Convert images to/from native raster image format

library(grid)
library(nara)

Create a native raster image

nr <- nr_new(10, 10, fill = 'white')
class(nr)
#> [1] "nativeRaster"

Save/Load native raster images to/from PNG and JPEG

The fastpng, png and jpeg packages allow images to be loaded directly as native raster images.

png_file <- system.file("image", "deer-1.png", package="nara")
jpg_file <- system.file("image", "deer-1.jpg", package="nara")

nr <- fastpng::read_png(png_file, type = 'nativeraster')
class(nr)
#> [1] "nativeRaster"
plot(nr)

nr <- png::readPNG(png_file, native = TRUE)
class(nr)
#> [1] "nativeRaster"
plot(nr)

nr <- jpeg::readJPEG(jpg_file, native = TRUE)
class(nr)
#> [1] "nativeRaster"
plot(nr)

These packages will also automatically detect and save native raster images

fastpng::write_png(nr, "test.png")
jpeg::writeJPEG(nr, "test.jpg")
png::writePNG(nr, "test.png")

Convert a regular R raster image to/from native raster image format

ras <- matrix(c('brown', 'darkblue', 'darkblue', 'brown'), 2, 2)
ras
#>      [,1]       [,2]      
#> [1,] "brown"    "darkblue"
#> [2,] "darkblue" "brown"
class(ras)
#> [1] "matrix" "array"
grid.raster(ras, interpolate = FALSE)

nr <- nara::raster_to_nr(ras)
nr
#> <nativeRaster> object: rows:2  cols:2
class(nr)
#> [1] "nativeRaster"
plot(nr)

Convert a regular R array image to/from native raster image format

arr <- array(c(
  1, 1, 0,
  0, 0, 0,
  0, 0, 0, 
  1, 1, 0
), dim = c(2, 2, 3))

arr
#> , , 1
#> 
#>      [,1] [,2]
#> [1,]    1    0
#> [2,]    1    0
#> 
#> , , 2
#> 
#>      [,1] [,2]
#> [1,]    0    0
#> [2,]    0    0
#> 
#> , , 3
#> 
#>      [,1] [,2]
#> [1,]    0    1
#> [2,]    1    0
class(arr)
#> [1] "array"
grid.raster(arr, interpolate = FALSE)

nr <- nara::array_to_nr(arr)
nr
#> <nativeRaster> object: rows:2  cols:2
class(nr)
#> [1] "nativeRaster"
plot(nr)