R: Define Gradient and Pattern Fills

patterns {grid}

R Documentation

Define Gradient and Pattern Fills

Description

Functions to define gradient fills and pattern fills.

Usage

linearGradient(colours = c("black", "white"),
               stops = seq(0, 1, length.out = length(colours)),
               x1 = unit(0, "npc"), y1 = unit(0, "npc"),  
               x2 = unit(1, "npc"), y2 = unit(1, "npc"),
               default.units = "npc",
               extend = c("pad", "repeat", "reflect", "none"),
               group = TRUE) 
radialGradient(colours = c("black", "white"),
               stops = seq(0, 1, length.out = length(colours)),
               cx1 = unit(.5, "npc"), cy1 = unit(.5, "npc"),
               r1 = unit(0, "npc"),
               cx2 = unit(.5, "npc"), cy2 = unit(.5, "npc"),
               r2 = unit(.5, "npc"),
               default.units = "npc",
               extend = c("pad", "repeat", "reflect", "none"),
               group = TRUE) 
pattern(grob,
        x = 0.5, y = 0.5, width = 1, height = 1,
        default.units = "npc",
        just="centre", hjust=NULL, vjust=NULL,
        extend = c("pad", "repeat", "reflect", "none"),
        gp = gpar(fill="transparent"),
        group = TRUE)

Arguments

`colours`	Two or more colours for the gradient to transition between.
`stops`	Locations of the gradient colours between the start and end points of the gradient (as a proportion of the distance from the start point to the end point).
`x1`, `y1`, `x2`, `y2`	The start and end points for a linear gradient.
`default.units`	The coordinate system to use if any location or dimension is specified as just a numeric value.
`extend`	What happens outside the start and end of the gradient (see Details).
`cx1`, `cy1`, `r1`, `cx2`, `cy2`, `r2`	The centre and radius of the start and end circles for a radial gradient.
`grob`	A grob (or a gTree) that will be drawn as the tile in a pattern fill.
`x`, `y`, `width`, `height`	The size of the tile for a pattern fill.
`just`, `hjust`, `vjust`	The justification of the tile relative to its location.
`gp`	Default graphical parameter settings for the tile.
`group`	A logical indicating whether the gradient or pattern is relative to the bounding box of the grob or whether it is relative to individual shapes within the grob.

Details

Use these functions to define a gradient fill or pattern fill and then use the resulting object as the value for fill in a call to the gpar() function.

The possible values of extend, and their meanings, are:

[pad:] propagate the value of the gradient at its boundary.
[none:] produce no fill beyond the limits of the gradient.
[repeat:] repeat the fill.
[reflect:] repeat the fill in reverse.

To create a tiling pattern, provide a simple grob (like a circle), specify the location and size of the pattern to include the simple grob, and specify extend="repeat".

On viewports, gradients and patterns are relative to the entire viewport, unless group = FALSE, in which case they are relative to individual grobs as they are drawn. On gTrees, gradients and patterns are relative to a bounding box around all of the children of the gTree, unless group = FALSE, in which case they are relative to individual children as they are drawn. On grobs, gradients and patterns are relative to a bounding box around all of the shapes that are drawn by the grob, unless group = FALSE, in which case they are relative to individual shapes.

Value

A linear gradient or radial gradient or pattern object.

Warning

Gradient fills and pattern fills are not supported on all graphics devices. Where they are not supported, closed shapes will be rendered with a transparent fill. Where they are supported, not all values of extend are supported.

On Cairo devices, use of clipping in the pattern definition should be avoided because it is very likely to result in distortion of the pattern tile.

Author(s)

Paul Murrell