R Shiny app to turn JPGs and PNGs into .ico favicon files. Written mostly by GPT o3-mini-high with help from Claude and Shiny Assistant (and me)

favicon_app.R

options(shiny.maxRequestSize = 5 * 1024^2)  # Limit uploads to 5 MB

library(shiny)
library(magick)
library(base64enc)
library(bslib)

# Helper function to sanitize file names
safeFileName <- function(filename) {
  gsub("[^a-zA-Z0-9_.-]", "_", filename)
}

ui <- page_fluid(
  theme = bs_theme(
    version = 5,
    bootswatch = "flatly",
    primary = "#2C3E50"
  ),
  
  tags$head(
    tags$style("
      .bg-white {
        background-image: linear-gradient(45deg, #ccc 25%, transparent 25%),
                         linear-gradient(-45deg, #ccc 25%, transparent 25%),
                         linear-gradient(45deg, transparent 75%, #ccc 75%),
                         linear-gradient(-45deg, transparent 75%, #ccc 75%);
        background-size: 20px 20px;
        background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
        background-color: white;
      }
    ")
  ),
  
  # Header card
  card(
    full_screen = FALSE,
    height = "auto",
    card_header(
      class = "bg-primary text-white",
      h1("PNG/JPG to ICO Favicon Converter", class = "mb-0")
    ),
    p(
      class = "text-muted mt-2",
      "Written mostly by ",
      tags$a(
        href = "https://openai.com/index/openai-o3-mini/",
        target = "_blank",
        "OpenAI o3-mini-high",
        class = "text-decoration-none"
      ),
      ". Design suggested by ",
      tags$a(
        href = "https://gallery.shinyapps.io/assistant",
        target = "_blank",
        "Shiny Assistant",
        class = "text-decoration-none"
      ),
      ". View code on GitHub gist: ",  # Note the added space and comma here
      tags$a(
        href = "https://gist.github.com/smach/b1669e05d5ead993bcb62839d4a738de",  # Replace with your actual gist URL
        target = "_blank",
        class = "text-decoration-none",
        icon("github"),  # This adds the GitHub icon
        ""  # Text that appears after the icon
      )
    )
  ),
  
  layout_columns(
    col_widths = c(4, 8),
    gap = "1rem",
    
    # Input controls card
    card(
      card_header("Settings"),
      card_body(
        fileInput("file", "Choose PNG or JPG File",
                  accept = c("image/png", "image/jpeg")),
        checkboxGroupInput("sizes", "Select favicon sizes (pixels):",
                           choices = list("16x16" = 16, "32x32" = 32,
                                          "48x48" = 48, "64x64" = 64),
                           selected = 32),
        downloadButton("download", "Download Favicon File(s)", 
                       class = "btn-primary btn-lg w-100")
      )
    ),
    
    # Preview card
    card(
      card_header("Previews"),
      card_body(
        uiOutput("img_previews")
      )
    )
  )
)

server <- function(input, output, session) {
  
  # Reactive expression to safely read the uploaded image
  img_reactive <- reactive({
    req(input$file)
    
    if (!input$file$type %in% c("image/png", "image/jpeg")) {
      stop("Uploaded file must be a PNG or JPG image.")
    }
    
    img <- tryCatch({
      image_read(input$file$datapath)
    }, error = function(e) {
      stop("Could not read image. Please ensure the file is a valid image.")
    })
    
    img
  })
  
  # Reactive expression to generate preview images
  preview_images <- reactive({
    req(input$file, input$sizes)
    sizes <- as.numeric(input$sizes)
    raw_img <- img_reactive()
    
    lapply(sizes, function(sz) {
      img_scaled <- image_scale(raw_img, paste0(sz, "x", sz))
      tmpfile <- tempfile(fileext = ".png")
      image_write(img_scaled, path = tmpfile, format = "png")
      uri <- dataURI(file = tmpfile, mime = "image/png")
      list(size = sz, uri = uri)
    })
  })
  
  # Dynamic UI for previews
  output$img_previews <- renderUI({
    req(preview_images())
    images <- preview_images()
    
    tagList(
      div(
        class = "d-flex flex-wrap gap-4 justify-content-center",
        lapply(images, function(img_info) {
          div(
            class = "text-center preview-container",
            style = "min-width: 100px;",
            h4(paste0(img_info$size, " × ", img_info$size)),
            div(
              class = "transparency-grid border rounded p-3",
              style = sprintf("width: %dpx; height: %dpx; display: flex; align-items: center; justify-content: center;",
                              img_info$size + 40, img_info$size + 40),
              img(
                src = img_info$uri,
                width = img_info$size,
                height = img_info$size,
                style = "image-rendering: pixelated;"
              )
            )
          )
        })
      )
    )
  })
  
  # Download handler
  output$download <- downloadHandler(
    filename = function() {
      req(input$file)
      base <- safeFileName(tools::file_path_sans_ext(basename(input$file$name)))
      sizes <- as.numeric(input$sizes)
      if (length(sizes) == 1) {
        paste0(base, "_", sizes, "x", sizes, ".ico")
      } else {
        paste0(base, "_favicons.zip")
      }
    },
    content = function(file) {
      req(input$file, input$sizes)
      sizes <- as.numeric(input$sizes)
      raw_img <- img_reactive()
      
      if (length(sizes) == 1) {
        sz <- sizes[1]
        img_scaled <- image_scale(raw_img, paste0(sz, "x", sz))
        image_write(img_scaled, path = file, format = "ico")
      } else {
        tmpDir <- tempdir()
        ico_files <- sapply(sizes, function(sz) {
          out_file <- file.path(tmpDir, paste0(
            safeFileName(tools::file_path_sans_ext(basename(input$file$name))),
            "_", sz, "x", sz, ".ico"
          ))
          img_scaled <- image_scale(raw_img, paste0(sz, "x", sz))
          image_write(img_scaled, path = out_file, format = "ico")
          out_file
        })
        
        oldwd <- getwd()
        setwd(tmpDir)
        on.exit(setwd(oldwd), add = TRUE)
        
        zip_file <- file.path(tmpDir, "favicons.zip")
        utils::zip(zipfile = zip_file, files = basename(ico_files))
        file.copy(zip_file, file)
      }
    }
  )
}

shinyApp(ui, server)