Free Halftone Generator & Print Prep Tool
Convert any artwork into halftones, knock out backgrounds, and generate white underbases for DTF transfers and screen printing. Preview your design on t-shirts, hoodies and totes in 20+ colours. No software, no signup.
How to use it → What every setting means →
Your Artwork
Source
Output
Zoomed in? Drag either preview to pan. Both panes stay in step so you can compare the same spot.
On garment
—How to use this tool
The whole job takes about two minutes. Here's the path most people follow, then what every single setting actually means.
- 1
Upload your artwork
Drop in a PNG or JPG. A transparent PNG is ideal — if your file already has a transparent background you can skip the knockout step entirely. Nothing is uploaded to a server; the file is read straight into your browser.
Size matters more than you'd think. Aim for at least 300 pixels for every inch you'll print. A 12″-wide front print wants a file around 3600px wide. A 600px logo blown up to 12″ will halftone into mush no matter what you do here.
- 2
Pick your print method
The five presets set roughly a dozen values at once — frequency, angle, dot shape, dot gain, dot limits and screening type — to sensible starting points for that method. Pick the one that matches how the job will actually be printed and you can ignore most of the advanced controls.
- Screen · standard — 156–200 mesh with plastisol. The default for most apparel work.
- Screen · fine detail — 230–280 mesh, finer dots, more detail held.
- Index / no moiré — switches to stochastic square dots. Use when you're fighting moiré or printing index-style on dark garments.
- DTF transfer — much lower dot gain and a finer screen, because there's no mesh and no squeegee pressure.
- Vintage / retro — big, deliberately visible dots for that worn band-tee look.
- 3
Fix the contrast before you screen it
This is the step people skip, and it's the one that decides whether your halftone looks good. A normal photo has most of its tones bunched in the middle, so screening it straight gives you a field of near-identical mid-sized dots — grey mush with no punch.
Hit Auto levels first. It stretches the tonal range so your lightest areas become clean fabric and your darkest become solid ink. Then look at the histogram: you want the bars spread across the full width, not huddled in the centre. Nudge the black and white points in by hand if auto was too timid or too aggressive.
Reading the histogram: left is shadows, right is highlights. The amber shaded bands at each end are the tones your press physically can't hold — anything in the right band is too light to print, anything in the left band will flood to solid. A little in each band is normal; a lot means you're losing detail.
- 4
Set the screen to match your mesh
If you're screen printing, type your mesh count into the mesh box and click Apply. The tool picks a frequency in the right range and deliberately avoids ratios that land on a whole number, because an integer mesh-to-LPI ratio lines the dot grid up with the thread grid and makes moiré much more visible.
If you're doing DTF, mesh is irrelevant — just leave the preset alone. Halftoning for DTF isn't about what a screen can hold; it's about laying down less ink so the print feels softer, or getting a genuine vintage screen-print look.
- 5
Knock out the background if it has one
Switch to the Knock out background tab, click Pick from image, then click the background in the source preview. Raise the tolerance until the background is fully gone, and add a pixel or two of edge softness to clean up the fringe.
On DTF this isn't optional. Leave a white background in place and it prints as a visible white rectangle around your design on a coloured garment.
- 6
Generate a white underbase for dark garments
On anything darker than a pale grey, colours need a white layer underneath or they go muddy. Switch to the White underbase tab and it builds one from your artwork. Leave the choke at 3px and Protect thin lines switched on unless you have a specific reason not to.
Skip this entirely for white or very light garments — you'd just be adding cost and stiffness for nothing.
- 7
Check it on the actual garment colour
Pick the garment, the print position and the size. The readout tells you the finished print dimensions in inches at 300 DPI, so you can catch a design that's too small to fill the space before you order anything.
Then open Compare on multiple colours. Your knockout can look perfect on white and show an obvious fringe on black — this is the fastest way to spot it.
- 8
Download what you need
- PNG — full original resolution, transparent background. Fine for DTF and for most film output.
