Question: I kept on getting: `ArgumentError: Error #2015: Invalid BitmapData.` error whenever I tried to handle image of 5184 × 3456 dimensions, until I wasn't told by my friend that there is a limit in Flash, but he didn't know what was it exactly and I can't find anything on official doc pages.

Does any one know what it's all about? Have a link to Adobe page maybe?

Answer: 
In the docs (http://help.adobe.com/en\_US/FlashPlatform/reference/actionscript/3/flash/display/BitmapData.html) it says:

In AIR 1.5 and Flash Player 10, the maximum size for a BitmapData object is 8,191 pixels in width or height, and the total number of pixels cannot exceed 16,777,215 pixels. (So, if a BitmapData object is 8,191 pixels wide, it can only be 2,048 pixels high.) In Flash Player 9 and earlier and AIR 1.1 and earlier, the limitation is 2,880 pixels in height and 2,880 in width.

so your 5184 × 3456 is too much = 17.915.904 pixels
Also, this page might be helpful:

<http://www.bit-101.com/blog/?p=1426>

Note: the limit in Flash Player 9 is 2048 px. for width, 2048 px. for height.