7/28/2023 0 Comments Adobe pdf search wrong characters![]() What type of file do I need and how will it be used?.Here are a few questions to ask yourself before you get started: Given current state of affairs, PDF-creators are NOT advised to mix single and double byte codes in font encoding ( CMAP).When deciding which OCR software to use you should first think of what the outcome of your project should be. Miraculously, 0x0020 code and 32 CID do not interfere. This file appears to open perfectly in all viewers, mentioned in original question and comments below. codespacerange in ToUnicode Cmap deleted.I returned to the original file and changed this: Then I thought, that maybe variable character code width was the issue. Well, it did help, but unfortunately, some of viewers still rejected to comply to specification. (+ later I tried to remove 32 string from CMAP - not reflected in a file, linked in comment).ToUnicode cmap was adjusted accordingly.value in Widths array of CID=4 to 'vav' width.bytes 08 and 09 in CIDToGIDMap to GID=159.This assumption was based on a case, several years ago, when (older version of) Acrobat didn't show character with 0x20 code, when it's at the end of a string - assuming it to be space, when in fact, according to encoding vector (of a simple font), it was another character. In my first attempt, I suggested it's 32 code (and CID) that's used for non-space character (see comment above). Now we have enough information to speculate, what confuses viewer applications To make a long story short, if we look up character codes in CMap and get CIDs, then look up CIDs in CIDToGIDMap and get GIDs, then look up GIDs in embedded David-Bold font and get Unicode values, here's the table Code CID GID Unicode Name Of course there are no 'groups', they are here because I made them, based on CMap that contains 2 ranges: (The end of a short and simplified introduction) From my experience, it's most common scenario, and as it appears, that's the case, against which common software is tested.īut, it's not the case with file in question. In what I call a simple case (and, I think, sensible decision), CMap is predefined Identity-H name, CIDToGIDMap is a predefined Identity name, and, therefore, character codes extracted from a string (argument to text showing operator) are always 2-byte numbers that, effectively, directly select glyphs from embedded TrueType program. ![]() It's called ToUnicode Cmap (as it follows similar syntax), but it should not to be confused with CMap object, mentioned above. Those GIDs are, at last, used to select glyphs from embedded font program (which, for CIDFontType2 font, is a TrueType font program (do not confuse with Font object of TrueType Subtype)).įont object can have ToUnicode resource, that maps CIDs to Unicode values for indexing, searching and extraction. For CIDFont of CIDFontType2 type, its dictionary contains CIDToGIDMap entry, that, obviously, maps CID to glyph identifiers. Now, character selector ( CID) is not, in general, directly used to select glyphs from font program. Type0 font always has one descendant which is a font-like object called CIDFont, and, similar to encoding for simple fonts, a CMap object, that maps character codes to character selectors, which, in PDF, are always CIDs - integers up to 65536. ![]() Composite fonts (Type0), used to show text in which character codes can have variable length (up to 4 bytes), and which, therefore, isn't restricted to 256 code-points.The file in question doesn't contain simple fonts, and we won't discuss them any further - but, note, over-simplistic description doesn't even start to reflect any of real-life complexity. The mapping from codes to glyphs is called the font’s encoding, it can be either built-in into font program or defined by Font object (by predefined name or explicitly) or, under special circumstances, constructed according to defined rules by viewer application. Simple fonts (Type1, Type3 or TrueType), in which glyphs are selected by single-byte character codes obtained from a string that is shown by the text-showing operators.Fonts in layman terms - as we see them as *.ttf or *.pfb files - are called font programs, either embedded or external, and are referred to by one of sub-dictionaries of Font objects. Fonts in PDF are PDF objects - Font dictionaries, containing numerous parameters and sub-dictionaries, necessary to select glyphs, show them and translate character codes to logical (Unicode) representation for content extraction. ![]()
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