Extract an embedded image to a file, picking a sensible format

Convenience helper over pdf_image_filters(), pdf_image_data(), and pdf_image_bitmap(). Inspects the image's filter chain and picks an on-disk format:

Usage

pdf_image_extract(obj, path)

Arguments

obj

A pdfium_obj of type "image".

path

Output file path. If the extension is supplied it's ignored — the function appends .jpg, .jp2, or .png according to the chosen format and returns the actual path used.

Value

Invisibly returns the path written, with the chosen extension applied. The output format can be retrieved by inspecting the file extension on the returned string.

Details

• DCTDecode → write the raw embedded bytes as .jpg.

• JPXDecode → write the raw embedded bytes as .jp2.

• CCITTFaxDecode / JBIG2Decode / RunLengthDecode / FlateDecode / LZWDecode / ASCII85Decode / ASCIIHexDecode chains, or no filter → rasterize via pdf_image_bitmap() and write as a PNG using png::writePNG(). PNG round-trips the alpha channel when present.

Mirrors pypdfium2's PdfImage.extract() convenience.

See also

pdf_image_data() to get the raw bytes directly, pdf_image_bitmap() for the decoded pixel matrix.

Examples

fixture <- system.file("extdata", "fixtures", "image.pdf",
  package = "pdfium"
)
if (nzchar(fixture)) {
  doc <- pdf_doc_open(fixture)
  page <- pdf_page_load(doc, 1L)
  imgs <- Filter(function(o) o$type == "image", pdf_page_objects(page))
  if (length(imgs) > 0L) {
    # The extension is chosen from the filter chain; pass a stem.
    out <- pdf_image_extract(imgs[[1L]], tempfile())
    basename(out)
  }
  pdf_page_close(page)
  pdf_doc_close(doc)
}