Geolocating and writing many TIFFs at same time using R

Question

I have found a way to give a PNG the CRS and location of a geolocated TIFF, and to convert the PNG to TIFF. Now I have to apply it to different PNGs in the same folder (all named Pt6_frame1, Pt6_frame2, etc.) and write the individual new TIFF files as Pt6_frame1_geolocated, Pt6_frame2_geolocated, etc. Does anyone have an idea of how to do so? I have tried the code in various posts, using for loops and functions, but I get various errors.

## Loading image of interest as stack

R_test <- 
  stack("Pt6_clear.png")

# Give image of interest the lat/lon coords of the geolocated image as appear in its metadata in the console

extent(R_test) <- c(-9073461, -9073269, 2974255, 2974366)

# Copy the projection data of the geolocated image as appears in the console to the image of interest

projection(R_test) <- CRS("+proj=merc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs")

## Write new geolocated image into a file

writeRaster(R_test, "R_test_geolocated.tif",
            format="GTiff",
            overwrite=TRUE,
            NAflag=-9999) 

Answer 1

Solved!

library(raster)
library(rgdal)
library(ggplot2)
library(dplyr)
library(OpenImageR)

geolocate <- function(input) {
## Loading image of interest as raster
R_test <- 
  stack(input)
R_test ## It does not have any CRS
plot(R_test)

# Give image of interest the lat/lon coords of the geolocated image as appear in its metadata in the console
extent(R_test) <- c(-9073461, -9073269, 2974255, 2974366)
# Copy the projection data of the geolocated image as appears in the console to the image of interest 
projection(R_test) <- CRS("+proj=merc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs")

## Write new geolocated image into a file

writeRaster(R_test,
            filename=sub(".png", "_geolocated.tif", input),
            format="GTiff",
            overwrite=TRUE,
            NAflag=-9999)
}


filenames <- list.files(path = ".",  #The point means the working directory
                        # Now follows a regular expression that matches:
                        pattern = ".png",
                        full.names = TRUE)
for (f in filenames) {
  geolocate(f)
}