satdump::ChannelTransform Class Reference

Class handling 2D transforms, mainly intended for image channels. This covers a simple but pretty important problem : More...

#include <channel_transform.h>

Public Types
enum	transform_type_t {   TYPE_INVALID = 0 , TYPE_NONE = 1 , TYPE_AFFINE = 2 , TYPE_AFFINE_SLANTX = 3 ,   TYPE_AFFINE_INTERPX = 4 , TYPE_INTERP_XY = 5 }

Public Member Functions
ChannelTransform &	init_none ()
	Initialize a NONE transform.
ChannelTransform &	init_affine (double a_x, double a_y, double b_x, double b_y)
	Initialize an AFFINE transform.
ChannelTransform &	init_affine_slantx (double a_x, double a_y, double b_x, double b_y, double slantx_center, double slantx_ampli)
	Initialize an AFFINE_SLANTX transform.
ChannelTransform &	init_affine_interpx (double a_x, double a_y, double b_x, double b_y, std::vector< std::pair< double, double > > interpx_points)
	Initialize an AFFINE_INTERPX transform.
ChannelTransform &	init_interp_xy (std::vector< std::pair< std::pair< double, double >, std::pair< double, double > > > interp_xy_points)
transform_type_t	getType ()
	Get type of this transform.
void	render ()
	Render ImGui UI to edit the transform.
void	forward (double *x, double *y) const
	Convert channel coordinates to reference coordinates.
void	reverse (double *x, double *y) const
	Convert reference coordinates to channel coordinates.

Friends
void	to_json (nlohmann::json &j, const ChannelTransform &v)
void	from_json (const nlohmann::json &j, ChannelTransform &v)

Detailed Description

Class handling 2D transforms, mainly intended for image channels. This covers a simple but pretty important problem :

Quite often, instrument channels are NOT perfectly aligned... Or the same resolution. This therefore requires the ability to shift them around and re-scale them. However, it often gets more complicated than that. For example, MWS (on AWS) or KMSS are made out of several detectors that are not scanning on the same axis, therefore they also need to be rotated around to align channels.

Instead of pre-aligning them and discarding data, or handling those cases specifically, this class defines several common or arbitrary transforms to convert each channel to a "reference" field. Therefore, by taking a channel's 2D X/Y coordinates, running it through its own reference's forward and then the target channel's reverse will give the equivalent coordinates on the other channel.

Available transforms are :

• 0, Invalid : Default, throws an exception
• 1, None : Does nothing, use if no transform is required between channels
• 2, Affine : ax + b form applied on both axis, meant for simple translations and resolution changes
• 3, Affine Slant X : Combines the affine transform and a shift in y identical at any point in x
• 4, Affine + Arbtitrary interpolation on the X axis (eg, for VIIRS with discountinuties between channels)
• 5, TODOREWORK

Member Function Documentation

forward()

void satdump::ChannelTransform::forward ( double * x, double * y ) const

inline

Convert channel coordinates to reference coordinates.

Parameters

x	coordinate to be transformed
y	coordinate to be transformed

getType()

ChannelTransform::transform_type_t satdump::ChannelTransform::getType

(

)

Get type of this transform.

Returns

type of the transform

init_affine()

ChannelTransform & satdump::ChannelTransform::init_affine	(	double	a_x,
		double	a_y,
		double	b_x,
		double	b_y )

Initialize an AFFINE transform.

Parameters

a_x	affine a for x axis
a_y	affine a for y axis
b_x	affine b for x axis
b_y	affine b for y axis

init_affine_interpx()

ChannelTransform & satdump::ChannelTransform::init_affine_interpx	(	double	a_x,
		double	a_y,
		double	b_x,
		double	b_y,
		std::vector< std::pair< double, double > >	interpx_points )

Initialize an AFFINE_INTERPX transform.

Parameters

a_x	affine a for x axis
a_y	affine a for y axis
b_x	affine b for x axis
b_y	affine b for y axis
interpx_points	points for x axis interpolation

init_affine_slantx()

ChannelTransform & satdump::ChannelTransform::init_affine_slantx	(	double	a_x,
		double	a_y,
		double	b_x,
		double	b_y,
		double	slantx_center,
		double	slantx_ampli )

Initialize an AFFINE_SLANTX transform.

Parameters

a_x	affine a for x axis
a_y	affine a for y axis
b_x	affine b for x axis
b_y	affine b for y axis
slantx_center	center of the slant on the x axis
slantx_ampli	multiplicator applied after substracting center

init_none()

ChannelTransform & satdump::ChannelTransform::init_none

(

)

Initialize a NONE transform.

Parameters

render()

void satdump::ChannelTransform::render

(

)

Render ImGui UI to edit the transform.

Parameters

reverse()

void satdump::ChannelTransform::reverse ( double * x, double * y ) const

inline

Convert reference coordinates to channel coordinates.

Parameters

x	coordinate to be transformed
y	coordinate to be transformed

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

• src-core/products/image/channel_transform.h
• src-core/products/image/channel_transform.cpp
• src-core/products/image/channel_transform_render.cpp