library(raster)

## Loading required package: sp

library(sf)

## Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 7.0.0

# Raster
r = brick("/home/michael/Dropbox/Courses/R_2019/data/landsat_04_10_2000.tif")

# Points
p1 = st_point(c(670000, 3470000))
p2 = st_point(c(680000, 3480000))
p3 = st_point(c(681000, 3475000))
p4 = st_point(c(671000, 3465000))

# Polygon
pol = c(p1, p2, p3, p4)
pol = st_cast(pol, "POLYGON")

# Plot 1 - before
plotRGB(r, r = 3, g = 2, b = 1, scale = 1)
plot(pol, add = TRUE, border = "red")

# Crop
r = mask(r, as(pol, "Spatial"))

# Plot 2 - after
plotRGB(r, r = 3, g = 2, b = 1, scale = 1)
plot(pol, add = TRUE, border = "red")