These two static members are now used to implement respective `matches_`
methods but will also be useful to provide a global implementation of
the specified concept of whitespace.
TJ acts on a list of either strings or numbers.
The strings are drawn, and the numbers are treated as offsets.
Previously, we'd only apply the last-seen number as offset when
we saw a string. That had the effect of us ignoring all but the
last number in front of a string, and ignoring numbers at the
end of the list.
Now, we apply all numbers as offsets.
Our rendering of Tests/LibPDF/text.pdf now matches other PDF viewers.
Per 5177.Type2.pdf 3.1 "Type 2 Charstring Organization",
a glyph's charstring looks like:
w? {hs* vs* cm* hm* mt subpath}? {mt subpath}* endchar
The `w?` is the width of the glyph, but it's optional. So all
possible commands after it (hstem* vstem* cntrmask hintmask
moveto endchar) check if there's an extra number at the start
and interpret it as a width, for the very first command we read.
This was done by having an `is_first_command` local bool that
got set to false after the first command. That didn't work with
subrs: If the first command was a call to a subr that just pushed
a bunch of numbers, then the second command after it is the actual
first command.
Instead, move that bool into the state. Set it to false the
first time we try to read a width, since that means we just read
a command that could've been prefixed by a width.
Images can have multiple filters, each one of them is processed
sequentially. Only the last one will be relevant for the image format
(DCT or JPXDecode), so use the last filter instead of the first one to
detect that property.
For valid PDFs, this makes no difference.
For invalid PDFs, we now assert during the cast in resolve_to() instead
of returning a PDFError. However, most PDFs are valid, and even for
invalid PDFs, we'd previously keep the old color space around when
getting the PDF error and then usually assert later when the old
color space got passed a color with an unexpected number of components
(since the components were for the new color space).
Doesn't affect any of the > 2000 PDFs I use for testing locally,
is less code, and should make for less surprising asserts when it
does happen.
Namely, for CalGrayColorSpace, CalRGBColorSpace, LabColorSpace.
Fixes a crash rendering any page of Adobe's 5014.CIDFont_Spec.pdf
(which uses CalRGBColorSpace with an indirect dict: The dict is
object `92 0`, and many color spaces are inline objects referring
to it).
I didn't find example code for this and the AI assistant did very
poorly on this as well. So I had to write it all by myself!
It can be much more efficient I think, but I think the overall
shape is maybe roughly fine.
* SampledFunction now keeps the StreamObject it gets data from alive
(doesn't matter too much in practice, but does matter in the test,
where nothing else keeps the stream alive).
* If a sample is an integer, we would previously sample that value
twice and then divide by zero when interpolating. Make sure to
sample 1 unit apart.
* Compare array size to 3 and 4, not 4 and 5
* Fix literal typo in error message
Fixes crash processing 0000906.pdf from 0000.zip from the pdf/a dataset.
We did convert from the input space to linear space and then
to linear sRGB, but we forgot to re-apply gamma.
This uses the x^2.2 curve instead of the real sRGB curve for now.
CalRGBColorSpace::color() converts into a flat xyz space,
which already takes input whitepoint into account.
It shouldn't be taken into account again when converting from
the flat color space to D65.
https://adobe-type-tools.github.io/font-tech-notes/pdfs/T1_SPEC.pdf,
8.4 First Four Subrs Entries:
"""If Flex or hint replacement is used in a Type 1 font program, the
first four entries in the Subrs array in the Private dictionary must be
assigned charstrings that correspond to the following code sequences. If
neither Flex nor hint replacement is used in the font program, then this
requirement is removed, and the first Subrs entry may be a normal
charstring subroutine sequence. The first four Subrs entries contain:
Subrs entry number 0:
3 0 callothersubr pop pop setcurrentpoint return
"""
othersubr handler 0 gets three arguments:
* The flex height (the distance after which the bezier splines
are replaced with just straight lines)
* The current position after the flex
It pushes that position on the postscript stack, where predefined subr
handler number 0 then pops it from. It then passes it to
setcurrentpoint.
In theory, we now correctly do that setcurrentpoint call, which we
previously weren't.
In practice, that setcurrentpoint call always receives the last point of
the flex -- and our path api apparently gets confused when move_to() is
called on it when the current point is already at that same location.
So tweak the SetCurrentPoint handler to not set the current point on
the path if it's already the path's current point, with a FIXME to
figure out what exactly is happening in Gfx::Path.
No big behavior change if flex is used, but this is more correct if it
isn't.
(This only works because our `return` handler is empty, else we would
have to make the callothersubr handler start a call frame.)
https://adobe-type-tools.github.io/font-tech-notes/pdfs/T1_SPEC.pdf,
8.4 First Four Subrs Entries:
"""If Flex or hint replacement is used in a Type 1 font program, the
first four entries in the Subrs array in the Private dictionary must be
assigned charstrings that correspond to the following code sequences. If
neither Flex nor hint replacement is used in the font program, then this
requirement is removed, and the first Subrs entry may be a normal
charstring subroutine sequence. The first four Subrs entries contain:
[...]
Subrs entry number 1:
0 1 callothersubr return
Subrs entry number 2:
0 2 callothersubr return
"""
So subr entry numbers 1 and 2 just call othersubr 1 and and 2, which
means we can just move the handling code over.
No behavior change if flex is used, but more correct if it isn't.
(This only works because our `return` handler is empty, else we would
have to make the callothersubr handler start a call frame.)
Previously we assumed a default precision of 6, which made the printed
values quite odd in some cases.
This commit changes that default to print them with just enough
precision to produce the exact same float when roundtripped.
This commit adds some new tests that assert exact format outputs, which
have to be modified if we decide to change the default behaviour.
This is a subset of #21484: Type 2 CFFs never use the special subrs,
so stop doing them for type 2 at least for now.
Fixes an assert in 0000064.pdf in 0000.zip in the pdfa dataset
(a stack underflow because a subr is supposed to push a bunch of
stuff, but instead it ran one of the built-in routines instead of
the subr from the font file).
As discussed in #21484, this isn't right for type 1 CFFs either,
but just removing the code there regresses Tests/LibPDF/type1.pdf.
A slightly more involved thing is needed there; I added a FIXME
for that here.
Previously, an xref stream with a field with larger than 8 would
result in an undefined shift occurring. We now ensure that each field
width is a number and is less than or equal to 8.
Nothing in PDF 1.7 spec 8.2.1 Destinations mentions the page being
`null`, but it happens in 0000372.pdf (for the root outline element)
and in 0000776.pdf (for every outline element, which looks like a
bug in the generator maybe) of 0000.zip from the pdfa dataset.
