Preserve the iTXt chunks. Specify (and, if necessary, correct) the angle direction. #69
Description
The iTXt chunks (say, specifying Title and Author) are lost when deskewing a source PNG file into a target PNG file. The tool should copy them from the source to the target.
Further, the help of the tool (deskew --help) should specify what the sign of the skew angle means when the option -s s is used. Bear in mind that in traditional mathematics on a blackboard, the Y axis points upward, and rotating by a positive angle means rotating counterclockwise, whereas in the logical representation of certain screen coordinate systems, certain image formats, and in ImageMagick, the Y axis points downward (as (0,0) is at the top-left corner), and rotating by a positive angle means rotating clockwise. If necessary, the sign of the reported angle should be reversed. (Subjective view: for easier interoperability, I'd prefer the same convention as in ImageMagick.)