PDF to Grayscale / Black & White
Make a colour PDF gray for cheaper printing, black and white, or a night-reading negative.
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About the PDF to Grayscale / Black & White
Turn a colour PDF into shades of gray before you print it. Every colour in the file — text, lines, fills, form fields, comments and pictures — is converted with the formulas the PDF standard defines, so text and drawings stay sharp, selectable and searchable, and the file is truly gray (DeviceGray) rather than colour that only looks gray. Pages with features that can’t be converted exactly, such as colour gradients or spot colours, are redrawn as gray images at the resolution you choose, and the tool lists them.
Two more modes: Black and white turns scanned pages into pure black-and-white images (usually a much smaller file), with an automatic or adjustable threshold and a mode for uneven lighting; Night makes an exact negative — white text on a black page — for reading in the dark. Your file is converted in your browser and never uploaded.
How to use it
- Drop a PDF onto the box above, or tap Choose a PDF to convert. The tool checks every page and tells you which ones (if any) will be redrawn as images.
- Choose Grayscale, Black & white or Night, and look at the preview. For black and white, adjust the threshold or tick Uneven lighting for photos of pages.
- Press Convert PDF, compare Original and Result in the preview, then Download.
Examples
Red headings, blue charts, photos · Grayscale
Headings and charts become gray vector text and lines (red becomes 0.3 and blue 0.11 on the 0–1 gray scale), photos become gray JPEGs; nothing is blurred
Black & white · 300 dpi · Uneven lighting
Pure black text on white paper without the shadows, as 1-bit images that are typically far smaller than colour scans
Night · Invert pictures too
White text on black pages, with every gray value inverted; text stays searchable
Common uses
- Saving colour ink and toner: print gray PDFs on any printer.
- Submitting documents to portals that require black-and-white PDFs, or making scans small enough to upload.
- Checking how a colour design reads without colour (contrast, charts).
- Reading long documents on screen at night with a dark page.
How the colours are converted
Each colour operator in the page — and in form XObjects, patterns, Type 3 glyphs and comment appearances — is rewritten in DeviceGray with the conversions of ISO 32000-1:2008 §10.3:
- RGB:
gray = 0.3 × red + 0.59 × green + 0.11 × blue(§10.3.2) — the luma weights of ITU-R BT.601 (0.299, 0.587, 0.114) rounded to two places. - CMYK:
gray = 1 − min(1, 0.3 × cyan + 0.59 × magenta + 0.11 × yellow + black)(§10.3.3). - ICC-based and calibrated colours are converted as the device colours with the same number of components; indexed colours (palettes) by converting the palette, so the pixels of such images stay exactly as they are.
Pictures are converted too: JPEG photos are decoded and saved again as one-component (gray) JPEGs, other images by their pixel values. Because the result is DeviceGray, printer drivers can print it with black only; colour that merely looks gray may still be printed with colour inks.
Pages redrawn as images
A few PDF features can’t be converted colour by colour without changing how they look: colour gradients (shadings), spot colours (Separation and DeviceN), Lab colours, JPEG 2000 and CMYK JPEG images and images with colour-key transparency. Pages with such content are drawn in your browser, converted to gray pixel by pixel with the same formula, and saved as gray images at the resolution you choose (300 dpi by default). Their text is kept underneath as invisible text, so they stay searchable, and their links and comments are kept. The tool tells you which pages and why before you convert.
Black and white and night reading
Black and white draws each page at 200–400 dpi and turns every pixel black or white. The automatic threshold uses Otsu’s method, which picks the gray level that best separates ink from paper; you can also set it yourself. Uneven lighting compares each pixel with the average of its neighbourhood instead (Bradley’s adaptive method), which removes shadows and gradients from photographed pages. The pages are stored as 1-bit images, and their existing text (for example an OCR layer) is kept as invisible text.
Night converts to gray and inverts every value — the paper becomes black, black text becomes white — and swaps the blend modes that depend on light and dark (Multiply and Screen, Darken and Lighten), so the result is an exact negative.
Limitations
- Pages with colour gradients, spot colours or Lab colours become gray images, so their text is only searchable through the invisible text layer, not editable.
- Black and white makes every page an image; text that wasn’t text before (a scan) stays unsearchable unless it already had an OCR layer — use PDF OCR first.
- Night reading inverts pictures too unless you untick it; untouched pictures can look bright on a black page.
- Password-protected or restricted PDFs must be unlocked first with Unlock PDF.
- Converting changes the file, so existing digital signatures will show as invalid; the tool warns you when a file is signed.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
Will the text stay sharp?
Yes, in Grayscale and Night: text and drawings are converted colour by colour and stay vector text and lines, so they are as sharp as before and still searchable. Only pages with gradients or spot colours are redrawn as images (the tool lists them).
Does converting to grayscale make the PDF smaller?
Usually a little: gray pictures need one channel instead of three. Black & white makes scans much smaller. For a specific size, use Compress PDF to Size.
Why convert instead of choosing “print in grayscale”?
Not every printer or driver offers it, print shops and upload portals often need a gray file, and a converted file prints the same everywhere. It is also a way to check how the document looks without colour.
Is my PDF uploaded?
No. The PDF is opened, converted and saved in your browser; nothing is sent to a server.