#include <SkGainmapInfo.h>

Public Types
enum class	BaseImageType { kSDR , kHDR }

enum class	Type { kDefault }

Public Member Functions
bool	operator== (const SkGainmapInfo &other) const

bool	operator!= (const SkGainmapInfo &other) const

Public Attributes
SkColor4f	fGainmapRatioMin = {1.f, 1.f, 1.f, 1.0}

SkColor4f	fGainmapRatioMax = {2.f, 2.f, 2.f, 1.0}

SkColor4f	fGainmapGamma = {1.f, 1.f, 1.f, 1.f}

SkColor4f	fEpsilonSdr = {0.f, 0.f, 0.f, 1.0}

SkColor4f	fEpsilonHdr = {0.f, 0.f, 0.f, 1.0}

float	fDisplayRatioSdr = 1.f

float	fDisplayRatioHdr = 2.f

BaseImageType	fBaseImageType = BaseImageType::kSDR

sk_sp< SkColorSpace >	fGainmapMathColorSpace = nullptr

Type	fType = Type::kDefault

Detailed Description

Gainmap rendering parameters. Suppose our display has HDR to SDR ratio of H and we wish to display an image with gainmap on this display. Let B be the pixel value from the base image in a color space that has the primaries of the base image and a linear transfer function. Let G be the pixel value from the gainmap. Let D be the output pixel in the same color space as B. The value of D is computed as follows:

First, let W be a weight parameter determing how much the gainmap will be applied. W = clamp((log(H) - log(fDisplayRatioSdr)) / (log(fDisplayRatioHdr) - log(fDisplayRatioSdr), 0, 1)

Next, let L be the gainmap value in log space. We compute this from the value G that was sampled from the texture as follows: L = mix(log(fGainmapRatioMin), log(fGainmapRatioMax), pow(G, fGainmapGamma))

Finally, apply the gainmap to compute D, the displayed pixel. If the base image is SDR then compute: D = (B + fEpsilonSdr) * exp(L * W) - fEpsilonHdr If the base image is HDR then compute: D = (B + fEpsilonHdr) * exp(L * (W - 1)) - fEpsilonSdr

In the above math, log() is a natural logarithm and exp() is natural exponentiation. Note, however, that the base used for the log() and exp() functions does not affect the results of the computation (it cancels out, as long as the same base is used throughout).

This product includes Gain Map technology under license by Adobe.

Definition at line 41 of file SkGainmapInfo.h.

Member Enumeration Documentation

◆ BaseImageType

enum class SkGainmapInfo::BaseImageType

strong

Whether the base image is the SDR image or the HDR image.

Enumerator
kSDR
kHDR

Definition at line 69 of file SkGainmapInfo.h.

◆ Type

enum class SkGainmapInfo::Type

strong

Enumerator
kDefault

Definition at line 94 of file SkGainmapInfo.h.

                    {
        kDefault,
    };

Member Function Documentation

◆ operator!=()

bool SkGainmapInfo::operator!= ( const SkGainmapInfo & other ) const

inline

Definition at line 91 of file SkGainmapInfo.h.

91{ return !(*this == other); }

◆ operator==()

bool SkGainmapInfo::operator== ( const SkGainmapInfo & other ) const

inline

Definition at line 81 of file SkGainmapInfo.h.

                                                             {
        return fGainmapRatioMin == other.fGainmapRatioMin &&
               fGainmapRatioMax == other.fGainmapRatioMax && fGainmapGamma == other.fGainmapGamma &&
               fEpsilonSdr == other.fEpsilonSdr && fEpsilonHdr == other.fEpsilonHdr &&
               fDisplayRatioSdr == other.fDisplayRatioSdr &&
               fDisplayRatioHdr == other.fDisplayRatioHdr &&
               fBaseImageType == other.fBaseImageType &&
               SkColorSpace::Equals(fGainmapMathColorSpace.get(),
                                    other.fGainmapMathColorSpace.get());
    }

Member Data Documentation

◆ fBaseImageType

BaseImageType SkGainmapInfo::fBaseImageType = BaseImageType::kSDR

Definition at line 73 of file SkGainmapInfo.h.

◆ fDisplayRatioHdr

float SkGainmapInfo::fDisplayRatioHdr = 2.f

Definition at line 64 of file SkGainmapInfo.h.

◆ fDisplayRatioSdr

float SkGainmapInfo::fDisplayRatioSdr = 1.f

If the output display's HDR to SDR ratio is less or equal than fDisplayRatioSdr then the SDR rendition is displayed. If the output display's HDR to SDR ratio is greater or equal than fDisplayRatioHdr then the HDR rendition is displayed. If the output display's HDR to SDR ratio is between these values then an interpolation between the two is displayed using the math above.

Definition at line 63 of file SkGainmapInfo.h.

◆ fEpsilonHdr

SkColor4f SkGainmapInfo::fEpsilonHdr = {0.f, 0.f, 0.f, 1.0}

Definition at line 54 of file SkGainmapInfo.h.

54{0.f, 0.f, 0.f, 1.0};

◆ fEpsilonSdr

SkColor4f SkGainmapInfo::fEpsilonSdr = {0.f, 0.f, 0.f, 1.0}

Parameters sometimes used in gainmap computation to avoid numerical instability.

Definition at line 53 of file SkGainmapInfo.h.

53{0.f, 0.f, 0.f, 1.0};

◆ fGainmapGamma

SkColor4f SkGainmapInfo::fGainmapGamma = {1.f, 1.f, 1.f, 1.f}

Definition at line 48 of file SkGainmapInfo.h.

48{1.f, 1.f, 1.f, 1.f};

◆ fGainmapMathColorSpace

sk_sp<SkColorSpace> SkGainmapInfo::fGainmapMathColorSpace = nullptr

If specified, color space to apply the gainmap in, otherwise the base image's color space is used. Only the color primaries are used, the transfer function is irrelevant.

Definition at line 79 of file SkGainmapInfo.h.

◆ fGainmapRatioMax

SkColor4f SkGainmapInfo::fGainmapRatioMax = {2.f, 2.f, 2.f, 1.0}

Definition at line 47 of file SkGainmapInfo.h.

47{2.f, 2.f, 2.f, 1.0};

◆ fGainmapRatioMin

SkColor4f SkGainmapInfo::fGainmapRatioMin = {1.f, 1.f, 1.f, 1.0}

Parameters for converting the gainmap from its image encoding to log space. These are specified per color channel. The alpha value is unused.

Definition at line 46 of file SkGainmapInfo.h.

46{1.f, 1.f, 1.f, 1.0};

◆ fType

Type SkGainmapInfo::fType = Type::kDefault

Definition at line 97 of file SkGainmapInfo.h.

The documentation for this struct was generated from the following file:

third_party/skia/include/private/SkGainmapInfo.h

Public Types

Public Member Functions

Public Attributes