Package limn.graphics

Enum Class BlendMode

java.lang.Object
java.lang.Enum<BlendMode>
limn.graphics.BlendMode
All Implemented Interfaces:
Serializable, Comparable<BlendMode>, Constable
public enum BlendMode extends Enum<BlendMode>
How subsequent Canvas painting combines with what is already on the target. Part of the canvas state (Canvas.setBlendMode(limn.graphics.BlendMode)), so it is saved/restored with Canvas.save()/Canvas.restore() and applies to every primitive: shapes, text, images.

The pipeline is premultiplied-alpha end to end; each mode maps to a fixed blend equation, and switching modes mid-frame is a batch break (one extra draw call), so group same-mode painting where possible.

Inside a group drawn as one picture, an Opacity container below 1 or a layer, a mode combines with what the group itself drew, and where it drew nothing the source is drawn as itself, as an isolated group of a web page has it; outside any group it combines with the window. A multiplied tint inside a fading container therefore shows as itself while the container fades and multiplies what is beneath once the container is at 1. Inside a group MULTIPLY is drawn in two passes, of which the second reads what the first left, so draws in it share their two draw calls only while no two of them can cover the same pixel, sixty-four at most; each draw that can takes two of its own. What that costs on every frame that draws the group as a picture, while it fades or while it is turned, and never at rest, as measured on a graphics card: shapes a pixel apart or more share (ten rectangles or circles in a row, 3 draw calls; a heat map of 200 cells with one-pixel gaps, 9); shapes that touch or stand less than a pixel apart do not, since beside a corner each one's antialiasing reaches a pixel of the other (ten bars of a chart side by side, 21); ten tints that overlap, about 20 more; a line of text, whose neighbouring glyphs' pictures usually share a pixel, 9 to 11 for 43 characters, where outside a group it is 1.

A 1.x minor release may add constants to this enum: a switch over it needs a default branch.

  • Enum Constant Details

    • NORMAL

      public static final BlendMode NORMAL
      Source-over: ordinary painting, the default.

    • ADDITIVE

      public static final BlendMode ADDITIVE
      Additive: source adds to the destination, for light, glow, fire, laser and particle effects that brighten whatever they overlap. Black is neutral; overlapping strokes accumulate toward white.

    • MULTIPLY

      public static final BlendMode MULTIPLY
      Multiply: source darkens the destination, for shadows, vignettes, tint layers. White is neutral; overlapping strokes accumulate toward black.

  • Method Details

    • values

      public static BlendMode[] values()
      Returns an array containing the constants of this enum class, in the order they are declared.
      Returns:
      an array containing the constants of this enum class, in the order they are declared

    • valueOf

      public static BlendMode valueOf(String name)
      Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)
      Parameters:
      name - the name of the enum constant to be returned.
      Returns:
      the enum constant with the specified name
      Throws:
      IllegalArgumentException - if this enum class has no constant with the specified name
      NullPointerException - if the argument is null