R/ee_as_thumbnail.R
ee_as_thumbnail.Rd
Wrapper 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 )
image | EE Image object to be converted into a stars object. |
---|---|
region | EE Geometry Rectangle ( |
dimensions | Numeric vector of length 2. Thumbnail dimensions in pixel units. If a single integer is provided, it defines the size of the image's larger aspect dimension and scales the smaller dimension proportionally. Defaults to 512 pixels for the larger image aspect dimension. |
vizparams | A list that contains the visualization parameters. See details. |
raster | Logical. Should the thumbnail image be saved as a RasterStack object? |
quiet | 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
only is possible export 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 names to be mapped to 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 (DN) 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 images only) | comma-separated list of hex strings |
opacity | The opacity of the layer (0.0 is fully transparent and 1.0 is fully opaque) | number |
Other image download functions:
ee_as_raster()
,
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)$bounds(), dimensions = 512, vizparams = list(min = 0, max = 5000) ) arequipa_dem <- arequipa_dem * 5000 plot( x = arequipa_dem[nc], col = dem_palette, breaks = "equal", reset = FALSE, main = "SRTM - Arequipa" ) suppressWarnings(plot( x = nc, col = NA, border = "black", add = TRUE, lwd = 1.5 )) dev.off() ## LANDSAT 8 img <- ee$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 ) plotRGB(l8_img, stretch = "lin") }