- SVG — every dot as a real vector shape. Better for screen film, because it rasterises at your output device's native resolution instead of ours. Opens in Illustrator, Affinity or Inkscape.
- Underbase PNG — the white layer as its own file, ready to sit under your colour layer.
Do this once, then everything else is accurate
Under Advanced controls there's a calibration wedge. Download it, print it on the press, ink and garment you actually use, and look at the result. The lightest patch still showing dots is your real minimum dot. The darkest patch still distinguishable from solid is your real maximum. And if the patch labelled 40% comes out looking more like 58%, that 18-point gap is your dot gain.
Put those three numbers into the Advanced settings and every separation you make afterwards is calibrated to your specific setup rather than to an industry average. It takes one screen and about ten minutes, and it's the difference between guessing and knowing.
Every setting, explained
What each control does, what to set it to, and how to tell when it's wrong.
Tonal prep
Auto levels
What it does: Finds the darkest and lightest tones actually present in your image and stretches them to fill the full range from solid ink to bare fabric.
Set it to: Just press it, first, every time. It runs automatically on upload too.
When it's wrong: On artwork that's deliberately low-contrast or has a large flat background, auto can over-stretch and blow out detail. If the result looks harsh, press it and then walk the black and white points back a little by hand.
Black point
What it does: Sets the brightness below which everything becomes solid ink. Raising it makes shadows deeper and more solid.
Set it to: Just below where the histogram data starts on the left. If there's a flat gap before the bars begin, you're wasting range.
When it's wrong: Too high and your shadows turn into one featureless black blob with no detail. Too low and dark areas look washed out and grey.
White point
What it does: Sets the brightness above which everything becomes bare fabric — no ink at all.
Set it to: Just above where the histogram data ends on the right. Bringing it down cleans up dull greyish highlights that would otherwise print as a haze of tiny dots.
When it's wrong: Too low and you lose highlight detail — faces go flat, clouds vanish. Too high and your whites are dirty.
Midtones (gamma)
What it does: Bends the tones between black and white without moving either end. Above 1.00 opens the midtones up (lighter, more shadow detail); below 1.00 pushes them down for a punchier, more graphic result.
Set it to: Leave at 1.00 to start. Drop to around 0.80 for a bold, high-contrast look; lift to 1.20 if faces or detail are disappearing into shadow.
When it's wrong: Too low and the image goes heavy and closed-up. Too high and it looks washed out and flat.
Invert
What it does: Flips light and dark, so what was highlight becomes ink and vice versa.
Set it to: On when you're printing a light ink onto a dark garment — white ink on black, for instance. Off for the usual dark-ink-on-light-fabric case.
When it's wrong: If your preview looks like a photographic negative, you've got it on when you didn't want it.
The screen
Frequency (LPI)
What it does: Lines per inch — how many rows of dots fit into an inch. Higher means smaller, tighter dots and more detail; lower means bigger, more visible dots.
Set it to: Your mesh count divided by about 4 to 5, or use the mesh box to have it worked out for you. For DTF, 45–65 is a good range. For a deliberate retro look, drop to 25–35.
When it's wrong: Too high for your mesh and the dots won't hold — fine detail disappears on exposure and the print looks patchy. Too low and you see the dot pattern instead of the image.
Mesh count box
What it does: You enter the mesh count of the screen you'll burn; it recommends a frequency and warns you if your current one is risky.
Set it to: Whatever's written on your frame. Then click Apply.
Why it doesn't just divide by 4: The mesh-to-frequency ratio shouldn't land on a whole number. At exactly 4:1 or 5:1 the dot grid lines up with the thread grid and moiré becomes much more visible, so the tool picks a frequency whose ratio sits between whole numbers.
Dot shape
What it does: The shape each dot is drawn as. It changes both how tones transition and the character of the print.
Set it to: Elliptical for most screen printing — it's the default for a reason. Round for a classic look. Square for maximum sharpness and index-style work. Diamond, crosshatch and line are aesthetic choices — geometric, pen-and-ink and engraving respectively.
