Package 'pixels'

Tools for Working with Image Pixels

Description

This package provides tools to show and draw image pixels using 'HTML' widgets and 'Shiny' applications.

Details

This package can be used to: Visualize the 'MNIST' dataset for handwritten digit recognition, create simple test cases for image classification, or to create new datasets by building a 'Shiny' applicaiton that enables many users to capture images for supervised learning.

Author(s)

Maintainer: Javier Luraschi [email protected]

Other contributors:

• RStudio [copyright holder]

See Also

Useful links:

• https://github.com/javierluraschi/pixels

• Report bugs at https://github.com/javierluraschi/pixels/issues

---

Gets Pixels

Description

Creates an ShinyGadget to retrieve pixels.

Usage

get_pixels(pixels = NULL, grid = c(28, 28), size = c(250, 250),
  brush = matrix(c(0, 0.5, 0.8, 0.5, 0, 0.5, 1, 1, 1, 0.5, 0.8, 1, 1, 1, 0.8,
  0.5, 1, 1, 1, 0.5, 0, 0.5, 0.8, 0.5, 0), 5, 5), params = list(fill =
  list(color = "#555555"), grid = list(color = "#EEEEEE")))

Arguments

pixels	The pixels to render as a 1-dimensional vector, row-first order expected.
grid	The grid dimensions specified as a vector.
size	The canvas dimensions specified as a vector.
brush	The brush specified as a matrix.
params	A set of parameters to customize the visual appearance. #' @examples library(pixels) if (interactive()) get_pixels()

---

Shiny Widget Output

Description

Provides a Shiny Widget for Output.

Usage

shiny_pixels_output(outputId, width = "100%", height = "400px")

Arguments

outputId	The identifier for this widget.
width	The width for this widget.
height	The height for this widget.

Examples

library(shiny)

ui <- fluidPage(
  tags$head(
    tags$style(HTML("
      #pixels {
        height: 270px !important;
        margin-top: 10px;
      }
    "))
  ),
  titlePanel("Digit Capture Application"),
  textOutput("prompt"),
  shiny_pixels_output("pixels"),
  actionButton("captureDigit", "Capture")
)

server <- function(input, output) {
  output$pixels <- shiny_render_pixels(
    show_pixels()
  )

  digit <- reactiveVal(floor(runif(1, 1, 10)))
  output$prompt <- renderText(paste0("Please draw number ", digit(), ":"))

  observeEvent(input$captureDigit, {
    digit_path <- file.path("digits", digit())
    if (!dir.exists(digit_path)) dir.create(digit_path, recursive = TRUE)
    saveRDS(input$pixels, paste0(digit_path, "/", as.numeric(Sys.time()), ".rds"))
 
    digit(floor(runif(1, 1, 10)))
    output$pixels <- shiny_render_pixels(
      show_pixels()
    )
  })
}

if (interactive()) {
  shinyApp(ui = ui, server = server)
}

---

Shiny Widget Render

Description

Renders the Shiny Widget.

Usage

shiny_render_pixels(expr, env = parent.frame(), quoted = FALSE)

Arguments

expr	The expr for shinyRenderWidget.
env	The env for shinyRenderWidget.
quoted	The quoted for shinyRenderWidget.

See Also

[shiny_pixels_output()] for an example of using this function within a 'Shiny' application.

---

Show Pixels

Description

Creates an HTMLWidget to show pixels.

Usage

show_pixels(pixels = NULL, grid = c(28, 28), size = c(250, 250),
  brush = matrix(c(0, 0.5, 0.8, 0.5, 0, 0.5, 1, 1, 1, 0.5, 0.8, 1, 1, 1, 0.8,
  0.5, 1, 1, 1, 0.5, 0, 0.5, 0.8, 0.5, 0), 5, 5), params = list(fill =
  list(color = "#555555"), grid = list(color = "#EEEEEE")))

Arguments

pixels	The pixels to render as a 1-dimensional vector, row-first order expected.
grid	The grid dimensions specified as a c(width, height) vector.
size	The canvas dimensions specified as a c(width, height) vector.
brush	The brush specified as a matrix.
params	A set of parameters to customize the visual appearance.

Examples

library(pixels)
show_pixels(
  round(runif(400, 0, 1)),
  grid = c(40, 10),
  size = c(800, 200),
  params = list(fill = list(color = "#FF3388"))
)

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