If you ever dissect an uncompressed pages file there's a lot of junk in there you really don't need. My guess would be that this is a case of that, Apple including the default fill pattern when it need not be included.
Uncompressed, an empty pages file includes about a megabyte of XML for a 3x3 sheet with tons of absolutely unnecessary default metadata about the sheet as well as each individual cell. Pages really isn't very good at knowing what it actually needs to include.
I spent a few days dissecting the format a few years back at a previous job for a data processing tool. We decided it wasn't worth our time.
As for the size, some things simply don't compress well in PNG.
The image1.png file included by Excel is definitely an image that the author used in the spreadsheet, not a piece of cruft. Since he provides a copy of the xslx file, it's trivial to check:
The file in the OP's article was generated by Numbers, not Excel. The png file in your link is there for a reason, since an image (a logo) was added in an Excel spreadsheet.
Can't be just a placeholder. If it was, it would be a single color for a better compression. Hence the whitenoise - it helps to maintain compression ratio low.
Or more simply, just MD5 them from two machines and see if the hashes (and sizes) match. It is actually quite hard to find hidden text in "random" images. Quite easy to tell if they're identical always however...
If the distribution of bits in an encrypted stream is indistinguishable from normal image dithering, wouldn't encrypted steganography be hard to detect?
It wouldn't survive any lossy image transformations, though.
Randomness is something that cryptographers have spent a lot of time studying.
Introducing non-random data into a random data stream is easy to find unless you're very careful about the amounts of data-to-be-hidden and cover-data.
Pages does it too. Export a document in DOCX format and you get the same PNG file. Export a document in Word 97-2003 format and you get three of these PNG files!
Here's something interesting.
The image only has 47 unique RGB values in it.
47 is such an arbitrary amount though. It doesn't go into power of two cleanly.
From the looks of the OOXML format, the image there is just used as a resource. http://web.mit.edu/~stevenj/www/ECMA-376-new-merged.pdf xl/theme/_rels/theme1.xml.rels refers to image1.png. I'd say it's a default background of some description. Still, it would be cool if there was something in there. Maybe taking a look at the frequency of the bytes would help?
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[ 3.1 ms ] story [ 65.0 ms ] threadhttp://f.cl.ly/items/1X0M2o0V0f3A463c0a2H/Untitled_numbers.p...
Uncompressed, an empty pages file includes about a megabyte of XML for a 3x3 sheet with tons of absolutely unnecessary default metadata about the sheet as well as each individual cell. Pages really isn't very good at knowing what it actually needs to include.
I spent a few days dissecting the format a few years back at a previous job for a data processing tool. We decided it wasn't worth our time.
As for the size, some things simply don't compress well in PNG.
Edit: Sure, downvote me ;)
http://i.imgur.com/j1A5vvC.png
So you are mistaken.
It wouldn't survive any lossy image transformations, though.
Introducing non-random data into a random data stream is easy to find unless you're very careful about the amounts of data-to-be-hidden and cover-data.
http://mcmillan.cx/blog/2014/05/31/bloated-exports-from-page...