Namespaces
namespace	colors

namespace	DisplayOps
	Display operation constants.

namespace	Grayscale
	Bit manipulation constants for grayscale processing.

namespace	hal

namespace	internal

namespace	PanelConfig
	Panel configuration constants.

namespace	pixel_constants

namespace	PowerOptimization
	Power optimization register settings.

namespace	Resolution
	Resolution setting constants.

namespace	Timing
	Timing constants for EPD27 operations (in milliseconds).

Classes
struct	BoosterConfig
	Booster soft start configuration. More...

class	CircleBuilder

struct	CircleCommand
	Command for drawing a circle. More...

class	ColorManager

class	Device

struct	DeviceColor
	Device-specific color representation (generic template). More...

struct	DeviceColor< DisplayMode::BlackWhite >

struct	DeviceColor< DisplayMode::BWR >
	Specialization for Black/White/Red displays. More...

struct	DeviceColor< DisplayMode::BWY >
	Specialization for Black/White/Yellow displays. More...

struct	DeviceColor< DisplayMode::Grayscale4 >

struct	DeviceColor< DisplayMode::Spectra6 >
	Specialization for Spectra 6 (6-color) displays. More...

struct	DeviceConfig

class	Display

struct	driver_traits
	Driver capabilities trait template. More...

struct	driver_traits< EPD27 >

struct	driver_traits< MockDriver >

class	EPD27
	2.7 inch e-paper display driver (176x264 pixels). More...

struct	EPD27PinConfig
	Pin configuration for standard Raspberry Pi HATs. More...

struct	Error

class	Font

struct	FontMetrics
	Font dimension metrics. More...

class	Graphics

class	ImageIO
	Utilities for loading/saving images and converting formats. More...

class	LineBuilder

struct	LineCommand
	Command for drawing a line between two points. More...

struct	LineStyleSpec

class	MockDriver

class	MonoFramebuffer

class	MultiPlaneFramebuffer

class	Pin

struct	PinConfig
	Pin configuration tracking (internal use). More...

struct	Point

class	PointBuilder

struct	PointCommand
	Command for drawing a point (pixel or multi-pixel dot). More...

struct	PowerConfig
	Power configuration settings for EPD27. More...

class	RectangleBuilder

struct	RectangleCommand
	Command for drawing a rectangle. More...

struct	RGB

struct	RGBA

struct	ShapeStyleSpec

struct	Size

class	TextBuilder

struct	TextCommand
	Command for drawing text. More...

struct	TextStyleSpec

Concepts
concept	FramebufferLike

concept	DriverTraits
	Concept to check if a type is a valid driver with capabilities.

concept	Driver

Typedefs
using	TwoPlaneFramebuffer = MultiPlaneFramebuffer< internal::PlaneCount::Two >
	Convenience alias for a two-plane color framebuffer.

Enumerations
enum class	TriColor : std::uint8_t { Black = 0 , White = 1 , Third = 2 }
	Color values for 3-color displays (Black/White/Red or Black/White/Yellow). More...

enum class	Spectra6Color : std::uint8_t { Black = 0 , White = 1 , Red = 2 , Yellow = 3 , Blue = 4 , Green = 5 }
	Color values for Spectra 6 displays. More...

enum class	ErrorCode { DeviceNotInitialized , DeviceInitFailed , GPIOInitFailed , GPIORequestFailed , SPIInitFailed , SPIDeviceOpenFailed , SPIConfigFailed , InvalidPin , TransferFailed , DriverNotInitialized , DriverInitFailed , InvalidMode , Timeout , DisplayNotReady , RefreshFailed , FileNotFound , InvalidFormat , LoadFailed , InvalidDimensions }
	Unified error codes for all libepaper operations. More...

enum class	Color : std::uint8_t { White = 0xFF , Black = 0x00 , Gray1 = 0x80 , Gray2 = 0x40 , Red = 0x01 , Yellow = 0x02 , Blue = 0x03 , Green = 0x04 }

enum class	Orientation : std::uint8_t { Portrait0 = 0 , Landscape90 = 1 , Portrait180 = 2 , Landscape270 = 3 }

enum class	DotPixel : std::uint8_t { Pixel1x1 = 1 , Pixel2x2 = 2 , Pixel3x3 = 3 , Pixel4x4 = 4 , Pixel5x5 = 5 , Pixel6x6 = 6 , Pixel7x7 = 7 , Pixel8x8 = 8 }

enum class	LineStyle { Solid , Dotted }

enum class	DrawFill { Empty , Full }

enum class	TextContent { String , Number , Decimal }
	Content type for text rendering. More...

enum class	DisplayMode : std::uint8_t { BlackWhite , Grayscale4 , BWR , BWY , Spectra6 }

enum class	Command : std::uint8_t { BOOSTER_SOFT_START = 0x06 , DATA_START_TRANSMISSION_1 = 0x10 , DISPLAY_REFRESH = 0x12 , DATA_START_TRANSMISSION_2 = 0x13 , PARTIAL_DISPLAY_REFRESH = 0x16 , LUT_VCOM = 0x20 , LUT_WW = 0x21 , LUT_BW = 0x22 , LUT_WB = 0x23 , LUT_BB = 0x24 , LUT_WW2 = 0x25 , PLL_CONTROL = 0x30 , VCOM_DATA_INTERVAL = 0x50 , RESOLUTION_SETTING = 0x61 , GET_STATUS = 0x71 , VCM_DC_SETTING = 0x82 , POWER_OPTIMIZATION = 0xF8 , PANEL_SETTING = 0x00 , POWER_SETTING = 0x01 , POWER_OFF = 0x02 , POWER_ON = 0x04 , DEEP_SLEEP = 0x07 }
	E-paper display command codes for EPD27. More...

