PixelSampleMapper Class Reference

Utility class to calculate sample range for a given column. More...

#include <PixelSampleMapper.h>

Classes
struct	LinearMapper

Public Types
using	CustomMapper = std::function< sampleCount(uint32_t)>

Public Member Functions
	PixelSampleMapper ()=default
	PixelSampleMapper (const PixelSampleMapper &)=default
	PixelSampleMapper (PixelSampleMapper &&)=default
PixelSampleMapper &	operator= (const PixelSampleMapper &)=default
PixelSampleMapper &	operator= (PixelSampleMapper &&)=default
	PixelSampleMapper (double t0, double rate, double samplesPerPixel) noexcept
void	applyBias (double bias) noexcept
double	applyCorrection (const PixelSampleMapper &oldMapper, size_t oldLen, size_t newLen)
sampleCount	GetFirstSample (uint32_t column) const
sampleCount	GetLastSample (uint32_t column) const
std::pair< sampleCount, sampleCount >	GetSampleRange (uint32_t column) const
void	setCustomMapper (CustomMapper mapper)
bool	IsValid () const
bool	IsLinear () const noexcept

Private Attributes
std::variant< LinearMapper, CustomMapper >	mMapper { LinearMapper {} }

Detailed Description

Utility class to calculate sample range for a given column.

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Audacity: A Digital Audio Editor

PixelSampleMapper.h

Dmitry Vedenko

Definition at line 22 of file PixelSampleMapper.h.

Member Typedef Documentation

CustomMapper

using PixelSampleMapper::CustomMapper = std::function<sampleCount(uint32_t)>

Definition at line 42 of file PixelSampleMapper.h.

Constructor & Destructor Documentation

PixelSampleMapper() [1/4]

PixelSampleMapper::PixelSampleMapper ( )

default

PixelSampleMapper() [2/4]

PixelSampleMapper::PixelSampleMapper ( const PixelSampleMapper &  )

default

PixelSampleMapper() [3/4]

PixelSampleMapper::PixelSampleMapper ( PixelSampleMapper &&  )

default

PixelSampleMapper() [4/4]

PixelSampleMapper::PixelSampleMapper ( double  t0, double  rate, double  samplesPerPixel  )

noexcept

---

Audacity: A Digital Audio Editor

PixelSampleMapper.h

Dmitry Vedenko

Definition at line 19 of file PixelSampleMapper.cpp.

    : mMapper(LinearMapper { (0.5 + t0 * rate), samplesPerPixel })
{
   assert((0.5 + t0 * rate) >= 0.0);
}

Member Function Documentation

applyBias()

void PixelSampleMapper::applyBias ( double  bias )

noexcept

Definition at line 26 of file PixelSampleMapper.cpp.

{
   auto mapper = std::get_if<LinearMapper>(&mMapper);
 
   if (mapper != nullptr)
      mapper->mInitialValue += bias;
}

applyCorrection()

double PixelSampleMapper::applyCorrection	(	const PixelSampleMapper &	oldMapper,
		size_t	oldLen,
		size_t	newLen
	)

Definition at line 34 of file PixelSampleMapper.cpp.

{
   assert(mMapper.index() == 0);
   assert(oldMapper.mMapper.index() == 0);
 
   LinearMapper* currentMapper = std::get_if<LinearMapper>(&mMapper);
 
   if (currentMapper == nullptr)
      return {};
 
   const LinearMapper* oldLinearMapper =
      std::get_if<LinearMapper>(&oldMapper.mMapper);
 
   if (oldLinearMapper == nullptr)
      return {};
 
   // Find the sample position that is the origin in the old cache.
   const double oldWhere0 =
      (*oldLinearMapper)(1).as_double() - currentMapper->mSamplesPerPixel;
   const double oldWhereLast =
      oldWhere0 + oldLen * currentMapper->mSamplesPerPixel;
   // Find the length in samples of the old cache.
   const double denom = oldWhereLast - oldWhere0;
 
