How to get images from the .tex folder (relative path) in Rmarkdown? - r

Question

I'm trying to get a watermark image like here:
How to add a watermark image on rmarkdown?
I almost did it, but as I wrote on my original question the background.png image that the \includegraphics get comes from C:\Program Files (x86)\MiKTeX 2.9\tex\plain\present
I'm currently using my Latex code from an external file using the follwing at beginning of my .Rmd:
output:
pdf_document:
includes:
in_header: header.tex
And in header.tex I'm using the following code:
\usepackage{eso-pic,graphicx,transparent}
\AddToShipoutPictureFG{
\put(0,0){%
\parbox[b][\paperheight]{\paperwidth}{%
\centering
{\transparent{0.3} \includegraphics[width=\paperwidth,height=\paperheight,%
keepaspectratio]{background.png}}%
}
}
}
But I just can't get the background.png from where my .tex file is (that is the same that my .Rmd file is).
How I tell to my .tex file get this image from the relative path to my .tex?
--EDIT--
I'm using the render function from rmarkdown to make the report, follow is a screenshot from the insides of my folder with .Rmd, the .tex file and the error when I try to insert a test.png:

Answer 1

"It works for me." Here is a minimal Rmarkdown file, trimmed down from one of the templates offered by RStudio:
---
title: "Demo"
author: "Dirk"
date: "October 3, 2016"
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## R Markdown
This is an R Markdown document. We include one figure
\includegraphics{Rlogo.png}
La fin.
I can hit the knit button just fine, or run this by hand:
/tmp$ cat includeDemo.Rmd
---
title: "Demo"
author: "Dirk"
date: "October 3, 2016"
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## R Markdown
This is an R Markdown document. We include one figure
\includegraphics{Rlogo.png}
La fin.
/tmp$ Rscript -e 'rmarkdown::render("includeDemo.Rmd")'
processing file: includeDemo.Rmd
|...................... | 33%
ordinary text without R code
|........................................... | 67%
label: setup (with options)
List of 1
$ include: logi FALSE
|.................................................................| 100%
ordinary text without R code
output file: includeDemo.knit.md
/usr/bin/pandoc +RTS -K512m -RTS includeDemo.utf8.md --to latex --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash --output includeDemo.pdf --template /usr/local/lib/R/site-library/rmarkdown/rmd/latex/default-1.15.2.tex --highlight-style tango --latex-engine pdflatex --variable graphics=yes --variable 'geometry:margin=1in'
Output created: includeDemo.pdf
/tmp$
Maybe something is playing tricks with you by switching from the current directory to a temporary processing directory. In which an (icky!!) absolute path may help...

Answer 2

I just did it.
The problem were on MiKTeX for Windows.
I just followed the steps on this answer, remembering to assure that the folder is TDS-compliant (with a tex folder in it), and after I just put the image on the tex folder.