LT-GEE-TS-Animation-Annotation.R

# This script relies on the magick library, see this vignette for more information:
# https://cran.r-project.org/web/packages/magick/vignettes/intro.html
#
# If you have Windows or Mac OS, I believe ImageMagick STL is integrated with the CRAN distribution
# of the R magick library. If on Linux, see the "Build from source" section of the above URL
#
# This script will add year annotations from GIF animations generated and downloaded from the 
# LT-GEE Time Series Animator open access Earth Engine App: 
# https://emaprlab.users.earthengine.app/view/lt-gee-time-series-animator
#
# It will write out two files: one that goes forward in time only (*_fwd.gif) and
# one that goes forward and then backward in time (*_fwdbck.gif)
#
# 1. Copy this script into RStudio, make sure you have the magick library installed (in console: install.packages("magick"))
# 2. Edit the inputs using the example and inline comments to help
# 3. Select all lines and then press Crtl+Enter on your keyboard to run the script
# 4. The two files will be written to the same directory as the input file
# 5. Share the results widely and narrate what is happening in the video to provide context to viewers

library(magick)

####################################################################
# INPUTS
####################################################################

file = "C:/path/to/thumb.gif"  # system path for GIF file downloaded from: https://emaprlab.users.earthengine.app/view/lt-gee-time-series-animator
startYear = 1984               # define the start year used in the App
endYear = 2018                 # define the end year used in the App
bigger = 'yes'                 # would you like to make the GIF a little bigger? ('yes' or 'no')

####################################################################

yearRange = seq(startYear, endYear)

forward = image_read(file)

if(bigger == 'yes'){
  scaleIt = "425"
  if(image_info(forward[1])$height == 350) scaleIt = "x425"
  forward = image_scale(forward, scaleIt)
}

forward = forward %>% 
  image_despeckle(1) %>%
  image_blur(radius = 1, sigma = 0.2)

filled = c(forward[1])
comp = forward[1]
for(i in 2:length(yearRange)){
  comp = image_composite(comp,forward[i])
  filled = c(filled, comp)
}

for(i in 1:length(yearRange)){
  filled[i] = image_annotate(filled[i], as.character(yearRange[i]), size = 30, color = "white", gravity = "north", font="Helvetica")
}

forBack = c(filled, rev(filled))

image_write(filled, path = sub('.gif', '_fwd.gif', file), format = "gif")
image_write(forBack, path = sub('.gif', '_fwdbck.gif', file), format = "gif")