com.itextpdf.kernel.colors.gradients

Class AbstractLinearGradientBuilder

java.lang.Object

com.itextpdf.kernel.colors.gradients.AbstractLinearGradientBuilder

Direct Known Subclasses:

LinearGradientBuilder, StrategyBasedLinearGradientBuilder

public abstract class AbstractLinearGradientBuilder
extends Object

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.

Field Summary

Fields

Modifier and Type	Field and Description
protected static double	ZERO_EPSILON The epsilon value used for data creation

Constructor Summary

Constructors

Constructor and Description
AbstractLinearGradientBuilder()

Method Summary

Modifier and Type	Method and Description
AbstractLinearGradientBuilder	addColorStop(GradientColorStop gradientColorStop) Adds the new color stop to the end (more info).
Color	buildColor(Rectangle targetBoundingBox, AffineTransform contextTransform, PdfDocument document) Builds the Color object representing the linear gradient with specified configuration that fills the target bounding box.
protected static Point[]	createCoordinatesForNewDomain(double[] newDomain, Point[] baseVector) Expand the base vector to cover the new domain
protected static double[]	evaluateCoveringDomain(Point[] coords, Rectangle toCover) Evaluates the minimal domain that covers the box with vector normals.
List<GradientColorStop>	getColorStops() Get the copy of current color stops list.
protected AffineTransform	getCurrentSpaceToGradientVectorSpaceTransformation(Rectangle targetBoundingBox, AffineTransform contextTransform) Returns the current space to gradient vector space transformations that should be applied to the shading color.
protected abstract Point[]	getGradientVector(Rectangle targetBoundingBox, AffineTransform contextTransform) Returns the base gradient vector in gradient vector space.
GradientSpreadMethod	getSpreadMethod() Get the current spread method
AbstractLinearGradientBuilder	setSpreadMethod(GradientSpreadMethod gradientSpreadMethod) Set the spread method to use for the gradient

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ZERO_EPSILON

protected static final double ZERO_EPSILON

The epsilon value used for data creation

See Also:

Constant Field Values

Constructor Detail

AbstractLinearGradientBuilder

public AbstractLinearGradientBuilder()

Method Detail

addColorStop

public AbstractLinearGradientBuilder addColorStop(GradientColorStop gradientColorStop)

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.)

Parameters:

gradientColorStop - the gradient stop color to add

Returns:

the current builder instance

setSpreadMethod

public AbstractLinearGradientBuilder setSpreadMethod(GradientSpreadMethod gradientSpreadMethod)

Set the spread method to use for the gradient

Parameters:

gradientSpreadMethod - the gradient spread method to set

Returns:

the current builder instance

getColorStops

public List<GradientColorStop> getColorStops()

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

Returns:

the copy of current stop colors list

getSpreadMethod

public GradientSpreadMethod getSpreadMethod()

Get the current spread method

Returns:

the current spread method

buildColor

public Color buildColor(Rectangle targetBoundingBox,
                        AffineTransform contextTransform,
                        PdfDocument document)

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

Parameters:

targetBoundingBox - the bounding box to be filled in current space

contextTransform - 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 - the PdfDocument for which the linear gradient would be built.

Returns:

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

getGradientVector

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

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.

Parameters:

targetBoundingBox - the rectangle to be covered by constructed color in current space

contextTransform - the current canvas transformation

Returns:

the array of exactly two elements specifying the gradient coordinates vector

getCurrentSpaceToGradientVectorSpaceTransformation

protected AffineTransform getCurrentSpaceToGradientVectorSpaceTransformation(Rectangle targetBoundingBox,
                                                                             AffineTransform contextTransform)

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.

Parameters:

targetBoundingBox - the rectangle to be covered by constructed color in current space

contextTransform - the current canvas transformation

Returns:

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

evaluateCoveringDomain

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

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

Parameters:

coords - 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 - the box that needs to be covered

Returns:

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

createCoordinatesForNewDomain

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

Expand the base vector to cover the new domain

Parameters:

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

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

Returns:

the array of two