Image to data frame to ggplot heatmap

Image to DF to ggplot

Steve de Peijper

25 mei 2016

In this post we will convert an image to a dataframe to display the image with ggplot. In a later post we will compress the image.

library("png", lib.loc="C:/TFS/Rlib/")
require(ggplot2)

## Loading required package: ggplot2

This is the original image:

.

The work

plaatje = readPNG("c:/TFS/test.png")
x <- data.frame(1:100,1,1,1,1,1)
colnames(x) = c("t", "x","y", "r", "g", "b")
for (a in 1:3) {
  teller = 1
  for (i in 1:length(plaatje[,1,a])) { #Hoogte
    for (j in 1:length(plaatje[i,,a])) { #Breedte
      x[teller,c(1:3,3+a)]  = c(teller,j,i,plaatje[i,j,a])
      teller = teller + 1
    } 
  }
}


ggplot(data=x, aes(x=x, y=y, fill=rgb(r,g,b))) +
  geom_tile() +
  scale_fill_identity()