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cmap [2020/02/23 10:29] christian [Decoding] |
cmap [2020/02/23 13:33] christian [Mappings outside the codespace] |
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| * the mappings are ordered. This is not strictly prescribed, but recommended by the specifications. | * the mappings are ordered. This is not strictly prescribed, but recommended by the specifications. | ||
| - | ==== Handling malformed CMaps ==== | + | ===== Monster from the wild ===== |
| - | Sometimes CMaps define mappings which are not covered by the codespace ranges. This can be seen very often in the wild. These illegal mappings are collected into the ''# | ||
| - | ===== Examples from the wild ===== | ||
| - | single byte mappings in a double byte codespace | + | ==== Mappings outside the codespace |
| - | using /find instead of / | + | <code postscript> |
| + | %... | ||
| + | 1 begincodespacerange | ||
| + | < | ||
| + | endcodespacerange | ||
| + | 27 beginbfchar | ||
| + | <20> < | ||
| + | <2E> < | ||
| + | <43> < | ||
| + | <44> < | ||
| + | <45> < | ||
| + | %... | ||
| + | </code> | ||
| - | preventing copying | + | Here are single byte mappings in a double byte codespace which is not correct according to the documentation. |
| + | This can be seen often. These illegal mappings are collected into the ''# | ||
| + | ==== Wrong PostScript ==== | ||
| + | |||
| + | using /find instead of / | ||
| + | |||
| + | See [[postscript# | ||
| + | ==== Prevent copying ==== | ||
| + | |||
| + | <code postscript> | ||
| + | %... | ||
| + | 1 begincodespacerange | ||
| + | < | ||
| + | endcodespacerange | ||
| + | 100 beginbfchar | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | %... | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | < | ||
| + | %... | ||
| + | </ | ||
| + | |||
| + | Here, all codes map to the same character (Substitute character, Ctrl-Z) to prevent extracting the text. Interesting is also the ordering by the second byte, which forced me to redesign the object structure to avoid exponential processing time. | ||
| + | |||
| + | Seen in [[https:// | ||
| + | ==== Char to string mapping ==== | ||
| + | |||
| + | <code postscript> | ||
| + | %... | ||
| + | /CMapType 2 def | ||
| + | 1 begincodespacerange | ||
| + | < | ||
| + | endcodespacerange | ||
| + | 1 beginbfchar | ||
| + | < | ||
| + | endbfchar | ||
| + | 1 beginbfchar | ||
| + | < | ||
| + | endbfchar | ||
| + | 50 beginbfrange | ||
| + | < | ||
| + | %... | ||
| + | </ | ||
| + | |||
| + | It looks as if two codes (<24> and <50>) are mapped to a string of 2-byte characters. I have not found anything about this in the documenation. Seen in a PDF with the '' | ||