default, when this happens, the program will stop with a fatal error
and refer you to this document.
-It is possible to fix this by editing the character set database used
+It is possible to fix this by editing the character set dictionary used
by the OCR algorithm. But, it is important to get these inputs right
or your client may misrecognise text in future. You *must* read the
documentation here first.
---------------------
We recognise the text in the commodity screen by doing exact matching
-of `glyph' bitmaps, against the bitmap in each cell in the commodity
+of `glyph' images, against the image in each cell in the commodity
table. We match from left to right.
We do not insist that each glyph is followed by whitespace, and nor do
-we insist that glyphs do not contain whitespace. Our glyph database
+we insist that glyphs do not contain whitespace. Our glyph dictionary
can contain entries which are strict prefixes of other entries - that
is, a glyph for (say) `v' which is the leftmost part of another glyph
for (say) `w'. We resolve these ambiguities by taking the longest
left-hand half of some letter and thinks it is a different letter. If
the part that it did recognise does look like the letter in question,
that isn't wrong. All you need to do is insert the whole of the
-actual letter in the database - move the LH cursor to the start of the
+actual letter in the dictionary - move the LH cursor to the start of the
letter, and the RH cursor to its end, and hit `return' and enter the
correct character. The longest match rule will mean it will prefer
the entry you have just made.
-Upper vs lower case - important note regarding `l' and `I'
-----------------------------------------------------------
+Matching context - Upper/Lower/Digit/Word dictionaries
+------------------------------------------------------
-We maintain separate databases for upper and lower case. At the
-beginning of each cell in the table, we expect uppercase; in the
-middle of a word we expect lowercase; and, unfortunately, after an
-inter-word gap, we are not sure.
+We maintain separate dictionaries for the following types of glyph
-This is troublesome because `l' and `I' look identical on the screen.
-So any time we see a word starting with `l' or `I', the program has to
-ask about it.
+ Upper:
+ Upper case letters and ligatures starting with an
+ uppercase letter. Punctuation excluding `>'.
+ Lower:
+ Lower case letters and ligatures starting with a
+ lowercase letter.
+ Digit:
+ Digits and the greater than sign `>' (which can also
+ appear in the quantity field in the commodity display)
+ Word:
+ Words (or initial parts of words) which start with `l'
+ or `I'.
-*Do not* make an entry in the character set database mapping `vertical
-stick' to `l' or `I'. Instead, select enough of the whole word in
-question that no word would start with the other letter, and enter the
-whole word or part of it as a new glyph.
+When you add an entry, you should add it to the appropriate dictionary
+for its matching context. You can do this by selecting the
+appropriate radiobutton or by pressing one of letters U D L W (the
+initial letters of the contexts) after moving the cursor to the
+appropriate spot but before hitting `Return' to enter the text for the
+new entry.
-For example, in the supplied database there is already a glyph for
-`Iron'; this is OK because there are no words which start `lron'.
-Do not make an entry for a string more than 7 characters long;
-currently we cannot cope (and you'll have to remove it manually from
-the charset-15.txt file).
+Note regarding `l' and `I'
+--------------------------
+
+At the beginning of each cell in the table, we expect uppercase; in
+the middle of a word we expect lowercase; and, unfortunately, after an
+inter-word gap, we are not sure.
+
+This is troublesome because `l' and `I' look identical on the screen.
+So any time we see an unfamiliar word starting with `l' or `I', the
+program has to ask about it.
+
+After an interword gap, we first search for a Word entry in the
+dictionary. If there is a match we use it. Otherwise we search both
+the uppercase and lowercase dictionaries; if one matches and the other
+doesn't, or one matches a wider character than the other, we use it.
+If that fails to resolve the ambiguity we must ask.
+
+Don't try to make an entry in the character set dictionary mapping
+`vertical stick' to `l' or `I'. Instead, select the whole word (or
+enough of it that no different word would start with the other
+letter), and enter the whole thing as a new glyph in the Word
+dictionary.
+
+For example, in the supplied dictionary there is already a glyph for
+`Iron'; this is OK because there are no words which start `lron'.
Short inter-word gaps
*You should check the alleged context before entering a character*.
