The palettized codec. More...

#include <wowlib/formats/blp/codec.hpp>

Public Member Functions
	PaletteCodec (std::uint8_t alphaDepth) noexcept
std::size_t	encodedSize (std::uint32_t width, std::uint32_t height) const noexcept
	The exact payload size of a level: one index byte per pixel plus the packed alpha plane.
Result< std::vector< std::uint8_t > >	decode (std::span< const std::byte > src, std::span< const CImVector, BlpPaletteSize > palette, std::uint32_t width, std::uint32_t height) const
	Decode one level's index + alpha-plane payload to RGBA8 pixels.
Result< FileBuffer >	encode (std::span< const std::uint8_t > rgba, std::span< const CImVector, BlpPaletteSize > palette, std::uint32_t width, std::uint32_t height) const
	Encode RGBA8 pixels against an existing palette: nearest-entry indices plus the packed alpha plane, exactly encodedSize() bytes.
std::array< CImVector, BlpPaletteSize >	buildPalette (std::span< const std::uint8_t > rgba) const
	Build a 256-entry palette for an image (median-cut over the opaque RGB values; an image with <= 256 distinct colors gets them verbatim).

Protected Member Functions
std::uint8_t	_unpackAlpha (std::span< const std::byte > plane, std::size_t index) const noexcept
	The alpha value of texel index unpacked from the plane at this codec's bit depth (255 when the depth is 0).
void	_packAlpha (std::uint8_t alpha, std::span< std::byte > plane, std::size_t index) const noexcept
	Pack one texel's alpha into the plane at this codec's bit depth.

Static Protected Member Functions
static std::uint8_t	_nearestIndex (std::span< const CImVector, BlpPaletteSize > palette, std::uint8_t r, std::uint8_t g, std::uint8_t b) noexcept
	The palette entry nearest to (r, g, b) by squared RGB distance.

Detailed Description

The palettized codec.

Constructed with the alpha-plane bit depth (its state — 0, 1, 4 or 8 bits per pixel); decode() looks indices up in the 256-entry BGRX palette and unpacks the trailing alpha plane, encode() maps pixels to nearest palette entries and packs the plane. Palette construction (median-cut quantization) is its own verb so one palette serves every mip level.

Definition at line 135 of file codec.hpp.

Constructor & Destructor Documentation

◆ PaletteCodec()

wowlib::formats::blp::detail::PaletteCodec::PaletteCodec ( std::uint8_t alphaDepth )

inlineexplicitnoexcept

Parameters

alphaDepth the alpha plane's bits per pixel (0, 1, 4 or 8).

Definition at line 138 of file codec.hpp.

Member Function Documentation

◆ _nearestIndex()

std::uint8_t wowlib::formats::blp::detail::PaletteCodec::_nearestIndex	(	std::span< const CImVector, BlpPaletteSize >	palette,
		std::uint8_t	r,
		std::uint8_t	g,
		std::uint8_t	b )

staticprotectednoexcept

The palette entry nearest to (r, g, b) by squared RGB distance.

Parameters

palette	the color table.
r	the red value.
g	the green value.
b	the blue value.

Returns: the nearest entry's index.

Definition at line 358 of file blp.cpp.

References wowlib::formats::blp::BlpPaletteSize.

Referenced by encode().

◆ _packAlpha()

void wowlib::formats::blp::detail::PaletteCodec::_packAlpha	(	std::uint8_t	alpha,
		std::span< std::byte >	plane,
		std::size_t	index ) const

protectednoexcept

Pack one texel's alpha into the plane at this codec's bit depth.

Parameters

alpha	the 8-bit alpha value.
plane	the packed plane bytes (pre-sized, zero-filled).
index	the texel ordinal.

Definition at line 340 of file blp.cpp.

Referenced by encode().

◆ _unpackAlpha()

std::uint8_t wowlib::formats::blp::detail::PaletteCodec::_unpackAlpha	(	std::span< const std::byte >	plane,
		std::size_t	index ) const

protectednoexcept

The alpha value of texel index unpacked from the plane at this codec's bit depth (255 when the depth is 0).

Parameters

plane	the packed alpha plane bytes.
index	the texel ordinal.

Returns: the 8-bit alpha value.

Definition at line 320 of file blp.cpp.

Referenced by decode().

◆ buildPalette()

std::array< CImVector, BlpPaletteSize > wowlib::formats::blp::detail::PaletteCodec::buildPalette ( std::span< const std::uint8_t > rgba ) const

nodiscard

Build a 256-entry palette for an image (median-cut over the opaque RGB values; an image with <= 256 distinct colors gets them verbatim).

Parameters

rgba	the level-0 RGBA bytes.

Returns: the color table (unused tail entries zero).

Definition at line 419 of file blp.cpp.

References wowlib::formats::blp::BlpPaletteSize.

Referenced by wowlib::formats::blp::BLP::encode().

◆ decode()

Result< std::vector< std::uint8_t > > wowlib::formats::blp::detail::PaletteCodec::decode	(	std::span< const std::byte >	src,
		std::span< const CImVector, BlpPaletteSize >	palette,
		std::uint32_t	width,
		std::uint32_t	height ) const

nodiscard

Decode one level's index + alpha-plane payload to RGBA8 pixels.

Parameters

src	the on-disk payload bytes; short payloads decode their missing texels transparent black.
palette	the file's 256-entry color table.
width	the level width in pixels.
height	the level height in pixels.

Returns: width * height * 4 RGBA bytes.

Definition at line 377 of file blp.cpp.

References _unpackAlpha(), wowlib::formats::common::CImVector::b, wowlib::formats::common::CImVector::g, and wowlib::formats::common::CImVector::r.

Referenced by wowlib::formats::blp::BLP::decode().

◆ encode()

Result< FileBuffer > wowlib::formats::blp::detail::PaletteCodec::encode	(	std::span< const std::uint8_t >	rgba,
		std::span< const CImVector, BlpPaletteSize >	palette,
		std::uint32_t	width,
		std::uint32_t	height ) const

nodiscard

Encode RGBA8 pixels against an existing palette: nearest-entry indices plus the packed alpha plane, exactly encodedSize() bytes.

Parameters

rgba	width * height * 4 RGBA bytes.
palette	the color table to index into.
width	the level width in pixels.
height	the level height in pixels.

Returns: the payload bytes.

Definition at line 395 of file blp.cpp.

References _nearestIndex(), _packAlpha(), and encodedSize().

Referenced by wowlib::formats::blp::BLP::encode().

◆ encodedSize()

std::size_t wowlib::formats::blp::detail::PaletteCodec::encodedSize	(	std::uint32_t	width,
		std::uint32_t	height ) const

inlinenodiscardnoexcept

The exact payload size of a level: one index byte per pixel plus the packed alpha plane.

Parameters

width	the level width in pixels.
height	the level height in pixels.

Returns: the encoded byte count.

Definition at line 146 of file codec.hpp.

Referenced by encode().

The documentation for this class was generated from the following files:

src/wowlib/formats/blp/codec.hpp
src/wowlib/formats/blp/blp.cpp

Public Member Functions

Protected Member Functions

Static Protected Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ PaletteCodec()

Member Function Documentation

◆ _nearestIndex()

◆ _packAlpha()

◆ _unpackAlpha()

◆ buildPalette()

◆ decode()

◆ encode()

◆ encodedSize()