your desktop environment without having to export and lose layer compositing.

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Glad you figured it out. I was wondering about this as well. – ckpepper02 Dec 10 '13 at 17:14
Many years ago I wrote a small program that made a decision process based upon image information for TIFF, jpeg and SCT(!) files. I will tell you how relieved I was when I saw the II tag, because not knowing would have bothered me greatly :) – horatio Dec 10 '13 at 17:21

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