If it is wrong, you should fix it, rather that just making an entry
-for the uppercase letter in the lowercase database.
+in the wrong dictionary.
-Instead, make a new glyph for the last letter of the previous word
-plus the (unusually narrow) inter-word space, and end that entry with
-\x20 (yes, type \ x 20).
+When this happens, instead, make a new glyph for the last letter of
+the previous word plus the (unusually narrow) inter-word space, and
+end that entry with a literal space ` '.
For example, you might find that `y<space>G' is treated as
`y<??lowercase>' and the G doesn't get matched. Select the `y<space>'
-region of the bitmap and type `y\x20' into the string box.
-Sorry for this rather poor UI!
+region of the bitmap and type `y ' into the string box.
Overlapping characters - ligatures
Some of the characters in the font used overlap with the next
character. When this happens, select both the characters and enter
-them together as one glyph with a multi-character definition.
+them together as one glyph with a multi-character definition, as a new
+entry in the Lower or Upper dictionary.
For example `yw' is rendered with the top right corner of the `y' and
the top left corner of the `w' overlapping. This is dealt with by
matching the whole merged thing - select the region of the screen
containing `yw' and define it as `yw'.
+Such a combined entry - a ligature - is only needed if the letters
+cannot be separated at all. It's not needed if they merely abut.
+
Fixing mistakes
---------------
-The OCR query UI allows you to delete things from the glyph database.
-However since you are not guaranteed to actually get an OCR query at
-all if the database contains errors, you shouldn't rely on this.
+The OCR query UI allows you to delete things from the local glyph
+dictionary. However you are not guaranteed to actually get an OCR
+query at all (and since it is not possible to override the presence of
+an entry in the master database with the absence of one in the local
+database). So this is not a reliable feature for being able to fix
+errors.
If you think you have made mistakes answering OCR queries (for
-example, the recognised data is wrong), you should download a fresh
-copy of charset-15.txt from
- http://www.chiark.greenend.org.uk/~ijackson/ypp-sc-tools/master/pctb/charset-15.txt
+example, the recognised data is wrong), you should delete the file
+#local-char*#.txt, which contains your local updates. It will then
+only use the centrally provided (and vetted) master file (which is
+automatically updated when you run the PCTB client, by default).
+
+Alternatively you can edit #local-char15#.txt with a text editor. The
+format is not documented at the moment.
Enabling interactive character set update
-----------------------------------------
Now that you have read this document, you should rerun your OCR job
-with the --edit-charset option. You probably want to supply --same as
-well, to avoid having to wait for it to page through and recapture all
-the screenshots. So, this time,
- ./ypp-commodities --edit-charset --same
-and in future, just always run it with the --edit-charset option.
+with the --edit-charset option. So
+ ./ypp-commodities --edit-charset
+In future, always run it with the --edit-charset option.
With --edit-charset, when the OCR finds characters it does not
understand, it will put up an OCR resolution query window. This will
display the part of the text it is having trouble with, showing where
-it has got to, and allow you to edit the character set database it
+it has got to, and allow you to edit the character set dictionary it
uses for recognising the text.
-*This is subtle* and it is important to understand the way the
+The process is subtle and it is important to understand the way the
machinery works, and the possible mistakes you can make, before
-answering the program. *Please read this documentation*, which
+answering the program. So *Please read this documentation*, which
explains the meaning of the entries you make.
+The character set updates you make will by default be submitted to my
+server so that they can be checked by me and shared with other users.
+See README.privacy.
+
If you need help please ask me (ijackson@chiark.greenend.org.uk, or
Aristarchus on Midnight in game if I'm on line, or ask any pirate of
the crew Special Circumstances if they happen to know where I am
and/or can get in touch).
-
-
-Send me your updates
---------------------
-
-The character set is in the file `charset-15.txt'. When you enter new
-characters, they are added there. If you do this, please email me
-your charset file (ijackson@chiark.greenend.org.uk) so that I can
-include your contributions in future versions. This will also let me
-check that they seem right :-).
-
-In future I may have the program phone home automatically so that I
-can double-check your answers and distribute them in the next version.
~yarrgweb / ypp-sc-tools.web-live.git / blobdiff