Why elliptical wins: Round dots all touch their neighbours at the same moment around 50%, so there's a visible jump in tone right through the midtones. Ellipses join along their narrow axis first and then the long one, so the transition is gradual — smoother gradients in skin tones and skies.
Ink colour
What it does: Changes the colour the dots are drawn in, for both the preview and the exported file.
Set it to: The actual ink you'll print with, so the garment mockup tells you the truth. This is a single-colour spot halftone — one screen, one ink.
Advanced — screening & angle
Screening type: AM vs FM
What it does: AM puts dots on a fixed grid at a set angle and varies their size with tone — the classic halftone. FM (stochastic) keeps every dot the same size and varies how densely they're scattered.
Set it to: AM for smooth gradients and photographic work. FM when you're fighting moiré, printing on textured fabric, or working index-style with opaque inks on dark garments.
The trade-off: FM has no grid and no angle, so it physically cannot moiré — that's why index separations use it. The cost is a slightly grainier look up close.
Angle
What it does: Rotates the whole dot grid. Only applies to AM screening — FM has no angle, so the control greys out.
Set it to: 22.5°, and leave it there. Including on multi-colour jobs.
The thing that catches people out: For garment printing you use the same 22.5° on every colour of a job. The familiar 15°/45°/75° rosette set is for CMYK on paper, where there's no woven mesh with an angle of its own to conflict with. Applying litho angles to screen printing is a common and expensive mistake. At 0°, 45° and 90° the grid aligns with the mesh threads and you get moiré or dropped dots.
Tone range
What it does: Shifts overall ink coverage up or down after the levels have been applied. A blunt global lighten/darken.
Set it to: 50% — it's a nudge control, not a primary one. Fix contrast with the levels instead; they give you far more control.
Advanced — press compensation
Dot gain
What it does: Ink spreads when it hits fabric, so every dot prints bigger than it was on the film — a 40% dot can press as 58%. This setting shrinks your midtones in advance by the amount you expect to gain, so the pressed result lands where you wanted it.
Set it to: 20–30% for plastisol on cotton. Around 5% for DTF, where there's no mesh and no squeegee pressure. 0 if your RIP already applies its own compensation curve — otherwise you'll be correcting twice and the print will come out too light.
When it's wrong: Too low and your print comes out dark and muddy with the midtones filled in. Too high and it comes out weak and washed out.
Note: the correction is strongest in the midtones and tapers to nothing at both ends, because that's where gain actually happens — dots have the most edge relative to their area around 50%.
Min dot
What it does: Drops any dot smaller than this to nothing. Below roughly 5% a dot won't survive screen exposure — it washes out when you rinse the emulsion and prints as nothing anyway.
Set it to: 8% for typical screen work, 3–5% if you have a good exposure unit and fine mesh, 2% for DTF where there's no exposure step at all.
When it's wrong: Too low and you get speckly, unreliable highlights that vary between prints. Too high and highlight detail falls off a cliff — watch the warning panel, it tells you how much you're losing.
Max dot
What it does: Snaps anything above this to solid. Past roughly 85% dots merge together on press and the shadow detail you thought you had is gone regardless.
Set it to: 85% for screen printing, up to 95%+ for DTF.
When it's wrong: Set too high, the preview shows shadow detail that won't survive the press — you're lying to yourself. Set too low, dark areas go flat and lose depth.
Calibration wedge
What it does: Generates a printable test strip of 14 known tint values from 5% to 100%, at your current settings, at true 300 DPI, with those settings stamped on the sheet.
Set it to: Not a setting — a one-off job. Print it on your real press, ink and garment, then read your true min dot, max dot and dot gain off the result and enter them above.
Worth knowing: the wedge deliberately does not apply dot gain compensation. It shows the true requested values so you can measure the gap.
Background knockout
Pick from image (eyedropper)
What it does: Samples the colour you click on in the source preview and marks it for removal.
