In article <161120032057328513%com>, None <com>

wrote:

I haven't done it myself, but you build your transform matrix as follows:

Translate so the flip axis gets moved to the X axis, apply the identity

matrix, except use -1 for the Y column, then translate back to the

original position. (Since Y is now flipped, this _might_ be in the

opposite direction from what you'd niavely expect.)

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