feat(logo): add stamp_logo_png() to brand file-based PNG outputs

civilytics_logo()/make_logo_grob() brand ggplot/grobs, but flextables and other outputs are rendered to PNG first and can't use them. stamp_logo_png() is the raster analogue: it resolves the SAME brand asset that make_logo_grob() uses (via the type/variant switch) and composites it into a corner of an existing PNG in place, so file-based tables stay visually consistent with logo-branded plots. Dependency-free by design — uses only png + grid + grDevices (all already imported), no magick. Configurable type/variant/position/width/margin; preserves the image's pixel dimensions. Adds tests (21 assertions).
2026-06-22 16:33:08 -04:00
parent 41162597cf
commit 5fc8155965
4 changed files with 180 additions and 0 deletions
@@ -42,6 +42,7 @@ export(safe_ratio)
 export(scale_color_civilytics)
 export(scale_fill_civilytics)
 export(simpleCap)
+export(stamp_logo_png)
 export(star_subs)
 export(theme_civilytics)
 export(theme_civilytics_dark)
@@ -61,8 +62,12 @@ importFrom(ggplot2,annotation_custom)
 importFrom(ggplot2,ggplot)
 importFrom(ggplot2,theme)
 importFrom(ggplot2,theme_void)
+importFrom(grDevices,dev.off)
+importFrom(grDevices,png)
 importFrom(graphics,rasterImage)
 importFrom(grid,grid.draw)
+importFrom(grid,grid.newpage)
+importFrom(grid,grid.raster)
 importFrom(grid,rasterGrob)
 importFrom(gridExtra,arrangeGrob)
 importFrom(jpeg,readJPEG)
@@ -361,3 +361,92 @@ civilytics_logo <- function(plot,
           position = position)
 }

+
+#' Stamp the Civilytics logo onto a saved raster (PNG) image
+#'
+#' The raster analogue of [civilytics_logo()] for outputs that are already
+#' rendered to a file rather than held as a ggplot/grob — e.g. a `flextable`
+#' exported to PNG, or any `grDevices::png()` / `ragg::agg_png()` output.
+#' Resolves the *same* brand asset that [make_logo_grob()] uses, so file-based
+#' tables stay visually consistent with logo-branded plots, and composites it
+#' into a corner of the image. Pure base-graphics + grid + png — no new
+#' package dependencies.
+#'
+#' @param path Character. Path to the PNG to stamp. The file is overwritten
+#'   in place at its original pixel dimensions.
+#' @param type Character. `"wordmark"` (default) or `"mark"`. As in
+#'   [make_logo_grob()].
+#' @param variant Character. `"light"` (default, dark logo for light
+#'   backgrounds) or `"dark"` (reverse logo for dark backgrounds).
+#' @param position Character. Corner placement: `"bottom-right"` (default),
+#'   `"bottom-left"`, `"top-right"`, or `"top-left"`.
+#' @param width_frac Numeric. Logo width as a fraction of the image width
+#'   (default `0.15`). Height follows from the logo's aspect ratio.
+#' @param margin_frac Numeric. Padding from the edges as a fraction of the
+#'   image width (default `0.02`).
+#'
+#' @return `path`, invisibly.
+#' @export
+#' @importFrom png readPNG
+#' @importFrom grid grid.newpage grid.raster
+#' @importFrom grDevices png dev.off
+#' @examples
+#' \dontrun{
+#' # Brand a table exported to PNG so it matches civilytics_logo()-branded plots
+#' ragg::agg_png("table.png", width = 8, height = 4, units = "in", res = 200)
+#' plot(flextable::flextable(head(mtcars)))
+#' dev.off()
+#' stamp_logo_png("table.png")                         # wordmark, bottom-right
+#' stamp_logo_png("table.png", type = "mark", position = "bottom-left")
+#' }
+stamp_logo_png <- function(path,
+                           type = c("wordmark", "mark"),
+                           variant = c("light", "dark"),
+                           position = c("bottom-right", "bottom-left",
+                                        "top-right", "top-left"),
+                           width_frac = 0.15,
+                           margin_frac = 0.02) {
+  type     <- match.arg(type)
+  variant  <- match.arg(variant)
+  position <- match.arg(position)
+  stopifnot(file.exists(path))
+
+  # Same asset selection as make_logo_grob() so files match branded plots.
+  img_file <- switch(
+    paste(type, variant, sep = "_"),
+    wordmark_light = "civilytics-wordmark.png",
+    wordmark_dark  = "civilytics-wordmark-reverse.png",
+    mark_light     = "civilytics-mark.png",
+    mark_dark      = "civilytics-mark-reverse.png"
+  )
+  logo_path <- system.file("img", img_file, package = "civilytics")
+  if (!nzchar(logo_path)) {
+    stop("Civilytics logo asset not found in the 'civilytics' package: ", img_file)
+  }
+
+  base_img <- png::readPNG(path)        # height x width x channels, values in [0, 1]
+  logo_img <- png::readPNG(logo_path)
+  h <- dim(base_img)[1]
+  w <- dim(base_img)[2]
+  aspect <- dim(logo_img)[1] / dim(logo_img)[2]   # logo height / width
+
+  # Sizes/margins are expressed relative to image WIDTH, then converted to the
+  # device's npc units (which scale with the viewport's own width and height).