Functions
template<typename DriverType > requires Driver<DriverType> && DriverTraits<DriverType>
auto	create_display (Device &device, DisplayMode mode, Orientation orientation=Orientation::Portrait0, bool auto_sleep=true) -> std::expected< Display< DriverType, MonoFramebuffer >, Error >
	Convenience factory for mono-plane displays.

template<typename DriverType , FramebufferLike FramebufferT> requires Driver<DriverType> && DriverTraits<DriverType>
auto	create_display (Device &device, DisplayMode mode, Orientation orientation=Orientation::Portrait0, bool auto_sleep=true) -> std::expected< Display< DriverType, FramebufferT >, Error >
	Primary factory function for creating displays with explicit framebuffer type.

constexpr auto	to_string (ErrorCode code) -> std::string_view
	Convert error code to string representation.

auto	make_error (ErrorCode code, std::string_view context={}) -> Error

template<typename Driver > requires DriverTraits<Driver>
constexpr auto	supports_display_mode (DisplayMode mode) noexcept -> bool

constexpr auto	bits_per_pixel (DisplayMode mode) noexcept -> std::uint8_t
	Get bits per pixel for a display mode.

constexpr auto	is_color_mode (DisplayMode mode) noexcept -> bool
	Check if mode supports color (non-grayscale).

constexpr auto	num_planes (DisplayMode mode) noexcept -> std::size_t
	Get number of color planes required for a display mode.

constexpr auto	spectra6_color_to_value (Color color) noexcept -> std::uint8_t
	Convert a Color to its 3-bit Spectra6 value.

constexpr auto	spectra6_value_to_color (std::uint8_t value) noexcept -> Color
	Convert a 3-bit Spectra6 value to Color.

constexpr auto	color_to_rgb (Color color) noexcept -> RGB
	Convert a Color enum to RGB values.

constexpr auto	rgb_to_grayscale (std::uint8_t r, std::uint8_t g, std::uint8_t b) noexcept -> std::uint8_t
	Convert RGB values to grayscale using standard luminance formula.

constexpr auto	rgb_to_color_bw (std::uint8_t r, std::uint8_t g, std::uint8_t b) noexcept -> Color
	Convert RGB to Color for black/white mode.

constexpr auto	rgb_to_color_grayscale4 (std::uint8_t r, std::uint8_t g, std::uint8_t b) noexcept -> Color
	Convert RGB to Color for 4-level grayscale mode.

constexpr auto	rgb_to_color (DisplayMode mode, std::uint8_t r, std::uint8_t g, std::uint8_t b) noexcept -> Color
	Convert RGB to Color based on display mode.

constexpr auto	calculate_bw_position (std::size_t width, std::size_t x, std::size_t y) noexcept -> std::pair< std::size_t, std::uint8_t >
	Calculate byte index and bit mask for B/W mode pixel.

constexpr auto	calculate_gray_position (std::size_t width, std::size_t x, std::size_t y) noexcept -> std::pair< std::size_t, std::uint8_t >
	Calculate byte index and pixel shift for Grayscale4 mode pixel.

constexpr auto	calculate_spectra6_position (std::size_t width, std::size_t x, std::size_t y) noexcept -> std::pair< std::size_t, std::size_t >
	Calculate byte index and bit offset for Spectra6 (3-bit) mode pixel.

auto	get_pixel_bw (std::span< const std::byte > buffer, std::size_t width, std::size_t x, std::size_t y) noexcept -> Color
	Read a pixel from a B/W mode buffer.

auto	get_pixel_grayscale4 (std::span< const std::byte > buffer, std::size_t width, std::size_t x, std::size_t y) noexcept -> Color
	Read a pixel from a Grayscale4 mode buffer.

auto	get_pixel_bwr_bwy (std::span< const std::byte > buffer, std::size_t width, std::size_t height, std::size_t x, std::size_t y, bool is_bwr) noexcept -> Color
	Read a pixel from a BWR or BWY mode buffer.

auto	get_pixel_spectra6 (std::span< const std::byte > buffer, std::size_t width, std::size_t x, std::size_t y) noexcept -> Color
	Read a pixel from a Spectra6 mode buffer.

auto	get_pixel_from_buffer (DisplayMode mode, std::span< const std::byte > buffer, std::size_t width, std::size_t height, std::size_t x, std::size_t y) noexcept -> Color
	Read a pixel from a buffer based on display mode.

auto	set_pixel_bw (std::span< std::byte > buffer, std::size_t width, std::size_t x, std::size_t y, Color color) noexcept -> void
	Write a pixel to a B/W mode buffer.

auto	set_pixel_grayscale4 (std::span< std::byte > buffer, std::size_t width, std::size_t x, std::size_t y, Color color) noexcept -> void
	Write a pixel to a Grayscale4 mode buffer.

auto	set_pixel_bwr_bwy (std::span< std::byte > buffer, std::size_t width, std::size_t height, std::size_t x, std::size_t y, Color color, bool is_bwr) noexcept -> void
	Write a pixel to a BWR or BWY mode buffer.

auto	set_pixel_spectra6 (std::span< std::byte > buffer, std::size_t width, std::size_t x, std::size_t y, Color color) noexcept -> void
	Write a pixel to a Spectra6 mode buffer.

auto	set_pixel_in_buffer (DisplayMode mode, std::span< std::byte > buffer, std::size_t width, std::size_t height, std::size_t x, std::size_t y, Color color) noexcept -> void
	Write a pixel to a buffer based on display mode.

