---
title: "Convert images to/from nativeRaster"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Convert images to/from nativeRaster}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

```{r setup}
library(grid)
library(nara)
```


## Create a `nativeRaster`

```{r}
nr <- nr_new(10, 10, fill = 'white')
class(nr)
```



## Save/Load `nativeRaster` images to/from PNG and JPEG

Both the `{png}` and `{jpeg}` packages allow images to be loaded directly 
as `nativeRaster` images.

```{r}
img <- jpeg::readJPEG(system.file("img", "Rlogo.jpg", package="jpeg"), native = TRUE)
class(img)
grid.raster(img, interpolate = FALSE)
```


```{r}
img <- png::readPNG(system.file("img", "Rlogo.png", package="png"), native = TRUE)
class(img)
grid.raster(img, interpolate = FALSE)
```


```{r eval=FALSE}
# {jpeg} and {png} will automatically detect and save 'nativeRaster' images
jpeg::writeJPEG(img, "test.jpg")
png::writePNG(img, "test.png")
```

## Convert a regular R `raster` image to/from `nativeRaster`

```{r}
ras <- matrix(c('brown', 'darkblue', 'darkblue', 'brown'), 2, 2)
ras
grid.raster(ras, interpolate = FALSE)
```


```{r}
nr <- nara::raster_to_nr(ras)
nr
grid.raster(nr, interpolate = FALSE)
```

## Convert a regular R `array` image to/from `nativeRaster`

```{r}
arr <- array(c(
  1, 1, 0,
  0, 0, 0,
  0, 0, 0, 
  1, 1, 0
), dim = c(2, 2, 3))

arr
grid.raster(arr, interpolate = FALSE)
```

```{r}
nr <- nara::array_to_nr(arr)
nr
grid.raster(nr, interpolate = FALSE)
```