Table of Contents

Class AbstractLinearGradientBuilder

Namespace
iText.Kernel.Colors.Gradients
Assembly
itext.kernel.dll

Base class for linear gradient builders implementations.

public abstract class AbstractLinearGradientBuilder
Inheritance
AbstractLinearGradientBuilder
Derived
Inherited Members

Remarks

Base class for linear gradient builders implementations.

Color transitions for linear gradients are defined by a series of color stops along a gradient vector. A gradient normal defines how the colors in a vector are painted to the surface. For a linear gradient, a normal is a line perpendicular to the vector.

Contains the main logic that works with stop colors and creation of the resulted pdf color object.

Constructors

AbstractLinearGradientBuilder() 

protected AbstractLinearGradientBuilder()

Fields

ZERO_EPSILON

The epsilon value used for data creation

protected const double ZERO_EPSILON = 1E-10

Field Value

double

Methods

AddColorStop(GradientColorStop)

Adds the new color stop to the end ( more info ).

public virtual AbstractLinearGradientBuilder AddColorStop(GradientColorStop gradientColorStop)

Parameters

gradientColorStop GradientColorStop

the gradient stop color to add

Returns

AbstractLinearGradientBuilder

the current builder instance

Remarks

Adds the new color stop to the end ( more info ). Note: if the previously added color stop's offset would have grater offset than the added one, then the new offset would be normalized to be equal to the previous one. (Comparison made between relative on coordinates vector offsets. If any of them has the absolute offset, then the absolute value would converted to relative first.)

BuildColor(Rectangle, AffineTransform, PdfDocument)

Builds the Color object representing the linear gradient with specified configuration that fills the target bounding box.

public virtual Color BuildColor(Rectangle targetBoundingBox, AffineTransform contextTransform, PdfDocument document)

Parameters

targetBoundingBox Rectangle

the bounding box to be filled in current space

contextTransform AffineTransform

the transformation from the base coordinates space into the current space. The null value is valid and can be used if there is no transformation from base coordinates to current space specified, or it is equal to identity transformation.

document PdfDocument

the PdfDocument for which the linear gradient would be built.

Returns

Color

the constructed Color or null if no color to be applied or base gradient vector has been specified

CreateCoordinatesForNewDomain(double[], Point[])

Expand the base vector to cover the new domain

protected static Point[] CreateCoordinatesForNewDomain(double[] newDomain, Point[] baseVector)

Parameters

newDomain double[]

the array of exactly two elements that specifies the domain that should be covered by the created vector

baseVector Point[]

the array of exactly two elements that specifies the base vector which corresponds to [0, 1] domain

Returns

Point[]

the array of two

EvaluateCoveringDomain(Point[], Rectangle)

Evaluates the minimal domain that covers the box with vector normals.

protected static double[] EvaluateCoveringDomain(Point[] coords, Rectangle toCover)

Parameters

coords Point[]

the array of exactly two elements that describe the base vector (corresponding to [0,1] domain, that need to be adjusted to cover the box

toCover Rectangle

the box that needs to be covered

Returns

double[]

the array of two elements in ascending order specifying the calculated covering domain

Remarks

Evaluates the minimal domain that covers the box with vector normals. The domain corresponding to the initial vector is [0, 1].

GetColorStops()

Get the copy of current color stops list.

public virtual IList<GradientColorStop> GetColorStops()

Returns

IList<GradientColorStop>

the copy of current stop colors list

Remarks

Get the copy of current color stops list. Note that the stop colors are not copied here

GetCurrentSpaceToGradientVectorSpaceTransformation(Rectangle, AffineTransform)

Returns the current space to gradient vector space transformations that should be applied to the shading color.

protected virtual AffineTransform GetCurrentSpaceToGradientVectorSpaceTransformation(Rectangle targetBoundingBox, AffineTransform contextTransform)

Parameters

targetBoundingBox Rectangle

the rectangle to be covered by constructed color in current space

contextTransform AffineTransform

the current canvas transformation

Returns

AffineTransform

the additional transformation to be concatenated to the current for resulted shading or null if no additional transformation is specified

Remarks

Returns the current space to gradient vector space transformations that should be applied to the shading color. The transformation should be invertible as the current target bounding box coordinates should be transformed into the resulted shading space coordinates.

GetGradientVector(Rectangle, AffineTransform)

Returns the base gradient vector in gradient vector space.

protected abstract Point[] GetGradientVector(Rectangle targetBoundingBox, AffineTransform contextTransform)

Parameters

targetBoundingBox Rectangle

the rectangle to be covered by constructed color in current space

contextTransform AffineTransform

the current canvas transformation

Returns

Point[]

the array of exactly two elements specifying the gradient coordinates vector

Remarks

Returns the base gradient vector in gradient vector space. This vector would be set as shading coordinates vector and its length would be used to translate all color stops absolute offsets into the relatives.

GetSpreadMethod()

Get the current spread method

public virtual GradientSpreadMethod GetSpreadMethod()

Returns

GradientSpreadMethod

the current spread method

SetSpreadMethod(GradientSpreadMethod)

Set the spread method to use for the gradient

public virtual AbstractLinearGradientBuilder SetSpreadMethod(GradientSpreadMethod gradientSpreadMethod)

Parameters

gradientSpreadMethod GradientSpreadMethod

the gradient spread method to set

Returns

AbstractLinearGradientBuilder

the current builder instance