Variables
constexpr PowerConfig	POWER_CONFIG_BW
	Power configuration for black/white mode.

constexpr PowerConfig	POWER_CONFIG_GRAYSCALE
	Power configuration for grayscale mode.

constexpr BoosterConfig	BOOSTER_CONFIG = {.phase1 = 0x07, .phase2 = 0x07, .phase3 = 0x17}
	Standard booster soft start configuration.

constexpr std::array< Color, 8 >	SPECTRA6_VALUE_TO_COLOR
	Mapping from 3-bit Spectra6 value to Color enum.

Typedef Documentation

◆ TwoPlaneFramebuffer

using epaper::TwoPlaneFramebuffer = typedef MultiPlaneFramebuffer<internal::PlaneCount::Two>

Convenience alias for a two-plane color framebuffer.

Examples: /mnt/nas/libepaper/include/epaper/core/framebuffer.hpp.

Enumeration Type Documentation

◆ Color

enum class epaper::Color : std::uint8_t

strong

Enumerator
White	White (or lightest gray in grayscale modes)
Black	Black (or darkest gray in grayscale modes)
Gray1	First gray level - lighter (Grayscale4 mode only)
Gray2	Second gray level - darker (Grayscale4 mode only)
Red	Red (BWR and Spectra6 modes)
Yellow	Yellow (BWY and Spectra6 modes)
Blue	Blue (Spectra6 mode only)
Green	Green (Spectra6 mode only)

Examples: /mnt/nas/libepaper/include/epaper/color/color_manager.hpp, /mnt/nas/libepaper/include/epaper/core/display.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer_concepts.hpp, /mnt/nas/libepaper/include/epaper/core/types.hpp, /mnt/nas/libepaper/include/epaper/draw/builders.hpp, /mnt/nas/libepaper/include/epaper/draw/commands.hpp, /mnt/nas/libepaper/include/epaper/draw/styles.hpp, /mnt/nas/libepaper/include/epaper/graphics/graphics.hpp, and /mnt/nas/libepaper/include/epaper/io/image_io.hpp.

◆ Command

enum class epaper::Command : std::uint8_t

strong

E-paper display command codes for EPD27.

Enumerator
BOOSTER_SOFT_START	Booster soft start control.
DATA_START_TRANSMISSION_1	Start data transmission (old data)
DISPLAY_REFRESH	Refresh display.
DATA_START_TRANSMISSION_2	Start data transmission (new data)
PARTIAL_DISPLAY_REFRESH	Partial display refresh control.
LUT_VCOM	VCOM LUT register.
LUT_WW	White-to-White LUT register.
LUT_BW	Black-to-White LUT register.
LUT_WB	White-to-Black LUT register.
LUT_BB	Black-to-Black LUT register.
LUT_WW2	Additional White-to-White LUT register.
PLL_CONTROL	PLL control (frame rate)
VCOM_DATA_INTERVAL	VCOM and data interval setting.
RESOLUTION_SETTING	Resolution setting.
GET_STATUS	Get display status.
VCM_DC_SETTING	VCM DC setting.
POWER_OPTIMIZATION	Power optimization register.
PANEL_SETTING	Panel setting register.
POWER_SETTING	Power setting.
POWER_OFF	Power off command.
POWER_ON	Power on command.
DEEP_SLEEP	Deep sleep mode.

◆ DisplayMode

enum class epaper::DisplayMode : std::uint8_t

strong

Enumerator
BlackWhite	1-bit black and white (2 colors)
Grayscale4	2-bit 4-level grayscale
BWR	Black, White, Red (3 colors, typically 2-bit)
BWY	Black, White, Yellow (3 colors, typically 2-bit)
Spectra6	6-color: Black, White, Red, Yellow, Blue, Green (3-bit)

Examples: /mnt/nas/libepaper/include/epaper/color/device_color.hpp, /mnt/nas/libepaper/include/epaper/core/display.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer_concepts.hpp, /mnt/nas/libepaper/include/epaper/drivers/capabilities.hpp, /mnt/nas/libepaper/include/epaper/drivers/driver.hpp, /mnt/nas/libepaper/include/epaper/drivers/driver_concepts.hpp, and /mnt/nas/libepaper/include/epaper/drivers/mock_driver.hpp.

◆ DotPixel

enum class epaper::DotPixel : std::uint8_t

strong

Enumerator
Pixel1x1	Single pixel (finest resolution)
Pixel2x2	2x2 pixel block
Pixel3x3	3x3 pixel block
Pixel4x4	4x4 pixel block
Pixel5x5	5x5 pixel block
Pixel6x6	6x6 pixel block
Pixel7x7	7x7 pixel block
Pixel8x8	8x8 pixel block (thickest)

Examples: /mnt/nas/libepaper/include/epaper/core/types.hpp, /mnt/nas/libepaper/include/epaper/draw/builders.hpp, /mnt/nas/libepaper/include/epaper/draw/commands.hpp, and /mnt/nas/libepaper/include/epaper/draw/styles.hpp.