   // What sample would go in where[0] with no correction?
   const double guessWhere0 =
      currentMapper->mInitialValue - 0.5; // Why do we ignore initial bias?
 
   if ( // Skip if old and NEW are disjoint:
      oldWhereLast <= guessWhere0 ||
      guessWhere0 + newLen * currentMapper->mSamplesPerPixel <= oldWhere0 ||
      // Skip unless denom rounds off to at least 1.
      denom < 0.5)
   {
      // The computation of oldX0 in the other branch
      // may underflow and the assertion would be violated.
      return oldLen;
   }
   else
   {
      // What integer position in the old cache array does that map to?
      // (even if it is out of bounds)
      const auto oldX0 =
         std::floor(0.5 + oldLen * (guessWhere0 - oldWhere0) / denom);
      // What sample count would the old cache have put there?
      const double where0 =
         oldWhere0 + double(oldX0) * currentMapper->mSamplesPerPixel;
      // What correction is needed to align the NEW cache with the old?
      const double correction0 = where0 - guessWhere0;
      const double correction = std::max(
         -currentMapper->mSamplesPerPixel,
         std::min(currentMapper->mSamplesPerPixel, correction0));
 
      assert(correction == correction0);
 
      currentMapper->mInitialValue += correction;
 
      return oldX0;
   }
}

References min(), PixelSampleMapper::LinearMapper::mInitialValue, mMapper, and PixelSampleMapper::LinearMapper::mSamplesPerPixel.

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GetFirstSample()

sampleCount PixelSampleMapper::GetFirstSample

(

uint32_t

column

)

const

Definition at line 96 of file PixelSampleMapper.cpp.

{
   return Variant::Visit(
      [column](const auto& mapper) { return mapper(column); }, mMapper);
}

References mMapper, and Variant::Visit().

Referenced by GetLastSample(), and GetSampleRange().

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GetLastSample()

sampleCount PixelSampleMapper::GetLastSample

(

uint32_t

column

)

const

Definition at line 102 of file PixelSampleMapper.cpp.

{
   return GetFirstSample(column + 1);
}

References GetFirstSample().

Referenced by GetSampleRange().

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GetSampleRange()

std::pair< sampleCount, sampleCount > PixelSampleMapper::GetSampleRange

(

uint32_t

column

)

const

Definition at line 108 of file PixelSampleMapper.cpp.

{
   return { GetFirstSample(column), GetLastSample(column) };
}

References GetFirstSample(), and GetLastSample().

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IsLinear()

bool PixelSampleMapper::IsLinear ( ) const

noexcept

Definition at line 123 of file PixelSampleMapper.cpp.

{
   return std::get_if<LinearMapper>(&mMapper) != nullptr;
}

References mMapper.

IsValid()

bool PixelSampleMapper::IsValid

(

)

const

Definition at line 118 of file PixelSampleMapper.cpp.

{
   return Variant::Visit([](const auto& mapper) { return !!mapper; }, mMapper);
}

References mMapper, and Variant::Visit().

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operator=() [1/2]

PixelSampleMapper & PixelSampleMapper::operator= ( const PixelSampleMapper &  )

default

operator=() [2/2]

PixelSampleMapper & PixelSampleMapper::operator= ( PixelSampleMapper &&  )

default

setCustomMapper()

void PixelSampleMapper::setCustomMapper

(

CustomMapper

mapper

)

Definition at line 113 of file PixelSampleMapper.cpp.

{
   mMapper = std::move(mapper);
}

References mMapper.

Member Data Documentation

mMapper

std::variant<LinearMapper, CustomMapper> PixelSampleMapper::mMapper { LinearMapper {} }

private

Definition at line 69 of file PixelSampleMapper.h.

Referenced by applyCorrection(), GetFirstSample(), IsLinear(), IsValid(), and setCustomMapper().

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

• PixelSampleMapper.h
• PixelSampleMapper.cpp