Creating a mp4 of satellite images

Creating mp4 of satellite images

This assumes that you already have all the images in a directory.

Load the packages.

library(ggplot2) # plotting
library(magick) # for image_* functions

Step 1. Install FFmpeg if needed

Here is how to do it on a Mac (MacOS Sierra 10.12.6); Google to figure this out for Windows or Unix.

1. Open up utilities (in apps), and open Terminal.
   

2. Type the following on the command line to install brew

   ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go/install)"

3. Then you can install FFmpeg with this command.

   brew install ffmpeg

Make animation with animation and FFmpeg

library(animation)
fil_dir = "wheremypngsare"
imgs <- list.files(path=fil_dir,pattern="*.png", full.names = T)
saveVideo({
  for(img in imgs){
    im <- magick::image_read(img)
    plot(as.raster(im))
  }
},
video.name="myanimation.mp4"
)

The problem is that the mp4 is low quality. You can change that but you need to dig into the documentation for FFmpeg.

Alternative. Use free gif to mp4 converter

Make a gif and then upload to A free gif to mp4 converter like this one.

More complicated example

I wanted to merge 4 images from 4 years and have a legend at the bottom. Here’s how I did it using ImageMagick to make a big gif (13M) and then uploaded that to ezgif.com to make a much smaller movie.

The code

Here is the code I used

# get the names of each file
imgs=list()
for(j in 1:4){
  year=as.character(2014:2017)[j]
  fil_dir <- paste0("india_sst_pngs_",year)
  imgs[[j]] = list.files(path = fil_dir, pattern = "*.png", full.names = T)
}

# Then make the gif
img = c()
imgleg = image_read("legend.png")
  for(i in 1:length(imgs[[1]])){
    theimgs=list()
    for(j in 1:4){
      theimgs[[j]]=image_read(imgs[[j]][i])
      theimgs[[j]] = image_crop(theimgs[[j]], geometry_area(width = 230, height = 332, x_off = 28, y_off = 0))
    }
    imtop <- image_append(image_join(theimgs[[1]],theimgs[[2]]))
    imbot <- image_append(image_join(theimgs[[3]],theimgs[[4]]))
    im <- magick::image_append(image_join(imtop, imbot, imgleg), stack=TRUE)
    img <- image_join(img, im)
  }
imggif = image_animate(img, fps=4, loop=1)
image_write(imggif, "Kochin_SST_2014-17_4x4.gif")

I could also do the same with animation

# you can use animation package but the default settings give a low quality movie
library(animation)
library(magick)
imgleg = image_read("legend.png")
saveVideo({
  for(i in 1:length(img14)){
    theimgs=list()
    for(j in 1:4){
      theimgs[[j]]=image_read(imgs[[j]][i])
      theimgs[[j]] = image_crop(theimgs[[j]], geometry_area(width = 230, height = 332, x_off = 28, y_off = 0))
    }
    imtop <- image_append(image_join(theimgs[[1]],theimgs[[2]]))
    imbot <- image_append(image_join(theimgs[[3]],theimgs[[4]]))
    im <- magick::image_append(image_join(imtop, imbot, imgleg), stack=TRUE)
    plot(as.raster(im))
  }
  },
video.name="Kochin_SST_2014-17.mp4"
)