+  lw <- width_frac
+  lh <- width_frac * aspect * (w / h)
+  mx <- margin_frac
+  my <- margin_frac * (w / h)
+
+  x <- if (grepl("right", position)) 1 - mx else mx
+  y <- if (grepl("top",   position)) 1 - my else my
+  just <- c(if (grepl("right", position)) "right" else "left",
+            if (grepl("top",   position)) "top"   else "bottom")
+
+  grDevices::png(path, width = w, height = h, units = "px")
+  on.exit(grDevices::dev.off(), add = TRUE)
+  grid::grid.newpage()
+  grid::grid.raster(base_img, width = 1, height = 1, interpolate = FALSE)
+  grid::grid.raster(logo_img, x = x, y = y, width = lw, height = lh,
+                    just = just, interpolate = TRUE)
+  invisible(path)
+}
@@ -0,0 +1,56 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/logo.R
+\name{stamp_logo_png}
+\alias{stamp_logo_png}
+\title{Stamp the Civilytics logo onto a saved raster (PNG) image}
+\usage{
+stamp_logo_png(
+  path,
+  type = c("wordmark", "mark"),
+  variant = c("light", "dark"),
+  position = c("bottom-right", "bottom-left", "top-right", "top-left"),
+  width_frac = 0.15,
+  margin_frac = 0.02
+)
+}
+\arguments{
+\item{path}{Character. Path to the PNG to stamp. The file is overwritten
+in place at its original pixel dimensions.}
+
+\item{type}{Character. `"wordmark"` (default) or `"mark"`. As in
+[make_logo_grob()].}
+
+\item{variant}{Character. `"light"` (default, dark logo for light
+backgrounds) or `"dark"` (reverse logo for dark backgrounds).}
+
+\item{position}{Character. Corner placement: `"bottom-right"` (default),
+`"bottom-left"`, `"top-right"`, or `"top-left"`.}
+
+\item{width_frac}{Numeric. Logo width as a fraction of the image width
+(default `0.15`). Height follows from the logo's aspect ratio.}
+
+\item{margin_frac}{Numeric. Padding from the edges as a fraction of the
+image width (default `0.02`).}
+}
+\value{
+`path`, invisibly.
+}
+\description{
+The raster analogue of [civilytics_logo()] for outputs that are already
+rendered to a file rather than held as a ggplot/grob — e.g. a `flextable`
+exported to PNG, or any `grDevices::png()` / `ragg::agg_png()` output.
+Resolves the *same* brand asset that [make_logo_grob()] uses, so file-based
+tables stay visually consistent with logo-branded plots, and composites it
+into a corner of the image. Pure base-graphics + grid + png — no new
+package dependencies.
+}
+\examples{
+\dontrun{
+# Brand a table exported to PNG so it matches civilytics_logo()-branded plots
+ragg::agg_png("table.png", width = 8, height = 4, units = "in", res = 200)
+plot(flextable::flextable(head(mtcars)))
+dev.off()
+stamp_logo_png("table.png")                         # wordmark, bottom-right
+stamp_logo_png("table.png", type = "mark", position = "bottom-left")
+}
+}
@@ -0,0 +1,30 @@
+test_that("stamp_logo_png preserves image dimensions and returns the path invisibly", {
+  p <- tempfile(fileext = ".png")
+  on.exit(unlink(p), add = TRUE)
+  grDevices::png(p, width = 600, height = 240); plot(1:5); grDevices::dev.off()
+  in_dim <- dim(png::readPNG(p))[1:2]
+
+  expect_invisible(out <- stamp_logo_png(p))
+  expect_identical(out, p)
+  expect_identical(dim(png::readPNG(p))[1:2], in_dim)  # overwritten at same size
+})
+
+test_that("stamp_logo_png runs for every type/variant/position combination", {
+  p <- tempfile(fileext = ".png")
+  on.exit(unlink(p), add = TRUE)
+  grDevices::png(p, width = 500, height = 200); plot(1:5); grDevices::dev.off()
+
+  for (ty in c("wordmark", "mark")) {
+    for (va in c("light", "dark")) {
+      for (pos in c("bottom-right", "bottom-left", "top-right", "top-left")) {
+        expect_no_error(stamp_logo_png(p, type = ty, variant = va, position = pos))
+      }
+    }
+  }
+})
+
+test_that("stamp_logo_png validates its inputs", {
+  expect_error(stamp_logo_png(tempfile(fileext = ".png")))  # file does not exist
+  # invalid type is rejected by match.arg() before the file is touched
+  expect_error(stamp_logo_png(tempfile(fileext = ".png"), type = "banner"))
+})