PDF to PNG Red-Tint on macOS in IronPDF for Node.js

Solution

Rasterize to JPG instead of PNG, then use sharp to convert the JPG to a grayscale PNG. This sidesteps the macOS color-channel mapping issue.

Install sharp:

npm install sharp

npm install sharp

Rasterize to JPG, then convert to PNG:

import { PdfDocument, ImageType } from "@ironsoftware/ironpdf";
import sharp from "sharp";

const pdf = await PdfDocument.fromFile("input.pdf");

const [jpgPage] = await pdf.rasterizeToImageBuffers({
    fromPages: 0,
    imageType: ImageType.JPG,
});

const pngBuffer = await sharp(jpgPage)
    .flatten({ background: "#ffffff" })
    .grayscale()
    .threshold(160)
    .png()
    .toBuffer();

Adjust the threshold value between 120 and 200 based on the QR code contrast in your PDF. This post-processing step is safe for QR codes because they are binary: black cells on a white background. A grayscale conversion loses nothing for QR codes.

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