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you can use TransType Pro (http://www.fontlab.com ) or Adobe FDK for OpenType to do the conversion, but it is not trivial. Most likely, the converted fonts will not perform identically as the Type 1 fonts (there will be small changes in behavior depending on the applications and operating system).
What kinds of 'small behavioral changes' might there be? I've been
under the impression that a straight conversion, without adding any
open-type features, would be completely transparent.
A conversion can never be fully transparent for such a complex entity as fonts.
For example, in OpenType, there are two kinds of kerning information (GPOS and kern table). Depending on the conversion method, you may convert the Type 1 kerning into one or both types, but for PostScript-flavored OpenType fonts, kern table-based kerning is not supported. So you will have to use GPOS kerning but there are some applications that don't support it, and with some other applications, only the Western subset of the kerning table will be exposed even if the Type 1 font contained more pairs.
Another example: OpenType fonts contain three different set of linespacing values, one used in most Windows applications, one used in most Mac applications and one used in the typographically sophisticated applications such as Adobe's. There are important technical limitations regarding each of those sets of values. Type 1 fonts only have one set of values and the font driver computes certain aspects of it (i.e. line gap) automatically. When converting, you'd need to make sure that the original Type 1 linespacing values are converted appropriately into each of the sets, but in some cases there may be insolvable conflicts between the values that "should be" there as a result of the conversion and the values that "should be" there due to the technical limitations.
Yet another example: Mac Type 1 fonts typically contain one family name for an arbitrary number of styles, plus a set of style-linking associations. Windows Type 1 fonts typically contain one family name for no more than four styles, and the style-linking associations mimic those styles. OpenType fonts contain both a naming scheme that allows one family name for an arbitrary number of styles (for use in Mac and Adobe applications) and a scheme that allows one family name for no more than four styles (for Windows applications), and also allow style linking. But there are, again, some technical limitations around it, and it is often not possible to automatically map the Type 1 naming schemes into OpenType naming schemes.
These are just three examples, there are more.
In my experience, a fully automated successful conversion from Type 1 to OpenType is quite difficult and requires technical knowledge of the OpenType specification beyond an average user's skills.
Thank you very much for the detailed information. It will be very
useful. And it's also sending me back to rereading the relevant specs!
The issues of different types of kerning, setting font family metrics (i.e. the linespacing values) and the family naming have been covered at:
(the "Recommended Reading" section)
Thanks for your input and it really very useful important information here.