◆ DrawFill

enum class epaper::DrawFill

strong

Enumerator
Empty	Draw outline only (border with no fill)
Full	Draw filled shape (solid interior)

Examples: /mnt/nas/libepaper/include/epaper/core/types.hpp, /mnt/nas/libepaper/include/epaper/draw/builders.hpp, /mnt/nas/libepaper/include/epaper/draw/commands.hpp, /mnt/nas/libepaper/include/epaper/draw/styles.hpp, and /mnt/nas/libepaper/include/epaper/graphics/graphics.hpp.

◆ ErrorCode

enum class epaper::ErrorCode

strong

Unified error codes for all libepaper operations.

This enum consolidates all error types across the library, providing a consistent error handling interface.

Enumerator
DeviceNotInitialized	Device has not been initialized.
DeviceInitFailed	Device initialization failed.
GPIOInitFailed	GPIO initialization failed (libgpiod)
GPIORequestFailed	GPIO line request failed.
SPIInitFailed	SPI initialization failed.
SPIDeviceOpenFailed	SPI device open failed.
SPIConfigFailed	SPI configuration failed.
InvalidPin	Invalid GPIO pin number.
TransferFailed	SPI/data transfer failed.
DriverNotInitialized	Driver has not been initialized.
DriverInitFailed	Driver initialization failed.
InvalidMode	Invalid display mode specified.
Timeout	Operation timed out.
DisplayNotReady	Display is not ready for operation.
RefreshFailed	Display refresh operation failed.
FileNotFound	Image file not found.
InvalidFormat	Invalid or unsupported image format.
LoadFailed	Failed to load image data.
InvalidDimensions	Invalid image dimensions.

Examples: /mnt/nas/libepaper/include/epaper/core/errors.hpp.

◆ LineStyle

enum class epaper::LineStyle

strong

Enumerator
Solid	Continuous solid line.
Dotted	Dotted line pattern (alternating pixels)

Examples: /mnt/nas/libepaper/include/epaper/core/types.hpp, /mnt/nas/libepaper/include/epaper/draw/builders.hpp, /mnt/nas/libepaper/include/epaper/draw/commands.hpp, /mnt/nas/libepaper/include/epaper/draw/styles.hpp, and /mnt/nas/libepaper/include/epaper/graphics/graphics.hpp.

◆ Orientation

enum class epaper::Orientation : std::uint8_t

strong

Enumerator
Portrait0	Default portrait orientation (0° rotation)
Landscape90	90° clockwise rotation (landscape mode)
Portrait180	180° rotation (upside down portrait)
Landscape270	270° clockwise / 90° counter-clockwise (landscape mode)

Examples: /mnt/nas/libepaper/include/epaper/core/display.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer_concepts.hpp, /mnt/nas/libepaper/include/epaper/core/types.hpp, /mnt/nas/libepaper/include/epaper/graphics/graphics.hpp, and /mnt/nas/libepaper/include/epaper/internal/internal.hpp.

◆ Spectra6Color

enum class epaper::Spectra6Color : std::uint8_t

strong

Color values for Spectra 6 displays.

6-Color Palette:

Supports full primary and secondary colors in RGB space
Each color encoded as 3-bit value (0-5, values 6-7 unused)
Pixels packed tightly in framebuffer (may span byte boundaries)

Bit Encoding:

Color  | Value | Binary | RGB Equivalent
-------|-------|--------|---------------
Black  |   0   |  000   | (0, 0, 0)
White  |   1   |  001   | (255, 255, 255)
Red    |   2   |  010   | (255, 0, 0)
Yellow |   3   |  011   | (255, 255, 0)
Blue   |   4   |  100   | (0, 0, 255)
Green  |   5   |  101   | (0, 255, 0)

Note: Spectra6 uses single-plane 3bpp encoding, unlike BWR/BWY dual-plane.

Enumerator
Black
White
Red
Yellow
Blue
Green

Examples: /mnt/nas/libepaper/include/epaper/color/device_color.hpp.

◆ TextContent

enum class epaper::TextContent

strong

Content type for text rendering.

Discriminant for TextCommand's internal union-like behavior. Determines which fields are active and how text is populated.

Enumerator
String	Direct string content (text field used as-is)
Number	Integer number (number field converted to text via sprintf)
Decimal	Decimal number (decimal field formatted with decimal_places precision)

Examples: /mnt/nas/libepaper/include/epaper/draw/builders.hpp, and /mnt/nas/libepaper/include/epaper/draw/commands.hpp.

◆ TriColor

enum class epaper::TriColor : std::uint8_t

strong

Color values for 3-color displays (Black/White/Red or Black/White/Yellow).

Used by BWR and BWY display modes which employ dual-plane architecture:

Plane 0: Black/White data (1 bpp)
Plane 1: Accent color data (1 bpp)

Dual-Plane Encoding:

Color   | Plane 0 | Plane 1 | TriColor Value
--------|---------|---------|---------------
Black   |    1    |    1    | Black (0)
White   |    0    |    1    | White (1)
Red/Yel |    0    |    0    | Third (2)

Note: The Third value represents Red for BWR mode and Yellow for BWY mode.

Enumerator
Black
White
Third	Red for BWR, Yellow for BWY.

Examples: /mnt/nas/libepaper/include/epaper/color/device_color.hpp.

Function Documentation

◆ bits_per_pixel()

constexpr auto epaper::bits_per_pixel ( DisplayMode mode ) -> std::uint8_t

constexprnoexcept

Get bits per pixel for a display mode.

