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Per-character fill and stroke colors and text-index mapping

Source: R/text_extras.R
pdf_text_colors.Rd

Returns one row per character on the page with the fill / stroke RGBA colour PDFium reports for that glyph and the text-position the character occupies in the page's extracted text. Suitable for joining onto pdf_text_chars() by char_index.

Usage

pdf_text_colors(page, page_num = 1L)

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.

Value

A tibble with one row per character and columns char_index (1-based), text_index (0-based index in the page's extracted text; NA for generated/hyphen/formatting chars), fill_red, fill_green, fill_blue, fill_alpha, stroke_red, stroke_green, stroke_blue, stroke_alpha (0-255 integers, NA when PDFium reports failure).

Details

Use cases:

  • Detect invisible / clip-mode text (alpha = 0 in fill and stroke) for text-extraction quality checks.

  • Distinguish styled-text passages (e.g. highlights with a non-default fill alpha).

  • Translate between the character-index space PDFium uses internally and the extracted-text index space that pdf_text_search()'s start_char aligns with — characters with text_index = NA are generated / hyphen / formatting chars that don't appear in the rendered text string.

Wraps FPDFText_GetFillColor, FPDFText_GetStrokeColor, and FPDFText_GetTextIndexFromCharIndex.

See also

pdf_text_chars() (per-char geometry / codepoint), pdf_text_render_mode() (per-text-object render mode).