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

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

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


## Create a native raster image

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



## 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.


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



```{r}
nr <- fastpng::read_png(png_file, type = 'nativeraster')
class(nr)
plot(nr)
```


```{r}
nr <- png::readPNG(png_file, native = TRUE)
class(nr)
plot(nr)
```

```{r}
nr <- jpeg::readJPEG(jpg_file, native = TRUE)
class(nr)
plot(nr)
```


These packages will also automatically detect and save native raster images

```{r eval=FALSE}
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

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


```{r}
nr <- nara::raster_to_nr(ras)
nr
class(nr)
plot(nr)
```

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

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

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

```{r}
nr <- nara::array_to_nr(arr)
nr
class(nr)
plot(nr)
```