Parameters

mode	Display mode

Returns: Bits per pixel required for this mode

Examples: /mnt/nas/libepaper/include/epaper/drivers/driver.hpp, and /mnt/nas/libepaper/include/epaper/drivers/mock_driver.hpp.

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◆ calculate_bw_position()

constexpr auto epaper::calculate_bw_position	(	std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> std::pair<std::size_t, std::uint8_t>

constexprnoexcept

Calculate byte index and bit mask for B/W mode pixel.

Encoding:

8 pixels per byte, MSB-first (leftmost pixel = bit 7)
Row-major layout: pixels packed left-to-right, top-to-bottom
Partial bytes: right-padded with zeros if width not multiple of 8

Example (width=10):

Pixels: [0][1][2][3][4][5][6][7] | [8][9][pad][pad]...

Byte 0: b7 b6 b5 b4 b3 b2 b1 b0 | Byte 1: b7 b6 ...

Parameters

width	Display width in pixels
x	X coordinate (0-based, left edge = 0)
y	Y coordinate (0-based, top edge = 0)

Returns: Pair of (byte_index, bit_mask) where bit_mask has single bit set

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◆ calculate_gray_position()

constexpr auto epaper::calculate_gray_position	(	std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> std::pair<std::size_t, std::uint8_t>

constexprnoexcept

Calculate byte index and pixel shift for Grayscale4 mode pixel.

Encoding:

2 bits per pixel, 4 pixels per byte
Packed MSB-first: pixel 0 in bits [7:6], pixel 1 in bits [5:4], etc.
4 gray levels: 00=Black, 01=Gray2 (dark), 10=Gray1 (light), 11=White

Example (width=6):

Pixels: [0][1][2][3] | [4][5][pad][pad]

Byte 0: [76][54][32][10] | Byte 1: [76][54][--][--]

Pixel shift values:

x % 4 == 0: shift = 0 (bits [7:6])
x % 4 == 1: shift = 2 (bits [5:4])
x % 4 == 2: shift = 4 (bits [3:2])
x % 4 == 3: shift = 6 (bits [1:0])

Parameters

width	Display width in pixels
x	X coordinate
y	Y coordinate

Returns: Pair of (byte_index, pixel_shift)

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◆ calculate_spectra6_position()

constexpr auto epaper::calculate_spectra6_position	(	std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> std::pair<std::size_t, std::size_t>

constexprnoexcept

Calculate byte index and bit offset for Spectra6 (3-bit) mode pixel.

Encoding:

3 bits per pixel (values 0-5 for 6 colors, 6-7 unused)
Pixels packed sequentially across byte boundaries
No alignment - pixel N starts at bit (N * 3) from buffer start

Example (first 3 pixels = 9 bits):

Pixel:   [  0  ][  1  ][  2  ]
Bits:    210 210 210
Byte 0:  [76543210] (contains p0 + p1_b2)
Byte 1:  [76543210] (contains p1_b1b0 + p2)

Cross-byte handling:

bit_offset ≤ 5: pixel fits in single byte
bit_offset > 5: pixel spans two bytes (need to merge bits)

Parameters

width	Display width in pixels
x	X coordinate
y	Y coordinate

Returns: Pair of (byte_index, bit_offset within byte)

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◆ color_to_rgb()

constexpr auto epaper::color_to_rgb ( Color color ) -> RGB

constexprnoexcept

Convert a Color enum to RGB values.

Parameters

color The e-paper color

Returns: RGB struct with red, green, blue components

Examples: /mnt/nas/libepaper/include/epaper/drivers/mock_driver.hpp.

◆ create_display() [1/2]

template<typename DriverType , FramebufferLike FramebufferT>
requires Driver<DriverType> && DriverTraits<DriverType>

auto epaper::create_display	(	Device &	device,
		DisplayMode	mode,
		Orientation	orientation = `Orientation::Portrait0`,
		bool	auto_sleep = `true`
	)		-> std::expected<Display<DriverType, FramebufferT>, Error>

Primary factory function for creating displays with explicit framebuffer type.

Template Parameters

DriverType	The driver type to use
FramebufferT	Framebuffer type to use

Parameters

device	Initialized device
mode	Display mode
orientation	Display orientation
auto_sleep	Enable auto-sleep after refresh

Returns: Display with the requested framebuffer type on success, Error on failure

◆ create_display() [2/2]

template<typename DriverType >
requires Driver<DriverType> && DriverTraits<DriverType>

auto epaper::create_display	(	Device &	device,
		DisplayMode	mode,
		Orientation	orientation = `Orientation::Portrait0`,
		bool	auto_sleep = `true`
	)		-> std::expected<Display<DriverType, MonoFramebuffer>, Error>

Convenience factory for mono-plane displays.

Defaults to MonoFramebuffer and validates that the requested mode is single-plane.

Template Parameters

DriverType The driver type to use

Parameters

device	Initialized device
mode	Display mode
orientation	Display orientation
auto_sleep	Enable auto-sleep after refresh

Returns: Display with a MonoFramebuffer on success, Error on failure

Examples: /mnt/nas/libepaper/include/epaper/core/display.hpp.

◆ get_pixel_bw()

auto epaper::get_pixel_bw	(	std::span< const std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> Color

inlinenoexcept

Read a pixel from a B/W mode buffer.