Set it to: Click somewhere in the middle of the background, away from any edges, where the colour is purest.
Tolerance
What it does: How similar a pixel has to be to your picked colour before it gets removed.
Set it to: Start at 30 and raise it until the background is fully gone. JPEGs need more than PNGs, because compression leaves the background slightly uneven.
When it's wrong: Too low and you get patchy leftovers or a coloured halo around the design. Too high and it starts eating parts of your artwork that happen to be a similar colour.
Edge softness
What it does: Feathers the cut-out edge so it doesn't look like it was cut with scissors.
Set it to: 2px for most things. 0 for hard-edged vector-style artwork. 3–4px for photographic subjects with hair or fur.
When it's wrong: Too little and edges look jagged and hard. Too much and the design goes soft and starts to look like it's fading out.
White underbase
Choke
What it does: Shrinks the white layer inward from the edges so the colour printed on top completely covers it.
Set it to: 3px. That's the common industry default, and most providers sit between 2 and 5.
When it's wrong: Too little and a sliver of white peeks out around your design — the dreaded halo — as soon as registration drifts slightly. Too much and the colour edges lose their white backing and go dull, and past about 5px it starts reading as a visible outline. If you need more than 5px, the real problem is press registration, not this slider.
Protect thin lines
What it does: Applies the full choke to large shapes but backs off automatically on thin ones.
Set it to: On, essentially always.
Why it exists: A choke works inward from every edge. On a big solid shape that's fine. On 4px-wide text a 3px choke removes the underbase completely — the letters then print with no white behind them and effectively vanish on a dark garment. With this on, the tool measures how thick each part of your artwork is and keeps a spine of white running down the centre of anything too thin to survive, while still choking broad areas fully.
White density
What it does: Variable lays more white under bright, saturated colours and less under dark ones. Flat 100% lays full white everywhere.
Set it to: Variable to save ink and get a softer hand. Flat if you want maximum consistency, or you're printing on a garment colour you haven't tested.
Why it matters: White is the most expensive ink in DTF and the thickest layer on the garment. A pale yellow doesn't need the same backing as a saturated red to read on black. Shops genuinely differ on this — if yours has a house standard, follow it.
No white under blacks
What it does: Removes the underbase entirely beneath near-black areas of your artwork.
Set it to: On for designs with large black areas printing on dark garments — it can cut white usage noticeably. Off if you print on light garments, where black artwork still needs backing to read properly.
Worth knowing: this one is genuinely contested. Some shops swear by knocking white out under blacks to save ink; others lay full white under everything for consistency. It's off by default so you opt in deliberately.
Mockup & exports
Garment, position and print size
What they do: Place your design on a t-shirt, hoodie or tote at centre chest, left chest or full front, at a size you control.
Watch the readout: it shows the finished print dimensions in inches at 300 DPI. If a full-front print is coming out at 4″ wide, your source file is too small for the placement you've chosen.
Compare on multiple colours
What it does: Renders your current output on eight garment colours at once.
Why bother: a knockout that looks flawless on white can show an obvious dark fringe on black, and an underbase halo only ever shows up on dark fabric. One glance here catches both.
PNG vs SVG export
PNG is a pixel image at your file's full original resolution with a transparent background. Right for DTF, and fine for most film output.
SVG makes every dot a real vector shape. Better for screen film, because it rasterises at your output device's native resolution rather than being locked to ours — crisper dot edges, cleaner exposure, better dot holding. It also opens straight into Illustrator, Affinity or Inkscape if you want to edit before output.
Heads up: at high frequencies on a large file the SVG can contain hundreds of thousands of shapes and take a moment to build. If it struggles, drop the frequency.
Three print-prep tasks, one tool
Built specifically for screen printing and DTF transfer workflows. No Photoshop or Illustrator needed.
