Calculate distance between 2 points in shiny - r

Question

I want to calculate the distance of the segment between 2 clicked points, i already have a function with that launches a shiny dashboard that allows you to save the clicks and draw a line between the pairs. It is printing the dimension of the image in pixels. Any image can be used changing the image_path.
I want to know if there is a way to select the segments of each pair and calculate the distance between them in pixels and later convert it to cm.
library(shiny)
library(shinydashboard)
library(dplyr)
library(imager)
library(reactable)
click_length <- function(image_path = system.file("example_images", package = "ClickMetrics")){
app <- shinyApp(
ui <- dashboardPage(
skin = 'purple',
dashboardHeader(title = "ClickMetrics"),
dashboardSidebar(disable = TRUE),
dashboardBody(
fluidRow(
box(plotOutput("IMG",
height = 400,
click = "click_plot")),
box(
(selectInput("IMAGE",
"Images:",
list.files(path = image_path,
pattern = ".jpg",
full.names = TRUE,
include.dirs = FALSE)))
),
actionButton("clear","Clear Points"),
reactableOutput("INFO")
)
)
),
server <- function(input, output, session){
# Creating a reactive value that receives image input
img <- reactive({
f <- input$IMAGE
imager::load.image(f)
})
# Store reactive values for coordinates
CLICKS <- reactiveValues(
x = NULL,
y = NULL,
n = NULL,
pair = NULL
)
ns <- session$ns
observeEvent(eventExpr = input$click_plot$x, handlerExpr = { ## Adds the info about clicks
CLICKS$x <- append(CLICKS$x, input$click_plot$x)
CLICKS$y <- append(CLICKS$y, input$click_plot$y)
CLICKS$n <- append(CLICKS$n, length(CLICKS$x))
CLICKS$pair <-
append(CLICKS$pair,
as.integer(ceiling(length(CLICKS$x)/2)))
df <- data.frame(CLICKS$x, CLICKS$y, CLICKS$pair)
df <- split(df, CLICKS$pair)
print(dim(img())) # prints dimensions of the image
})
output$IMG <- renderPlot({
expr = {
img <- img()
par(mar = c(0.5, 0.5, 1.75, 0.5))
plot(img, axes = FALSE)
box(col = 'gray')
mtext(text = input$IMAGE,
side = 3,
line = 0.5,
adj = 0.5,
cex = 1.23)
if (!is.null(CLICKS$x) && length(CLICKS$x) > 0) {
points(x = CLICKS$x,
y = CLICKS$y,
pch = 19,
cex = 0.75,
col = "red")
text(x = CLICKS$x,
y = CLICKS$y,
label = CLICKS$n,
pos = 3)
n_par <- 2 * floor(length(CLICKS$x)/2)
tb_pairs <- cbind(
matrix(CLICKS$x[1:n_par], ncol = 2, byrow = TRUE),
matrix(CLICKS$y[1:n_par], ncol = 2, byrow = TRUE))
segments(x0 = tb_pairs[, 1],
x1 = tb_pairs[, 2],
y0 = tb_pairs[, 3],
y1 = tb_pairs[, 4],
col = "black")
}
}
})
output$INFO <- renderReactable({
df1 <- data.frame(round(CLICKS$x,2), round(CLICKS$y,2), CLICKS$pair)
reactable(df1)
})
observe({ # clear clicked points
if(input$clear>0){
session$reload()
}
})
})
runApp(app)
}
click_length()
I tried some examples using locator, but it does not work inside a shiny dashboard, which i need.