[PDFBOX-5281] Error rendering png from PDF - Error at Type1Parser parseBinary for Type 1 Font

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.23
• Fix Version/s: 2.0.25, 3.0.0 PDFBox
• Component/s: FontBox
• Environment: Component: Type1Parser ; Environment: Java 8
• Assignee: Tilman Hausherr
• Reporter: Fernando
• Created: 20/Sep/21 18:58
• Updated: 17/Dec/21 06:50
• Resolved: 22/Sep/21 16:29

Description

When I try to convert a pdf page using  "pdfRenderer.renderImageWithDPI" to a png image using pdfbox version 2.0.23 I get the following error. The pdf is a customer specific one, I can't share the original file here.

 

Error  [PDType1Font] Can't read the embedded Type1 font
AAAAAB+NimbusMonoPS-Regular_00
java.io.IOException: Found Token[kind=NAME, text=readonly] but expected def
at org.apache.fontbox.type1.Type1Parser.read(Type1Parser.java:867)
at org.apache.fontbox.type1.Type1Parser.parseBinary(Type1Parser.java:610)
at org.apache.fontbox.type1.Type1Parser.parse(Type1Parser.java:64)
at org.apache.fontbox.type1.Type1Font.createWithSegments(Type1Font.java:85)
at org.apache.pdfbox.pdmodel.font.PDType1Font.<init>(PDType1Font.java:263)
at
org.apache.pdfbox.pdmodel.font.PDFontFactory.createFont(PDFontFactory.java:76)
at org.apache.pdfbox.pdmodel.PDResources.getFont(PDResources.java:146)

 

Using the PDFDebugger to have access to the FontFile of the page throwing the error, "Save the Stream as PFB", and using the  t1utils t1disasm to obtain the readable equivalent of the binary private dictionary, which contains:

/Private 10 dict dup begin
/RD {string currentfile exch readstring pop} readonly def   ←
/ND {noaccess def} readonly def
/NP {noaccess put} readonly def
/MinFeature {16 16} readonly def

And following the trace in PDFBox I can see it blowing up at "Type1Parser" in the "parseBinary" method at line 602 they have the check for ""RD".equals(key)", where key is "readonly" and the last check from that list "read(Token.NAME, "def");" has to be def, and because the key is "readonly" it throws the error, even if it makes it pass "RD" it will have the same results when parsing the contents for "ND" and "NP".

I have seen most of the Type 1 Font files have "executeonly" instead of "readonly" in the /Private dict section, even this same file if I convert it first to PS and back to PDF, extracting the font again I can see that the instructions for RD, ND, and NP are rearranged to be "executeonly" using Mac Preview or GS ps2pdf., and the PNG is generated without issue using the PDFRenderer, I don't see a way to do this step programmatically at the moment.

dup /Private 20 dict dup begin
/-| {string currentfile exch readstring pop} executeonly def    ←
/|- {noaccess def} executeonly def
/| {noaccess put} executeonly def

From the Type 1 Font Spec, they don't provide a must follow receipt on what instructions can be appended after RD, ND, or NP, they state: "The RD, NP, and ND functions must be implemented by PostScript language procedures" , If we take a look to the PostScript Language Reference Manual:

readonly: When an object is read-only, its value cannot be modified by PostScript operators (an invalidaccess error will result), but it can still be read by operators or executed by the PostScript interpreter.

executeonly: When an object is execute-only, its value cannot be read or modified explicitly by PostScript operators (an invalidaccess error will result), but it can still be executed by the PostScript interpreter—for example, by invoking it with exec

 

Both "readonly" and "executeonly" allows the instructions to be executed.

Suggestion:

1. Would it be possible to add an optional "readMaybe(Token.NAME, "readonly");"  to the "parseBinary" RD, "ND", and "NP" keywords similar to how it was done at  PDFBOX-2202.