doc/spec/nie-related-work.md - external/github.com/google/wuffs - Git at Google

 # Naïve Image Formats (NIE, NII, NIA) Related Work

 This is a companion document to the [Naïve Image Formats (NIE, NII, NIA)
 Specification](/doc/spec/nie-spec.md). Its contents aren't necessary for
 implementing the NIE file format, but gives further context on what NIE is and
 is not.

 In general, being uncompressed, NIE/NII/NIA is not intended for long term
 storage or for delivery over a network. Alternative lossless image formats like
 [PNG](https://www.w3.org/TR/2003/REC-PNG-20031110/) or [WebP
 Lossless](https://developers.google.com/speed/webp/docs/riff_container) are far
 more suitable.

 Amongst uncompressed formats, [Farbfeld](https://tools.suckless.org/farbfeld/)
 is a very similar design. The main difference is that NIE is little-endian (the
 same as the vast majority of CPUs) where Farbfeld is big-endian. NIE/NII/NIA
 also allows animated images, not just still images, and is also configurable:
 non-premultiplied versus premultiplied alpha and 8- versus 16-bit channels.
 Configurability is admittedly a trade-off. One person's configuration parameter
 is another person's unnecessary bloat. We're not saying that Farbfeld is a bad
 design, just a different design that has chosen different trade-offs.

 [PAM](http://netpbm.sourceforge.net/doc/pam.html) (Portable Arbitrary Map) and
 its related formats (PBM, PGM, PPM) are also very similar. The main difference
 is that their headers are ASCII text and of variable length. Such headers are
 easier for humans to read but harder for computers to parse. Again, NIE/NII/NIA
 also allows animated images. Some programs process concatenated streams of PAM
 images as an animation, but that doesn't contain explicit timing information.

 [VIPS](https://jcupitt.github.io/libvips/API/current/file-format.html) is the
 intermediate format for the [libvips](https://libvips.github.io/libvips/) image
 processing library. Pixel data is stored in a straightforward fashion, but
 metadata is stored as XML, which is not simple, and is a potential security
 concern.

 Amongst flexible formats,
 [BMP](https://www.fileformat.info/format/bmp/egff.htm),
 [PNG](https://www.w3.org/TR/2003/REC-PNG-20031110/) and its animated variant
 [APNG](https://wiki.mozilla.org/APNG_Specification),
 [Targa](http://tfc.duke.free.fr/coding/tga_specs.pdf) and
 [TIFF](http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf) all have
 their built-in compression being optional. Some of those uncompressed forms
 have been used as simple interchange formats. Compared to those, NIE has fewer
 features, which is obviously unfavorable if you want such features, but can be
 favorable if you prefer simplicity and code auditability. A NIE file is still
 simpler than an uncompressed BMP file and a NIA file is still simpler than an
 uncompressed APNG file.

 For example, when using a sandboxed worker process to convert to an
 intermediate format, we don't want to use "all possible valid TIFF images" as
 the intermediate format, because a compromised worker process could generate a
 malicious intermediate image that provoked a security bug in an unsandboxed
 TIFF decoder. Instead, we would want only a very simple subset of TIFF, but it
 can be easier (in terms of implementation and in terms of a code audit) to
 write an (almost trivial) NIE parser from scratch instead of whittling down a
 full-featured TIFF library and hoping that you've eliminated all the potential
 security vulnerabilities.
	# Naïve Image Formats (NIE, NII, NIA) Related Work

	This is a companion document to the [Naïve Image Formats (NIE, NII, NIA)
	Specification](/doc/spec/nie-spec.md). Its contents aren't necessary for
	implementing the NIE file format, but gives further context on what NIE is and
	is not.

	In general, being uncompressed, NIE/NII/NIA is not intended for long term
	storage or for delivery over a network. Alternative lossless image formats like
	[PNG](https://www.w3.org/TR/2003/REC-PNG-20031110/) or [WebP
	Lossless](https://developers.google.com/speed/webp/docs/riff_container) are far
	more suitable.

	Amongst uncompressed formats, [Farbfeld](https://tools.suckless.org/farbfeld/)
	is a very similar design. The main difference is that NIE is little-endian (the
	same as the vast majority of CPUs) where Farbfeld is big-endian. NIE/NII/NIA
	also allows animated images, not just still images, and is also configurable:
	non-premultiplied versus premultiplied alpha and 8- versus 16-bit channels.
	Configurability is admittedly a trade-off. One person's configuration parameter
	is another person's unnecessary bloat. We're not saying that Farbfeld is a bad
	design, just a different design that has chosen different trade-offs.

	[PAM](http://netpbm.sourceforge.net/doc/pam.html) (Portable Arbitrary Map) and
	its related formats (PBM, PGM, PPM) are also very similar. The main difference
	is that their headers are ASCII text and of variable length. Such headers are
	easier for humans to read but harder for computers to parse. Again, NIE/NII/NIA
	also allows animated images. Some programs process concatenated streams of PAM
	images as an animation, but that doesn't contain explicit timing information.

	[VIPS](https://jcupitt.github.io/libvips/API/current/file-format.html) is the
	intermediate format for the [libvips](https://libvips.github.io/libvips/) image
	processing library. Pixel data is stored in a straightforward fashion, but
	metadata is stored as XML, which is not simple, and is a potential security
	concern.

	Amongst flexible formats,
	[BMP](https://www.fileformat.info/format/bmp/egff.htm),
	[PNG](https://www.w3.org/TR/2003/REC-PNG-20031110/) and its animated variant
	[APNG](https://wiki.mozilla.org/APNG_Specification),
	[Targa](http://tfc.duke.free.fr/coding/tga_specs.pdf) and
	[TIFF](http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf) all have
	their built-in compression being optional. Some of those uncompressed forms
	have been used as simple interchange formats. Compared to those, NIE has fewer
	features, which is obviously unfavorable if you want such features, but can be
	favorable if you prefer simplicity and code auditability. A NIE file is still
	simpler than an uncompressed BMP file and a NIA file is still simpler than an
	uncompressed APNG file.

	For example, when using a sandboxed worker process to convert to an
	intermediate format, we don't want to use "all possible valid TIFF images" as
	the intermediate format, because a compromised worker process could generate a
	malicious intermediate image that provoked a security bug in an unsandboxed
	TIFF decoder. Instead, we would want only a very simple subset of TIFF, but it
	can be easier (in terms of implementation and in terms of a code audit) to
	write an (almost trivial) NIE parser from scratch instead of whittling down a
	full-featured TIFF library and hoping that you've eliminated all the potential
	security vulnerabilities.