image_data_extraction.R

library(magick)
library(tidyverse)

im <- image_read("line.jpg")

im_proc <- im %>%
    image_channel("saturation") %>%
    image_threshold("white", "30%") %>%
    image_negate()

dat <- image_data(im_proc)[1,,] %>%
    as.data.frame() %>%
    mutate(Row = 1:nrow(.)) %>%
    select(Row, everything()) %>%
    mutate_all(as.character) %>%
    gather(key = Column, value = value, 2:ncol(.)) %>%
    mutate(Column = as.numeric(gsub("V", "", Column)),
           Row = as.numeric(Row),
           value = ifelse(value == "00", NA, 1)) %>%
    filter(!is.na(value))

ggplot(data = dat, aes(x = Row, y = Column, colour = (Column < 300))) +
    geom_point() +
    scale_y_continuous(trans = "reverse") +
    scale_colour_manual(values = c("red4", "blue4")) +
    theme(legend.position = "off")