Re: [NTG-context] cjk texts in the pdf file which MkIV output sometimes can not be copy rightly

2010/9/20 Li Yanrui (李延瑞) :

2010/9/10 Taco Hoekwater :

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On 09/10/2010 02:32 PM, Li Yanrui (李延瑞) wrote:

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2010/9/10 Li Yanrui (李延瑞):

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Hi all,

For the pdf file which is generated frome the following example, two Chinese characters can not be copied rightly when I use simsun.ttc font and use *Adobe Reader* to view it. The copy text is displayed as the wrong unicode text such as "􁨀".

It looks like the reader is ignoring the ToUnicode entry in the bad case. No idea why, though.

My friend sent a mail to Ken Lunde who works for adobe systems incorporated. He replied:

[quote] I forwarded your email to the Acrobat team for investigation. When I copied the body text from the first file, and all of the text from the second file, the code points are PUA, specifically Unicode Plane 16. The heading text of the first file appears to be encoded correctly. I am guessing that this is a PDF producer issue. I will keep you posted about what the Acrobat team discovers. [/quote]

In the above, the first file is the tex file of the pdf file which is the attachment for my previous mail; the second one is that attachment.

Recently Ken Lunde replied again:

Gu Hua forwarded your email to the Acrobat, which investigated this issue.

The evidence points toward a malformed or poorly-made ToUnicode table. It would be appropriate for Adobe Reader to ignore such a ToUnicode table.

It would be useful to know how the ToUnicode table is made by this PDF producer. I know that when making a static ToUnicode mapping resource, which uses CMap resource syntax, it is very easy to make an invalid one, specifically because CID ranges, when expressed as two-byte values, cannot cross first-byte boundaries. Also, UTF-32 (and UTF-8) cannot be used directly, and such values must be converted to UTF-16. One or both of these issues, if not handles correctly, can result in an invalid ToUnicode table.

In fact the text with fonts such as simsun.ttc can not be copied rightly but the text with fonts such as AdobeSongStd-Light.otf can be copied rightly. It seems like that this problem may be related to the font loading script of mkiv. -- Best regards, Li Yanrui (李延瑞)