Package 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 Details

    • ZERO_EPSILON

      protected static final double ZERO_EPSILON
      The epsilon value used for data creation
      See Also:

  • Constructor Details

    • AbstractLinearGradientBuilder

      public AbstractLinearGradientBuilder()

  • Method Details

    • 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