pdftron::PDF::Shading Class Reference

Shading is a class that represents a flat interface around all PDF shading types:. More...

#include <Shading.h>

List of all members.

Public Types
enum	Type {   e_function_shading, e_axial_shading, e_radial_shading, e_free_gouraud_shading,   e_lattice_gouraud_shading, e_coons_shading, e_tensor_shading, e_null }
Public Member Functions
	Shading (SDF::Obj shading_dict=0)
	Create a Shading from the given SDF/Cos object listed under /Shading entry in the page Resource dictionary.
	Shading (const Shading &s)
Shading &	operator= (const Shading &s)
	~Shading ()
Shading::Type	GetType () const
	Returns: The shading type
SDF::Obj	GetSDFObj ()
	Returns: the underlying SDF/Cos object
ColorSpace	GetBaseColorSpace ()
	Returns: The color space in which color values are expressed.
bool	HasBBox ()
	Returns: true if shading has a bounding box, false otherwise.
Rect	GetBBox ()
	Returns: a rectangle giving the left, bottom, right, and top coordinates, respectively, of the shading’s bounding box.
bool	HasBackground ()
	Returns: true if the shading has a background color or false otherwise.
ColorPt	GetBackground ()
	An color point represented in base color space specifying a single background color value.
bool	GetAntialias ()
	Returns: A flag indicating whether to filter the shading function to prevent aliasing artifacts.
double	GetParamStart ()
	Returns: a number specifying the limiting value of a parametric variable t.
double	GetParamEnd ()
	Returns: a number specifying the limiting value of a parametric variable t.
bool	IsExtendStart ()
	Returns: a flag specifying whether to extend the shading beyond the starting point of the axis for Axial shading or starting circle for Radial shading.
bool	IsExtendEnd ()
	Returns: a flag specifying whether to extend the shading beyond the ending point of the axis for Axial shading or ending circle for Radial shading.
void	GetColor (double t, ColorPt &out_color)
	Returns: a color point for the given value of parametric variable t.
void	GetCoords (double &out_x0, double &out_y0, double &out_x1, double &out_y1)
	Returns: for Axial shading returns four numbers (out_x0, out_y0, out_x1, out_y1) specifying the starting and ending coordinates of the axis, expressed in the shading’s target coordinate space.
void	GetCoords (double &out_x0, double &out_y0, double &out_r0, double &out_x1, double &out_y1, double &out_r1)
	Returns: for Radial shading returns six numbers (x0 y0 r0 x1 y1 r1) specifying the centers and radii of the starting and ending circles, expressed in the shading’s target coordinate space.
void	GetDomain (double &out_xmin, double &out_xmax, double &out_ymin, double &out_ymax)
	Returns: An array of four numbers [xmin xmax ymin ymax] specifying the rectangular domain of coordinates over which the color function(s) are defined.
Common::Matrix2D	GetMatrix ()
	Returns: a matrix specifying a mapping from the coordinate space specified by the Domain entry into the shading’s target coordinate space.
void	GetColor (double t1, double t2, ColorPt &out_color)
	Returns: a color point for the given value of parametric variable (t1, t2).
Static Public Member Functions
static Type	GetType (SDF::Obj shading_dict)
	Returns: The Type of a given SDF/Cos shading dictionary, or e_null for if SDF object is not a valid shading object

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Detailed Description

Shading is a class that represents a flat interface around all PDF shading types:.

• In Function-based (type 1) shadings, the color at every point in the domain is defined by a specified mathematical function. The function need not be smooth or continuous. This is the most general of the available shading types, and is useful for shadings that cannot be adequately described with any of the other types.

• Axial shadings (type 2) define a color blend along a line between two points, optionally extended beyond the boundary points by continuing the boundary colors.

• Radial shadings (type 3) define a color blend that varies between two circles. Shadings of this type are commonly used to depict three-dimensional spheres and cones.

• Free-form Gouraud-shaded triangle mesh shadings (type 4) and lattice gouraud shadings (type 5) are commonly used to represent complex colored and shaded three-dimensional shapes. The area to be shaded is defined by a path composed entirely of triangles. The color at each vertex of the triangles is specified, and a technique known as Gouraud interpolation is used to color the interiors. The interpolation functions defining the shading may be linear or nonlinear.

• Coons patch mesh shadings (type 6) are constructed from one or more color patches, each bounded by four cubic Bézier curves.

A Coons patch generally has two independent aspects:

• Colors are specified for each corner of the unit square, and bilinear interpolation is used to fill in colors over the entire unit square
  
• Coordinates are mapped from the unit square into a four-sided patch whose sides are not necessarily linear. The mapping is continuous: the corners of the unit square map to corners of the patch and the sides of the unit square map to sides of the patch.

• Tensor-product patch mesh shadings (type 7) are identical to type 6 (Coons mesh), except that they are based on a bicubic tensor-product patch defined by 16 control points, instead of the 12 control points that define a Coons patch. The shading Patterns dictionaries representing the two patch types differ only in the value of the Type entry and in the number of control points specified for each patch in the data stream. Although the Coons patch is more concise and easier to use, the tensor- product patch affords greater control over color mapping.

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Member Enumeration Documentation

enum pdftron::PDF::Shading::Type

Enumerator:

e_function_shading
e_axial_shading
e_radial_shading
e_free_gouraud_shading
e_lattice_gouraud_shading
e_coons_shading
e_tensor_shading
e_null

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Constructor & Destructor Documentation

pdftron::PDF::Shading::Shading

(

SDF::Obj

shading_dict = 0

)

Create a Shading from the given SDF/Cos object listed under /Shading entry in the page Resource dictionary.

