---
title: "Warp Affine using R"
author: "Lampros Mouselimis"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Warp Affine using R}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---


The **getAffineTransform()** and **warpAffine()** functions of the OpenImageR package is an RcppArmadillo re-implementation of [existing Python Code](https://github.com/OlehOnyshchak/ImageTransformations/blob/master/AffineTransformation.ipynb) and this vignette shows how these functions can be used from within R based on the [author's .ipynb](https://github.com/OlehOnyshchak/ImageTransformations/blob/master/AffineTransformation.ipynb) file

<br>

```{r, eval = T}

require(OpenImageR)

path = system.file('tmp_images', 'landscape.jpg', package = "OpenImageR")

img = readImage(path)
print(dim(img))

```

<br>

```{r, out.width = "65%", out.height = "50%", fig.align = 'center', fig.cap = "Input Image", fig.alt="Input Image", echo = F, eval = T}

knitr::include_graphics(path)

```

<br>

```{r, eval = T}

r = ncol(img)
c = nrow(img)
offset = 50

original_points = matrix(data = c(0, 0, r, 0, 0, c),
                         nrow = 3,
                         ncol = 2,
                         byrow = TRUE)

transformed_points = matrix(data = c(offset, 0, r, offset, 0, c-offset),
                            nrow = 3,
                            ncol = 2,
                            byrow = TRUE)

M_aff = getAffineTransform(original_points = original_points,
                           transformed_points = transformed_points)

```

<br>

The following is the Affine transformation matrix,

```{r, eval = T}

print(M_aff)

```

<br>

The Affine transformation matrix can be used as input in the *warpAffine()* function,

```{r, eval = T}

res_3d = warpAffine(img = img,
                    M = M_aff,
                    R = r,
                    C = c,
                    verbose = TRUE)

str(res_3d)

```

<br>

The next image shows the output based on the input data and parameters,

```{r, out.width = "65%", out.height = "50%", fig.align = 'center', fig.cap = "Output of Warp Affine function", fig.alt="Output of Warp Affine function", echo = T, eval = T}

imageShow(res_3d, clear_viewer = FALSE)

```

<br>