Bit Transformation:

Calculate byte index and bit mask (MSB-first)
Read byte from buffer
AND byte with bit_mask
Non-zero result = White (1), zero result = Black (0)

Safety:

Returns Color::White if byte_index out of bounds
No undefined behavior on invalid coordinates

Parameters

buffer	Framebuffer data (read-only)
width	Display width
x	X coordinate
y	Y coordinate

Returns: Color::White or Color::Black

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◆ get_pixel_bwr_bwy()

auto epaper::get_pixel_bwr_bwy	(	std::span< const std::byte >	buffer,
		std::size_t	width,
		std::size_t	height,
		std::size_t	x,
		std::size_t	y,
		bool	is_bwr
	)		-> Color

inlinenoexcept

Read a pixel from a BWR or BWY mode buffer.

Dual-Plane Encoding:

Buffer layout: [BW plane (plane_size bytes)][Color plane (plane_size bytes)]
Each plane: 1bpp, same layout as BlackWhite mode

Bit Transformation:

Read BW plane bit: 1 = candidate for white/color, 0 = candidate for black/color
Read Color plane bit: 0 = use color ink (active-low), 1 = no color ink
Decode combination:
- (BW=1, Color=1) → White (no ink on either plane)
- (BW=0, Color=1) → Black (BW ink only)
- (BW=x, Color=0) → Red/Yellow (color ink overwrites BW)

Active-Low Color Plane: E-paper color planes typically use inverted logic where 0 = "apply color ink". This allows white to be the default (all 1s).

Safety:

Returns Color::White if out of bounds
Validates both plane accesses

Parameters

buffer	Framebuffer data (two planes: B/W + color)
width	Display width
height	Display height (needed to calculate plane_size)
x	X coordinate
y	Y coordinate
is_bwr	True for BWR mode (Red), false for BWY mode (Yellow)

Returns: Color::White, Color::Black, Color::Red, or Color::Yellow

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◆ get_pixel_from_buffer()

auto epaper::get_pixel_from_buffer	(	DisplayMode	mode,
		std::span< const std::byte >	buffer,
		std::size_t	width,
		std::size_t	height,
		std::size_t	x,
		std::size_t	y
	)		-> Color

inlinenoexcept

Read a pixel from a buffer based on display mode.

Dispatches to the appropriate mode-specific function.

Parameters

mode	Display mode
buffer	Framebuffer data
width	Display width
height	Display height (needed for multi-plane modes)
x	X coordinate
y	Y coordinate

Returns: Pixel color

Examples: /mnt/nas/libepaper/include/epaper/drivers/mock_driver.hpp.

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◆ get_pixel_grayscale4()

auto epaper::get_pixel_grayscale4	(	std::span< const std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> Color

inlinenoexcept

Read a pixel from a Grayscale4 mode buffer.

Bit Transformation:

Calculate byte index and pixel shift (2 bits per pixel)
Read byte from buffer
Right-shift by (6 - pixel_shift) to align 2-bit field to LSBs
Mask with 0x03 to extract 2-bit value
Map 2-bit value to Color:
- 0b00 (0) → Black
- 0b01 (1) → Gray2 (dark gray)
- 0b10 (2) → Gray1 (light gray)
- 0b11 (3) → White

Safety:

Returns Color::White if byte_index out of bounds

Parameters

buffer	Framebuffer data (read-only)
width	Display width
x	X coordinate
y	Y coordinate

Returns: One of the four grayscale Color values

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◆ get_pixel_spectra6()

auto epaper::get_pixel_spectra6	(	std::span< const std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y
	)		-> Color

inlinenoexcept

Read a pixel from a Spectra6 mode buffer.

3-Bit Cross-Byte Decoding:

Pixel N spans bits [(N*3) : (N*3 + 2)] in buffer
May require reading 1 or 2 bytes depending on alignment

Case 1: Single-byte (bit_offset ≤ 5):

Byte:  [76543210]
        ^^^       3-bit pixel fits in one byte
Shift right by (5 - bit_offset), mask with 0x07

Case 2: Cross-byte (bit_offset = 6 or 7):

Byte N:   [......10]  (high_bits = 2 or 1)
Byte N+1: [1.......]  (low_bits = 1 or 2)
Merge: (high_byte & mask) << low_bits | (low_byte >> shift) & mask

Color Mapping: 0=Black, 1=White, 2=Red, 3=Yellow, 4=Blue, 5=Green, 6-7=Fallback to Black

Safety:

Returns Color::White if byte_index out of bounds
Handles partial second byte gracefully

Parameters

buffer	Framebuffer data (read-only)
width	Display width
x	X coordinate
y	Y coordinate

Returns: One of the six Spectra6 colors

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◆ is_color_mode()

constexpr auto epaper::is_color_mode ( DisplayMode mode ) -> bool

constexprnoexcept

Check if mode supports color (non-grayscale).

Parameters

mode	Display mode

Returns: true if mode supports color

Examples: /mnt/nas/libepaper/include/epaper/core/display.hpp, and /mnt/nas/libepaper/include/epaper/drivers/driver.hpp.

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◆ make_error()

auto epaper::make_error	(	ErrorCode	code,
		std::string_view	context = `{}`
	)		-> Error

inline

Examples: /mnt/nas/libepaper/include/epaper/core/errors.hpp.

◆ num_planes()

constexpr auto epaper::num_planes ( DisplayMode mode ) -> std::size_t

constexprnoexcept

Get number of color planes required for a display mode.