If shading_dict dictionary is null, a non valid Shading object is created.

pdftron::PDF::Shading::Shading

(

const Shading &

s

)

pdftron::PDF::Shading::~Shading

(

)

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Member Function Documentation

Shading& pdftron::PDF::Shading::operator=

(

const Shading &

s

)

static Type pdftron::PDF::Shading::GetType

(

SDF::Obj

shading_dict

)

[static]

Returns:

The Type of a given SDF/Cos shading dictionary, or e_null for if SDF object is not a valid shading object

Parameters:

cs

Shading::Type pdftron::PDF::Shading::GetType

(

)

const

Returns:

The shading type

SDF::Obj pdftron::PDF::Shading::GetSDFObj

(

)

Returns:

the underlying SDF/Cos object

ColorSpace pdftron::PDF::Shading::GetBaseColorSpace

(

)

Returns:

The color space in which color values are expressed.

This may be any device, CIE-based, or special color space except a Pattern space.

bool pdftron::PDF::Shading::HasBBox

(

)

Returns:

true if shading has a bounding box, false otherwise.

Rect pdftron::PDF::Shading::GetBBox

(

)

Returns:

a rectangle giving the left, bottom, right, and top coordinates, respectively, of the shading’s bounding box.

The coordinates are interpreted in the shading’s target coordinate space. If present, this bounding box is applied as a temporary clipping boundary when the shading is painted, in addition to the current clipping path and any other clipping boundaries in effect at that time.

Note:

Use HasBBox() method to determine whether the shading has a background color.

bool pdftron::PDF::Shading::HasBackground

(

)

Returns:

true if the shading has a background color or false otherwise.

ColorPt pdftron::PDF::Shading::GetBackground

(

)

An color point represented in base color space specifying a single background color value.

If present, this color is used before any painting operation involving the shading, to fill those portions of the area to be painted that lie outside the bounds of the shading object itself. In the opaque imaging model, the effect is as if the painting operation were performed twice: first with the background color and then again with the shading.

Note:

The background color is applied only when the shading is used as part of a shading pattern, not when it is painted directly with the sh operator.

Use HasBackground() method to determine whether the shading has a background color.

bool pdftron::PDF::Shading::GetAntialias

(

)

Returns:

A flag indicating whether to filter the shading function to prevent aliasing artifacts.

See Table 4.25

double pdftron::PDF::Shading::GetParamStart

(

)

Returns:

a number specifying the limiting value of a parametric variable t.

The variable is considered to vary linearly between GetParamStart() and GetParamEnd() as the color gradient varies between the starting and ending points of the axis for Axial shading or circles for Radial shading. The variable t becomes the input argument to the color function(s).

Note:

the returned value corresponds to the first value in Domain array.

for shadings other than Axial or Radial this method throws an exception.

double pdftron::PDF::Shading::GetParamEnd

(

)

Returns:

a number specifying the limiting value of a parametric variable t.

The variable is considered to vary linearly between GetParamStart() and GetParamEnd() as the color gradient varies between the starting and ending points of the axis for Axial shading or circles for Radial shading. The variable t becomes the input argument to the color function(s).

Note:

the returned value corresponds to the second value in Domain array.

for shadings other than Axial or Radial this method throws an exception.

bool pdftron::PDF::Shading::IsExtendStart

(

)

Returns:

a flag specifying whether to extend the shading beyond the starting point of the axis for Axial shading or starting circle for Radial shading.

Note:

for shadings other than Axial or Radial this method throws an exception.

bool pdftron::PDF::Shading::IsExtendEnd

(

)

Returns:

a flag specifying whether to extend the shading beyond the ending point of the axis for Axial shading or ending circle for Radial shading.

Note:

for shadings other than Axial or Radial this method throws an exception.

void pdftron::PDF::Shading::GetColor	(	double	t,
		ColorPt &	out_color
	)

Returns:

a color point for the given value of parametric variable t.

Note:

for shadings other than Axial or Radial this method throws an exception.

void pdftron::PDF::Shading::GetCoords	(	double &	out_x0,
		double &	out_y0,
		double &	out_x1,
		double &	out_y1
	)

Returns:

for Axial shading returns four numbers (out_x0, out_y0, out_x1, out_y1) specifying the starting and ending coordinates of the axis, expressed in the shading’s target coordinate space.

Note:

for shadings other than Axial this method throws an exception.

void pdftron::PDF::Shading::GetCoords	(	double &	out_x0,
		double &	out_y0,
		double &	out_r0,
		double &	out_x1,
		double &	out_y1,
		double &	out_r1
	)

Returns:

for Radial shading returns six numbers (x0 y0 r0 x1 y1 r1) specifying the centers and radii of the starting and ending circles, expressed in the shading’s target coordinate space.

The radii r0 and r1 must both be greater than or equal to 0. If one radius is 0, the corresponding circle is treated as a point; if both are 0, nothing is painted.

Note:

for shadings other than Radial this method throws an exception.

void pdftron::PDF::Shading::GetDomain	(	double &	out_xmin,
		double &	out_xmax,
		double &	out_ymin,
		double &	out_ymax
	)

Returns:

An array of four numbers [xmin xmax ymin ymax] specifying the rectangular domain of coordinates over which the color function(s) are defined.

If the function does not contain /Domain entry the function returns: [0 1 0 1].

Note:

for shadings other than Function this method throws an exception.

Common::Matrix2D pdftron::PDF::Shading::GetMatrix

(

)

Returns:

a matrix specifying a mapping from the coordinate space specified by the Domain entry into the shading’s target coordinate space.

Note:

for shadings other than Function this method throws an exception.

void pdftron::PDF::Shading::GetColor	(	double	t1,
		double	t2,
		ColorPt &	out_color
	)

Returns:

a color point for the given value of parametric variable (t1, t2).

Note:

for shadings other than Function this method throws an exception.

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