Annotate Existing Text

Add an Underline or StrikeOut annotation to text already present in an unrotated PDF by extracting its text-showing operations, converting the PDF bottom-left origin to Recipe's top-left coordinates, then editing the page.

This example marks every text operation that reads exactly Draft. Matching uses the decoded text, so non-ASCII words work too. width must describe the known visual bounds in the source template; use a separate region for each different width.

import { createMuhammaraWasm, createRecipe } from "@muhammara/wasm";

var muhammara = await createMuhammaraWasm();
var Recipe = await createRecipe();
var inputBytes = new Uint8Array(await inputFile.arrayBuffer());
var reader = await muhammara.createReaderAsync(inputFile);
var pageNumber = 1; // Recipe pages are one-based.
var pageIndex = pageNumber - 1; // Reader pages are zero-based.
var matches;

try {
  matches = reader.extractPageText(pageIndex).filter(function (element) {
    return element.text === "Draft";
  });
} finally {
  reader.end();
}

var pdf = new Recipe(inputBytes);
var page = pdf.pageInfo(pageNumber);

pdf.editPage(pageNumber);
matches.forEach(function (match) {
  pdf.annot(
    match.textMatrix[4],
    page.height - match.textMatrix[5] - match.fontSize,
    Recipe.AnnotSubtype.UNDERLINE,
    {
      width: 28,
      height: match.fontSize,
      color: "#008000",
      text: "Reviewed",
    },
  );
});
var outputBytes = pdf.endPage().endPDF();

Use Recipe.AnnotSubtype.STRIKE_OUT instead to create strikeout annotations. The reader's textMatrix uses PDF's bottom-left coordinates, while Recipe uses a top-left origin; the page.height - y - fontSize conversion above applies to unrotated pages only.

extractPageText() reports a text operation's decoded text, raw content, origin, font resource, and font size. It does not calculate glyph bounds, so it cannot accurately derive width for arbitrary PDFs. This pattern is appropriate for a controlled template where the target text and its bounds are known. For arbitrary documents, obtain glyph bounds from another layout or text-analysis tool before creating the annotation. See Find Text Positions In A PDF for the extractor's complete limitations, and Add Review Annotations for annotation options.