terra (version 1.5-21)

stretch: Stretch

Description

Linear or histogram equalization stretch of values in a SpatRaster.

For linear stretch, provide the desired output range (minv and maxv) and the lower and upper bounds in the original data, either as quantiles (minq and maxq, or as cell values (smin and smax). If smin and smax are both not NA, minq and maxq are ignored.

For histogram equalization, these arguments are ignored, but you can provide the desired scale of the output.

Usage

# S4 method for SpatRaster
stretch(x, minv=0, maxv=255, minq=0, maxq=1, smin=NA, smax=NA,
		histeq=FALSE, scale=1, filename="", ...)

Arguments

x

SpatRaster

minv

numeric >= 0 and smaller than maxv. lower bound of stretched value

maxv

numeric <= 255 and larger than maxv. upper bound of stretched value

minq

numeric >= 0 and smaller than maxq. lower quantile bound of original value. Ignored if smin is supplied

maxq

numeric <= 1 and larger than minq. upper quantile bound of original value. Ignored if smax is supplied

smin

numeric < smax. user supplied lower value for the layers, to be used instead of a quantile computed by the function itself

smax

numeric > smin. user supplied upper value for the layers, to be used instead of a quantile computed by the function itself

histeq

logical. If TRUE histogram equalization is used instead of linear stretch

scale

numeric. The scale (maximum value) of the output if histeq=TRUE

filename

character. Output filename

...

additional arguments for writing files as in writeRaster

Value

SpatRaster

Examples

# NOT RUN {
r <- rast(nc=10, nr=10)
values(r) <- rep(1:25, 4)
rs <- stretch(r)
s <- c(r, r*2)
sr <- stretch(s)
# }