vtfpp::DistanceMapping Namespace Reference

Namespaces
namespace	detail

Enumerations
enum class	Dither { NONE = 0 , GRADIENT_TANGENT }
enum class	Flags : uint32_t { NONE = 0 , DISTANCEAA = 1 << 0 , EUCLIDEAN = 1 << 1 , SAMPLECENTERED = 1 << 2 }

Functions
std::vector< std::byte >	alphaToDistance (std::span< const std::byte > imageData, ImageFormat inFormat, ImageFormat outFormat, uint16_t width, uint16_t height, uint16_t reduceX, uint16_t reduceY, bool srgb, float distanceSpread=1.f, float alphaThreshold=0.04f, Flags flags=Flags::NONE, Dither dither=Dither::NONE, ImageConversion::ResizeFilter filter=ImageConversion::ResizeFilter::NICE, ImageConversion::ResizeEdge edge=ImageConversion::ResizeEdge::CLAMP, bool *valveQuirks=nullptr)
	In one operation, convert an image's alpha channel, or, for single-channel formats, its only channel, to a VTEX-style distance map, and downscale other channels, if present in the output, according to the given resize parameters.

Enumeration Type Documentation

Dither

enum class vtfpp::DistanceMapping::Dither

strong

Enumerator
NONE	No dithering.
GRADIENT_TANGENT	Experimental dithering approach that diffuses quantization error perpendicular to the distance gradient at any destination pixel. Slow and requires up to double the memory.

Definition at line 10 of file DistanceMapping.h.

Flags

enum class vtfpp::DistanceMapping::Flags : uint32_t

strong

Enumerator
NONE
DISTANCEAA	Experimental; interpret the alpha channel as antialiased. Can result in a more precise distance map, but produces nonsense if large gradients are present.
EUCLIDEAN	The distance-mapping algorithm is a brute-force scan of a square area. If this is enabled, only accept distance hits in a circular area.
SAMPLECENTERED	Search from the center of pixels (in destination coordinate space) rather than in their north-west corners. Can mitigate a perceived southeast shift at extreme reductions.

Definition at line 16 of file DistanceMapping.h.

Function Documentation

alphaToDistance()

std::vector< std::byte > vtfpp::DistanceMapping::alphaToDistance ( std::span< const std::byte > imageData, ImageFormat inFormat, ImageFormat outFormat, uint16_t width, uint16_t height, uint16_t reduceX, uint16_t reduceY, bool srgb, float distanceSpread = 1.f, float alphaThreshold = 0.04f, DistanceMapping::Flags flags = Flags::NONE, DistanceMapping::Dither dither = Dither::NONE, ImageConversion::ResizeFilter filter = ImageConversion::ResizeFilter::NICE, ImageConversion::ResizeEdge edge = ImageConversion::ResizeEdge::CLAMP, bool * valveQuirks = nullptr )

nodiscard

In one operation, convert an image's alpha channel, or, for single-channel formats, its only channel, to a VTEX-style distance map, and downscale other channels, if present in the output, according to the given resize parameters.

Returns

Empty if:

• inFormat or outFormat do not satisfy their documented predicates,
• reduceX or reduceY are not powers of two,
• distanceSpread would result in a search radius of zero with either reduceX or reduceY,
• alphaThreshold is out of range, or
• edge is ResizeEdge::ZERO.

Otherwise, an image at width / reduceX by height / reduceY in outFormat:

• if outFormat is single-channel, R contains the distance map.
• if outFormat has alpha, A contains the distance map, while R/G/B contain:
  • if inFormat had R/G/B, the scaled R/G/B of the input image, otherwise
  • 0 in all other channels.

Parameters

inFormat	Any format that is either single-channel, or has an alpha channel.
outFormat	The same requirements as inFormat; channel count does not need to correspond to inFormat.
reduceX	Power-of-two horizontal reduction factor.
reduceY	Power-of-two vertical reduction factor.
srgb	Used in the case of RGBA->RGBA. premultipliedAlpha is omitted.
distanceSpread	Scale factor beyond reduceX and reduceY, of search radius for distance hits.
alphaThreshold	Threshold below which alpha values are considered zero.
flags	Additional behaviors that deviate from VTEX but may be useful; see DistanceFlags.
dither	Internally, distance maps are always computed in floating point. When set to a value other than NONE, and the output format is of integral type, dithering is applied prior to quantization. Depending on the application and contents, this can improve or worsen the quality of the distance map.
filter	Default value mimics VTEX. Does not affect the alpha channel; distance mapping is a distinct sampling operation from source to destination space. Entirely unused if input is single-channel.
edge	Dictates the sampling policy of the distance function regardless of whether there are non-alpha channels to be resized.
valveQuirks	When non-null, mimic VTEX's policy of blanking out any edge pixels in the distance map to 0 (i.e. infinite distance), and report back whether this resulted in any change (such that a command-line tool emulating VTEX would want to report a warning).

Definition at line 474 of file DistanceMapping.cpp.