R/ee_as_thumbnail.R
ee_as_thumbnail.RdWrapper function around ee$Image$getThumbURL to create a stars or
RasterLayer R object from a
EE thumbnail image.
ee_as_thumbnail(
image,
region,
dimensions,
vizparams = NULL,
raster = FALSE,
quiet = FALSE
)EE Image object to be converted into a stars object.
EE Geometry Rectangle (ee$Geometry$Rectangle) specifies the region to be exported. The CRS must match the 'x' argument; otherwise, it will be forced.
Numeric vector of length 2 that specifies the dimensions of the thumbnail image in pixels. If only one integer is provided, it determines the size of the larger dimension of the image and scales the other dimension proportionally. Defaults to 512 pixels for the larger image aspect dimension.
A list containing the visualization parameters.See details.
Logical. Should the thumbnail image be saved as a RasterStack object?
logical; suppress info messages.
An stars or Raster object depending on the raster argument.
vizparams set up the details of the thumbnail image. With
ee_as_thumbnail allows exporting only one-band (G) or three-band
(RGB) images. Several parameters can be passed on to control color,
intensity, the maximum and minimum values, etc. The table below provides
all the parameters that admit ee_as_thumbnail.
| Parameter | Description | Type |
| bands | Comma-delimited list of three band (RGB) | list |
| min | Value(s) to map to 0 | number or list of three numbers, one for each band |
| max | Value(s) to map to 1 | number or list of three numbers, one for each band |
| gain | Value(s) by which to multiply each pixel value | number or list of three numbers, one for each band |
| bias | Value(s) to add to each Digital Number value | number or list of three numbers, one for each band |
| gamma | Gamma correction factor(s) | number or list of three numbers, one for each band |
| palette | List of CSS-style color strings (single-band only) | comma-separated list of hex strings |
| opacity | The opacity of the layer (from 0 to 1) | number |
Other image download functions:
ee_as_raster(),
ee_as_rast(),
ee_as_stars(),
ee_imagecollection_to_local()
if (FALSE) {
library(raster)
library(stars)
library(rgee)
ee_Initialize()
nc <- st_read(system.file("shp/arequipa.shp", package = "rgee"))
dem_palette <- c(
"#008435", "#1CAC17", "#48D00C", "#B3E34B", "#F4E467",
"#F4C84E", "#D59F3C", "#A36D2D", "#C6A889", "#FFFFFF"
)
## DEM data -SRTM v4.0
image <- ee$Image("CGIAR/SRTM90_V4")
world_region <- ee$Geometry$Rectangle(
coords = c(-180,-60,180,60),
proj = "EPSG:4326",
geodesic = FALSE
)
## world - elevation
world_dem <- ee_as_thumbnail(
image = image,
region = world_region,
dimensions = 1024,
vizparams = list(min = 0, max = 5000)
)
world_dem[world_dem <= 0] <- NA
world_dem <- world_dem * 5000
plot(
x = world_dem, col = dem_palette, breaks = "equal",
reset = FALSE, main = "SRTM - World"
)
## Arequipa-Peru
arequipa_region <- nc %>%
st_bbox() %>%
st_as_sfc() %>%
sf_as_ee()
arequipa_dem <- ee_as_thumbnail(
image = image,
region = arequipa_region$buffer(1000)$bounds(),
dimensions = 512,
vizparams = list(min = 0, max = 5000)
)
arequipa_dem <- arequipa_dem * 5000
st_crs(arequipa_dem) <- 4326
plot(
x = arequipa_dem[nc], col = dem_palette, breaks = "equal",
reset = FALSE, main = "SRTM - Arequipa"
)
suppressWarnings(plot(
x = nc, col = NA, border = "black", add = TRUE,
lwd = 1.5
))
dev.off()
## LANDSAT 8
img <- ee$Image("LANDSAT/LC08/C01/T1_SR/LC08_038029_20180810")$
select(c("B4", "B3", "B2"))
Map$centerObject(img)
Map$addLayer(img, list(min = 0, max = 5000, gamma = 1.5))
## Teton Wilderness
l8_img <- ee_as_thumbnail(
image = img,
region = img$geometry()$bounds(),
dimensions = 1024,
vizparams = list(min = 0, max = 5000, gamma = 1.5),
raster = TRUE
)
crs(l8_img) <- "+proj=longlat +datum=WGS84 +no_defs"
plotRGB(l8_img, stretch = "lin")
}