Pressure profiles for hand-drawn strokes

Usage

pressure_flat(value = 1)

pressure_smooth(value = 1, taper = 1, turn_taper = 0.35)

pressure_human(
  value = 1,
  taper = 0.6,
  start = 0.35,
  end = 0.55,
  peak = 0.45,
  turn_taper = 0.35
)

pressure_dashed(value = 1, pattern = c(24, 12))

pressure_dashed_smooth(value = 1, pattern = c(24, 12), taper = 1)

Arguments

value: Maximum pressure supplied to the brush, in the range 0 to 1.
taper: How strongly pressure changes over the stroke. 0 keeps the pressure flat; 1 applies the full profile shape.
turn_taper: How strongly pressure is reduced at sharp turns.
start, end: Relative pressure at the start and end of a human-style stroke when taper = 1.
peak: Position of peak pressure along the stroke, in the range 0 to 1.
pattern: Alternating on/off dash lengths in device units. The default uses a 2:1 on/off ratio like base R's dashed line, at a moderate brush-scale length.

Value

A pressure-profile function for the pressure argument of hand() and human_hand(). Custom functions can also be supplied directly; they must accept t, normalized stroke progress in the range 0 to 1, turn in the range 0 to 1, and length, the total stroke length in device units. turn describes local path curvature: 0 is straight, larger values are sharper corners, and values near 1 are near reversals. Custom functions must be vectorized over t and turn, and return either length 1 or length(t).

Examples

plot.new()
plot.window(c(0, 10), c(0, 10))
draw_rough_lines(c(1, 9), c(8, 8), lwd = 5,
                 hand = hand(pressure = pressure_flat(0.5)))
draw_rough_lines(c(1, 9), c(5, 5), lwd = 5,
                 hand = hand(pressure = pressure_smooth()))
draw_rough_lines(c(1, 9), c(2, 2), lwd = 5,
                 hand = hand(pressure = pressure_human()))