Description Usage Arguments Value Examples
View source: R/elevation_transparency.R
Turns overlay images transparent based on altitude. Can be used to create an image overlay that will only apply to valleys, or only to hills.
1 2 3 4 5 6 7 8 | elevation_transparency(
overlay_image,
raster_dem,
alpha_max = 0.4,
alpha_min = 0,
pct_alt_low = 0.05,
pct_alt_high = 0.25
)
|
overlay_image |
the image on which to alter transparency |
raster_dem |
elevation model raster file that will be used to adjust transparency |
alpha_max |
Transparency required at higher altitudes |
alpha_min |
Transparency required at lower altitudes |
pct_alt_low |
The percent of maximum altitude contained in raster_dem at which alpha_max will apply |
pct_alt_high |
The percent of maximum altitude contained in raster_dem at which alpha_min will apply |
An image with transparency defined by altitude
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | # elevation_transparency defaults to making hills transparent. Flip alpha_max
# and alpha_min values to reverse it.
#
# Transparency in the range between pct_alt_low and pct_alt_high will
# smoothly transition between alpha_max and alpha_min.
overlay_image <- elevation_shade(example_raster(), elevation_palette = c("#000000", "#FF0000"))
#Making hills transparent
ggmap_overlay_transparent_hills <- elevation_transparency(overlay_image,
example_raster(), alpha_max = 0.8, alpha_min = 0, pct_alt_low = 0.05,
pct_alt_high = 0.25)
# To make valleys transparent, flip alpha_max and alpha_min
ggmap_overlay_transparent_valleys <- elevation_transparency(overlay_image,
example_raster(), alpha_max = 0, alpha_min = 0.8, pct_alt_low = 0.05,
pct_alt_high = 0.25)
|
sh: 1: awk: Permission denied
There are NA values in raster_dem. Assuming they are min(raster_dem[], na.rm = TRUE) for shading.
sh: 1: awk: Permission denied
sh: 1: awk: Permission denied
sh: 1: awk: Permission denied
Warning messages:
1: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
2: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
3: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
4: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
5: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
6: In sweep(tile_raster@data@values, MARGIN = 2, STATS = tile_raster@data@max, :
STATS is longer than the extent of 'dim(x)[MARGIN]'
sh: 1: awk: Permission denied
There are NA values in raster_dem. Assuming they are min(raster_dem[], na.rm = TRUE) for shading.
sh: 1: awk: Permission denied
sh: 1: awk: Permission denied
Warning messages:
1: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
2: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
3: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
4: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
sh: 1: awk: Permission denied
There are NA values in raster_dem. Assuming they are min(raster_dem[], na.rm = TRUE) for shading.
sh: 1: awk: Permission denied
sh: 1: awk: Permission denied
Warning messages:
1: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
2: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
3: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
4: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
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