Re-Included the validation_png.php from 2.6 with some changes.
Modified validation_png.php so:
Full path to ttf font is included.
If the specified font file does'nt exist it will automatically revert to bitmap mode.
Characters wont be 'cut off' if size limits are exceeded.
Vertical position variations with ttf fonts occurs.
Randomization function is improved.
Added option to vary maximum character angle variation in admin.
In function account_validation.php Removed 'I' from character list, too easily confused with '1', but added a few other common characters. Removed pointless char replace.
Added instuctions to upload font files.
Personally I would only add the feature to create account and password forgotten, so as not to annoy logged in customers.

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