update readme

README.md

@@ -1,6 +1,16 @@
 # PDF parser and renderer
 
-Early stage, focused only on well-formed input and Type 1 fonts
+An attempt at writing a PDF renderer from as close to scratch as possible.
+
+This project includes from-scratch parsers/interpreters/renderers/implementations of PostScript, ICC profiles, PNG compression, Type 1 fonts (.pfb files), TrueType fonts (.ttf files), CFF fonts, 2d path manipulation and rasterization, among others. 
+
+This library is intended to crash on malformed input and makes heavy use of assertions to ensure that parsing is never silently incorrect. 
+
+This library is not suited for the regular user, and has limited utility outside of the niche cases that I personally use it for.
+
+As a parser, this projects is the most comprehensive pure-rust implementation I am aware of, though as a renderer it is less complete.
+
+It should be noted that this library will intentionally deviate from the spec when there is the potential for network/disk access or RCE through PDF files. See https://web-in-security.blogspot.com/2021/01/insecure-features-in-pdfs.html for a good reference of just some of such features.
 
 ## Reading
 
@@ -12,18 +22,38 @@ https://adobe-type-tools.github.io/font-tech-notes/pdfs/T1_SPEC.pdf<br>
 http://www.libpng.org/pub/png/spec/1.2/png-1.2.pdf<br>
 https://www.adobe.com/content/dam/acom/en/devnet/postscript/pdfs/TN5603.Filters.pdf<br>
 https://www.adobe.com/content/dam/acom/en/devnet/actionscript/articles/psrefman.pdf<br>
+https://developer.apple.com/fonts/TrueType-Reference-Manual<br>
 https://hepunx.rl.ac.uk/~adye/psdocs/ref/REF.html<br>
 http://fileformats.archiveteam.org/wiki/PostScript_binary_object_format<br>
+https://adobe-type-tools.github.io/font-tech-notes/pdfs/5176.CFF.pdf<br>
+https://adobe-type-tools.github.io/font-tech-notes/pdfs/5177.Type2.pdf<br>
+https://www.color.org/icc1v42.pdf<br>
+https://adobe-type-tools.github.io/font-tech-notes/pdfs/5049.StemSnap.pdf<br>
+https://www.pdfa.org/norm-refs/5620.PortableJobTicket.pdf<br>
+https://www.itu.int/rec/T-REC-T.6-198811-I/en<br>
+
+##### True Type Resources
+
+https://www.truetype-typography.com/tthints.htm
+https://learn.microsoft.com/en-us/typography/opentype/spec/ttch01
+https://developer.apple.com/fonts/TrueType-Reference-Manual
+https://xgridfit.sourceforge.net/round.html
 
-### Algorithms
+### Algorithms and Relevant Literature
 
 http://members.chello.at/~easyfilter/Bresenham.pdf<br>
 https://en.wikipedia.org/wiki/Ascii85<br>
 https://pomax.github.io/bezierinfo<br>
 https://secure.math.ubc.ca/~cass/piscript/type1.pdf<br>
 https://ltr.wtf/explained/bidiintro.html<br>
+https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1000&context=facpub<br>
+https://raphlinus.github.io/graphics/curves/2019/12/23/flatten-quadbez.html<br>
+http://www.cccg.ca/proceedings/2004/36.pdf<br>
 
 ### Other resources
 
 https://speakerdeck.com/ange/lets-write-a-pdf-file<br>
 https://web.archive.org/web/20150110042057/http://home.comcast.net/~jk05/presentations/PDFTutorials.html/<br>
+http://formats.kaitai.io/ttf/ttf.svg/<br>
+https://www.tinaja.com/glib/interdic.pdf<br>
+https://personal.math.ubc.ca/~cass/piscript/type1.pdf<br>