Parameters

mode	Display mode

Returns: Number of planes (1 for monochrome/grayscale, 2+ for color)

Examples: /mnt/nas/libepaper/include/epaper/core/display.hpp, /mnt/nas/libepaper/include/epaper/core/framebuffer.hpp, and /mnt/nas/libepaper/include/epaper/drivers/driver.hpp.

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◆ rgb_to_color()

constexpr auto epaper::rgb_to_color	(	DisplayMode	mode,
		std::uint8_t	r,
		std::uint8_t	g,
		std::uint8_t	b
	)		-> Color

constexprnoexcept

Convert RGB to Color based on display mode.

Parameters

mode	Current display mode
r	Red component
g	Green component
b	Blue component

Returns: Appropriate Color for the display mode

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◆ rgb_to_color_bw()

constexpr auto epaper::rgb_to_color_bw	(	std::uint8_t	r,
		std::uint8_t	g,
		std::uint8_t	b
	)		-> Color

constexprnoexcept

Convert RGB to Color for black/white mode.

Uses threshold of 128 for binarization.

Parameters

r	Red component
g	Green component
b	Blue component

Returns: Color::White or Color::Black

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◆ rgb_to_color_grayscale4()

constexpr auto epaper::rgb_to_color_grayscale4	(	std::uint8_t	r,
		std::uint8_t	g,
		std::uint8_t	b
	)		-> Color

constexprnoexcept

Convert RGB to Color for 4-level grayscale mode.

Quantizes to 4 levels: White, Gray1, Gray2, Black.

Parameters

r	Red component
g	Green component
b	Blue component

Returns: One of the four grayscale Color values

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◆ rgb_to_grayscale()

constexpr auto epaper::rgb_to_grayscale	(	std::uint8_t	r,
		std::uint8_t	g,
		std::uint8_t	b
	)		-> std::uint8_t

constexprnoexcept

Convert RGB values to grayscale using standard luminance formula.

Uses the ITU-R BT.601 luma formula: Y = 0.299R + 0.587G + 0.114B

Parameters

r	Red component (0-255)
g	Green component (0-255)
b	Blue component (0-255)

Returns: Grayscale value (0-255)

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◆ set_pixel_bw()

auto epaper::set_pixel_bw	(	std::span< std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y,
		Color	color
	)		-> void

inlinenoexcept

Write a pixel to a B/W mode buffer.

Bit Transformation:

Calculate byte index and bit mask (single bit set)
Read current byte value
For White: OR byte with bit_mask (set bit to 1)
For Black: AND byte with ~bit_mask (clear bit to 0)
Write modified byte back

Read-Modify-Write: Must preserve other 7 bits in the byte. Using bitwise operations ensures atomic semantics on single-threaded systems.

Safety:

No-op if byte_index out of bounds (silent fail)
Treats all non-White colors as Black

Parameters

buffer	Framebuffer data (mutable)
width	Display width
x	X coordinate
y	Y coordinate
color	Pixel color (White or Black)

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◆ set_pixel_bwr_bwy()

auto epaper::set_pixel_bwr_bwy	(	std::span< std::byte >	buffer,
		std::size_t	width,
		std::size_t	height,
		std::size_t	x,
		std::size_t	y,
		Color	color,
		bool	is_bwr
	)		-> void

inlinenoexcept

Write a pixel to a BWR or BWY mode buffer.

Dual-Plane Encoding Logic:

Input Color → (BW plane bit, Color plane bit)
White       → (1, 1)  # No ink on either plane
Black       → (0, 1)  # BW ink only
Red/Yellow  → (0, 0)  # Color ink (active-low)

Bit Transformation:

Calculate byte index and bit mask (same for both planes)
Decode input color to (is_bw_white, is_color) flags
Write BW plane: set bit if is_bw_white, clear otherwise
Write Color plane: clear bit if is_color (active-low!), set otherwise

Active-Low Color Logic: The Color plane bit is INVERTED:

0 = "apply color ink" (Red/Yellow pixel)
1 = "no color ink" (allows BW plane to show through)

Safety:

No-op if either plane access out of bounds
Validates buffer size includes both planes

Parameters

buffer	Framebuffer data (mutable, two planes)
width	Display width
height	Display height (for plane_size calculation)
x	X coordinate
y	Y coordinate
color	Pixel color
is_bwr	True for BWR mode (Red), false for BWY mode (Yellow)

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◆ set_pixel_grayscale4()

auto epaper::set_pixel_grayscale4	(	std::span< std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y,
		Color	color
	)		-> void

inlinenoexcept

Write a pixel to a Grayscale4 mode buffer.

Bit Transformation:

Calculate byte index and pixel shift (2 bits per pixel)
Extract 2-bit color value from Color enum (bits [7:6])
Shift color value right by pixel_shift to align with target position
Create mask for 2-bit field: 0xC0 >> pixel_shift
Clear target field: byte & ~mask
Set new value: (byte & ~mask) | (color_bits & mask)

Color Encoding:

Color enum already has correct bit patterns in [7:6]:
- Black = 0b00xx_xxxx → 0b00
- Gray2 = 0b01xx_xxxx → 0b01
- Gray1 = 0b10xx_xxxx → 0b10
- White = 0b11xx_xxxx → 0b11

Safety:

No-op if byte_index out of bounds
Preserves other 3 pixels in the byte

Parameters

buffer	Framebuffer data (mutable)
width	Display width
x	X coordinate
y	Y coordinate
color	Pixel color (one of 4 grayscale levels)

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◆ set_pixel_in_buffer()

auto epaper::set_pixel_in_buffer	(	DisplayMode	mode,
		std::span< std::byte >	buffer,
		std::size_t	width,
		std::size_t	height,
		std::size_t	x,
		std::size_t	y,
		Color	color
	)		-> void

inlinenoexcept

Write a pixel to a buffer based on display mode.

