Render a PDF page to a bitmap

Rasterises one page of a PDF document via PDFium and returns a pdfium_bitmap object (an integer matrix that inherits from base R's nativeRaster class). Use graphics::plot() for an immediate-display path (the S3 method here routes through grid::grid.raster() on a 3-D RGBA array, the one R-engine combination that renders pixel-for-pixel correctly across platforms). Conversion helpers (as.raster.pdfium_bitmap(), as.array.pdfium_bitmap(), as.matrix.pdfium_bitmap()) cover the other common bitmap shapes downstream packages expect.

Usage

pdf_render_page(
  page,
  page_num = 1L,
  dpi = 72,
  background = "white",
  annotations = FALSE,
  rotation = 0L
)

Arguments

page

A pdfium_page from pdf_page_load(), or a pdfium_doc (the page given by page_num will be loaded and closed internally).

page_num

One-based page index. Only used when page is a pdfium_doc. Ignored otherwise.

dpi

Render resolution in dots per inch (default 72, meaning one pixel per PDF point). Higher values give larger, sharper output at proportional memory cost.

background

Background color drawn behind the page content before rendering. Accepts any string grDevices::col2rgb() understands (named color, "#RRGGBB", "#RRGGBBAA"), or NA for a fully transparent background. Defaults to "white".

annotations

Logical; render annotation appearance streams on top of the page content. Defaults to FALSE.

rotation

Extra rotation in degrees applied on top of the page's own /Rotate attribute. One of 0, 90, 180, 270. Note: PDFium's rotation is clockwise; e.g. 90 means rotate the page 90° clockwise from its on-page orientation.

Value

A pdfium_bitmap object - an integer matrix with class = c("pdfium_bitmap", "nativeRaster"), dim = c(height, width), channels = 4L, plus attributes dpi, source_page, rotation_applied.

See also

as.raster.pdfium_bitmap(), as.array.pdfium_bitmap() for output-shape conversions; pdf_page_size() and pdf_page_rotation() for the source page's dimensions.

Examples

fixture <- system.file("extdata", "fixtures", "shapes.pdf",
  package = "pdfium"
)
if (nzchar(fixture)) {
  bmp <- pdf_render_page(pdf_doc_open(fixture), dpi = 96)
  bmp # human summary
  if (interactive()) plot(bmp) # render to the active device
}