X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~yarrgweb/git?p=ypp-sc-tools.web-live.git;a=blobdiff_plain;f=pctb%2FREADME.charset;h=25eb5d88feb9e6d8ad603533610219eb34c682b5;hp=bbabb057e6bedd1016f92dd1d2fc63acc41ac24f;hb=276388b200fb1d938558ffea66938034e988da88;hpb=2337ae5465a29659b44037dcbdaf6fa03eb46d84 diff --git a/pctb/README.charset b/pctb/README.charset index bbabb05..25eb5d8 100644 --- a/pctb/README.charset +++ b/pctb/README.charset @@ -1,30 +1,25 @@ -Character set query tool, and semantics of the glyphs ------------------------------------------------------ - -Sometimes the OCR will not be able to recognise some text and you will -have to help it out. It will display the part it is having trouble -with, showing where it has got to, and allow you to edit the character -set database it uses for recognising the text. +Handing OCR failures +-------------------- -*This 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* +Sometimes the OCR will not be able to recognise some text. By +default, when this happens, the program will stop with a fatal error +and refer you to this document. -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). +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. Recognition algorithm --------------------- 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 @@ -34,35 +29,63 @@ So you should not be surprised if the program has matched the 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 @@ -77,16 +100,15 @@ recognised as. *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 `yG' is treated as `y' and the G doesn't get matched. Select the `y' -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 @@ -94,32 +116,70 @@ 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). + +It is also possible to have the OCR system reject particular strings. +If you put a regexp in #local-reject#.txt, any OCR result which +matches this string will instead cause an OCR failure, invoking the +OCR dictionary editor if appropriate. #master-reject#.txt is the +centrally maintained version of this file. + +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. So run + ./ypp-commodities --edit-charset +In future, this option is not usually needed, because it is the +default if there is a local character set dictionary #local-#.txt +for the relevant character height. + +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 dictionary it +uses for recognising the text. + +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. 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. -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 :-). +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).