Dispatches to the appropriate mode-specific function.

Parameters

mode	Display mode
buffer	Framebuffer data (mutable)
width	Display width
height	Display height (needed for multi-plane modes)
x	X coordinate
y	Y coordinate
color	Pixel color

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◆ set_pixel_spectra6()

auto epaper::set_pixel_spectra6	(	std::span< std::byte >	buffer,
		std::size_t	width,
		std::size_t	x,
		std::size_t	y,
		Color	color
	)		-> void

inlinenoexcept

Write a pixel to a Spectra6 mode buffer.

Parameters

buffer	Framebuffer data (mutable)
width	Display width
x	X coordinate
y	Y coordinate
color	Pixel color

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◆ spectra6_color_to_value()

constexpr auto epaper::spectra6_color_to_value ( Color color ) -> std::uint8_t

constexprnoexcept

Convert a Color to its 3-bit Spectra6 value.

Parameters

color The color to convert

Returns: 3-bit value (0-5) for Spectra6 encoding

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◆ spectra6_value_to_color()

constexpr auto epaper::spectra6_value_to_color ( std::uint8_t value ) -> Color

constexprnoexcept

Convert a 3-bit Spectra6 value to Color.

Parameters

value 3-bit value (0-7)

Returns: Corresponding Color enum value

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◆ supports_display_mode()

template<typename Driver >
requires DriverTraits<Driver>

constexpr auto epaper::supports_display_mode ( DisplayMode mode ) -> bool

constexprnoexcept

Examples: /mnt/nas/libepaper/include/epaper/drivers/capabilities.hpp.

◆ to_string()

constexpr auto epaper::to_string ( ErrorCode code ) -> std::string_view

constexpr

Convert error code to string representation.

Parameters

code	Error code to convert

Returns: String view describing the error

Examples: /mnt/nas/libepaper/include/epaper/core/errors.hpp.

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Variable Documentation

◆ BOOSTER_CONFIG

constexpr BoosterConfig epaper::BOOSTER_CONFIG = {.phase1 = 0x07, .phase2 = 0x07, .phase3 = 0x17}

constexpr

Standard booster soft start configuration.

◆ POWER_CONFIG_BW

constexpr PowerConfig epaper::POWER_CONFIG_BW

constexpr

Initial value:

= {

.vds_en_vdg_en = 0x03, .vcom_hv_vghl_lv = 0x00, .vdh = 0x2B, .vdl = 0x2B, .vdhr = 0x09}

Power configuration for black/white mode.

◆ POWER_CONFIG_GRAYSCALE

constexpr PowerConfig epaper::POWER_CONFIG_GRAYSCALE

constexpr

Initial value:

= {
    .vds_en_vdg_en = 0x03,
    .vcom_hv_vghl_lv = 0x00,
    .vdh = 0x2B,
    .vdl = 0x2B,
    .vdhr = 0x00 
}

Power configuration for grayscale mode.

◆ SPECTRA6_VALUE_TO_COLOR

constexpr std::array<Color, 8> epaper::SPECTRA6_VALUE_TO_COLOR

constexpr

Initial value:

= {{
    Color::Black,  
    Color::White,  
    Color::Red,    
    Color::Yellow, 
    Color::Blue,   
    Color::Green,  
    Color::Black,  
    Color::Black   
}}

Mapping from 3-bit Spectra6 value to Color enum.

Namespaces

Classes

Concepts

Typedefs

Enumerations

Functions

Variables

Typedef Documentation

◆ TwoPlaneFramebuffer

Enumeration Type Documentation

◆ Color

◆ Command

◆ DisplayMode

◆ DotPixel

◆ DrawFill

◆ ErrorCode

◆ LineStyle

◆ Orientation

◆ Spectra6Color

◆ TextContent

◆ TriColor

Function Documentation

◆ bits_per_pixel()

◆ calculate_bw_position()

◆ calculate_gray_position()

◆ calculate_spectra6_position()

◆ color_to_rgb()

◆ create_display() [1/2]

◆ create_display() [2/2]

◆ get_pixel_bw()

◆ get_pixel_bwr_bwy()

◆ get_pixel_from_buffer()

◆ get_pixel_grayscale4()

◆ get_pixel_spectra6()

◆ is_color_mode()

◆ make_error()

◆ num_planes()

◆ rgb_to_color()

◆ rgb_to_color_bw()

◆ rgb_to_color_grayscale4()

◆ rgb_to_grayscale()

◆ set_pixel_bw()

◆ set_pixel_bwr_bwy()

◆ set_pixel_grayscale4()

◆ set_pixel_in_buffer()

◆ set_pixel_spectra6()

◆ spectra6_color_to_value()

◆ spectra6_value_to_color()

◆ supports_display_mode()

◆ to_string()

Variable Documentation

◆ BOOSTER_CONFIG

◆ POWER_CONFIG_BW

◆ POWER_CONFIG_GRAYSCALE

◆ SPECTRA6_VALUE_TO_COLOR