Free DTF Knockout & Halftone Generator

What is DTF knockout?

DTF knockout is the technique of removing the background color from a design before printing it as a Direct-to-Film transfer. The most common variants are white knockout (remove white underbase for dark garments), black knockout (remove black for light garments), and color knockout (remove any solid background color).

The result: the shirt color shows through the knocked-out areas, your design uses up to 40% less ink, the print feels softer and more breathable, and it's less prone to cracking after washes.

White knockout — for dark fabric

When your DTF transfer prints on a black, navy, or any dark garment, the printer normally lays a white ink layer (the underbase) under your colors so they appear vibrant. White knockout removes pure white pixels from your design so the underbase isn't printed there — the dark fabric becomes part of your artwork.

Use this for: distressed designs, retro halftones, intentional negative space, and anywhere you want the garment to "show through".

Black knockout — for light fabric

On white, cream, or pastel garments, dark or black areas in a design can feel heavy and stiff. Black knockout removes those areas so the light fabric color fills them naturally. Combined with halftone dot patterns, this is the technique behind most "vintage tee" looks — lighter feel, faster dry, same visual impact.

Color knockout — remove any solid background

If your source PNG has a solid blue, green, or any uniform color background that shouldn't print, the color knockout option samples that exact pixel value and turns it transparent. Adjust tolerance to handle slight color variations, and edge softness for clean anti-aliased edges — especially important for high-DPI DTF output.

Halftone for DTF — what LPI and angle to use

A halftone converts continuous tone into a grid of dots, so the printer lays down less ink while the eye still reads a smooth gradient. On DTF that matters twice over: less ink means a softer hand, faster curing, and far less cracking after washes.

The single most common mistake is running the screen too fine. Transfer film and adhesive powder both spread the dot slightly, so a screen that looks perfect on your monitor closes up into a solid patch on fabric. Start coarse and work finer only if your printer proves it can hold the dot.

• 25–30 LPI — safe on any DTF setup. Visible dot texture, very forgiving. This is where to start.
• 35–45 LPI — needs a well-calibrated printer and good film. Smoother result, less margin for error.
• 55 LPI and above — generally fills in on DTF. This is screen-printing territory, not transfer territory.
• Angle: 22.5° for a single colour — it is the least visible to the eye. If you stack colours, keep each screen at least 30° apart.
• Resolution: set the halftone at your final 300 DPI output size. Scaling a halftone after the fact destroys the dot grid.

Halftone dot shapes: round, ellipse, diamond, square and line

Dot shape changes how tones join up as they grow. It is a smaller decision than LPI, but it is what separates a halftone that looks intentional from one that looks like a printing fault.

• Round — the default, and the most forgiving on DTF. Dots stay separate longest before they merge, so shadows clog last.
• Ellipse — joins gradually along one axis, which reads smoother on skin tones and soft gradients. Clogs earlier in the shadows than round.
• Diamond — crisp, graphic, slightly retro. Good for bold illustration, poor for photographic detail.
• Square — hard-edged and strongest at midtones. Jumps abruptly from open to solid, so use it deliberately.
• Line — not really a dot at all. Gives an engraved or comic-book texture and works well over flat colour fields.

Why halftones fill in, and how to fix moiré

Two different failures get blamed on the same thing. Filling in is the dots merging into solid ink — that is an LPI problem, and the fix is a coarser screen or lifting the gamma so the shadows carry less tone. Moiré is a rippling interference pattern, and it has nothing to do with LPI: your halftone grid is beating against a pattern already present in the source image.

Moiré almost always means the source was already printed — a scan of a poster, a screenshot of a printed catalogue, or a heavily compressed JPEG whose blocking has become a pattern of its own. Work through it in this order:

• Change the screen angle. Switching between 22.5° and 45° resolves most cases on its own.
• Blur the source 0.5–1px first. Counter-intuitive, but it removes the competing pattern without visibly softening the halftone.
• Descreen a scan before halftoning it, rather than halftoning a screen that already exists.
• Lower the LPI last. It works, but it costs you detail, so try the other three first.

Knockout plus halftone: the full DTF prep workflow

Knockout and halftone solve different halves of the same problem, and they belong in a specific order. Knock out first, halftone second — reversing them means you are trying to threshold a background that has already been broken into dots.

• 1. Knock out the background. Pick the colour that should not print. On dark garments that is usually the white underbase; on light garments, the black.
• 2. Check the edges. Semi-transparent rim pixels are what produce a white halo on a dark shirt, because the RIP builds underbase beneath every one of them.
• 3. Set the shirt colour. This flips the ink polarity automatically — on a dark garment the light tones carry ink, on a light garment the dark tones do.
• 4. Apply the halftone. 30 LPI at 22.5°, round dots, then adjust levels until the highlights just start to break up.
• 5. Export a transparent PNG at 300 DPI and drop it straight onto your gang sheet.

If you need genuine channel separations rather than a single-pass halftone — simulated process, spot colours, a dedicated underbase channel — that is a different job. Our color separation Photoshop action handles it, and it works on the same 300 DPI transparent PNG this tool produces.

DTF prep checklist (best practices)

• Resolution: 300 DPI minimum at the print size you'll use. Lower DPI causes pixelation on transfer.
• Format: PNG with transparency. JPEG kills knockout prep because it can't hold transparent pixels.
• Color mode: RGB for DTF (not CMYK). The printer's RIP handles CMYK conversion.
• Choke / spread: If your underbase shows a white halo around the design, ask your DTF service to apply a 2–5 pixel choke on the white layer.
• Edge cleanup: After knockout, zoom to 200% and check for stray pixels around fine details. The "edge softness" slider in this tool handles most cases automatically.
• Test print: Always run one transfer on scrap fabric before doing a full gang sheet.

How it compares

Frequently asked questions

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