Halftone conversion
Convert continuous tones to a printable dot grid. Adjust LPI, angle and dot shape to match your screen mesh or DTF preference. Six dot shapes covering moiré-resistant round through pen-and-ink crosshatch.
Background knockout
Eyedropper-based removal with tolerance and edge softness. Critical for DTF — without it you get a visible white rectangle around your design when pressed onto coloured fabric.
White underbase
Generates the white ink layer that makes colours pop on dark fabric. Choke control shrinks the white slightly so it doesn't peek past your colour edges.
How it compares
| Feature | Brandum (this tool) | Separation Studio NXT | Generic halftone apps |
|---|---|---|---|
| Price | Free | £200+ / year | Free with signup / watermark |
| Works in browser | ✓ | ✗ (desktop install) | ✓ |
| Privacy (no upload) | ✓ | n/a | ✗ Usually uploaded to cloud |
| LPI / angle / dot shape control | ✓ Full | ✓ Full | Basic only |
| Background knockout | ✓ | ✓ | Often missing |
| White underbase + choke | ✓ | ✓ | ✗ |
| Garment mockup preview | ✓ 3 garments × 20 colours | Basic shirt preview | ✗ |
| Multi-colour comparison | ✓ | ✗ | ✗ |
| Dot gain compensation | ✓ | ✓ | ✗ |
| Min / max dot limits | ✓ | ✓ | ✗ |
| AM + FM (stochastic) screening | ✓ | ✓ | AM only |
| Calibration wedge generator | ✓ | ✗ | ✗ |
| Tonal range warnings | ✓ | ✗ | ✗ |
| Levels + histogram before screening | ✓ | Via Photoshop | Contrast slider only |
| Thin-line-safe adaptive choke | ✓ | ✓ | ✗ |
| Variable white density | ✓ | ✓ | ✗ |
| Mesh → LPI moiré calculator | ✓ | ✗ | ✗ |
| SVG vector export | ✓ free | ✓ | Paid upgrade |
| Full-resolution export | ✓ free | ✓ | Often capped / watermarked |
| Photoshop required | No | No | No |
LPI & mesh count reference
Quick reference for matching halftone frequency to your screen mesh count.
| Mesh count | Recommended LPI | Best for |
|---|---|---|
| 110–156 | 30–35 | Simple spot colour with tints, bold designs |
| 180–200 | 40–45 | Standard apparel printing — most jobs |
| 230–280 | 50–55 | Detailed art, fine halftones, photorealistic |
| 305+ | 55–65 | High-detail simulated process, fine line work |
| DTF (no mesh) | 45–65 | For ink reduction & softer hand feel |
Frequently asked questions
What's the difference between halftone for DTF and for screen printing?
For screen printing, halftones are essential because the screen mesh can only print ink or no-ink — there's no in-between. Dots of varying sizes trick the eye into seeing shades. For DTF, halftones aren't strictly required (the printer can print gradients), but they reduce ink coverage so the print feels softer on fabric, and they give an authentic vintage screen-print look without paying for an actual screen print.
What LPI should I use?
For screen printing, divide your mesh count by 4 or 4.5 to get the LPI. So 156 mesh = 35-39 LPI. For DTF, 45-55 LPI is a good range for most work. Lower LPI (25-35) gives the chunky retro look; higher LPI (55-65) preserves more detail but uses more ink.
Why is 22.5° the default angle — and what about multi-colour jobs?
At 0°, 45° and 90° the halftone grid lines up with the woven threads of your mesh, so dots land on threads and either disappear or throw a moiré pattern. 22.5° sits half way to 45° and closer to horizontal, which both dodges the mesh and reads cleanly to the eye.
Here's the part that trips people up: for garment printing you use the same 22.5° on every colour, including multi-colour and simulated process work. That's what AccuRIP defaults to and what most production shops run. The familiar 15°/45°/75° rosette set belongs to CMYK litho on paper, where there's no mesh with an angle of its own to fight — applying it to screen printing is a common and expensive mistake. If you genuinely need separated angles, 22.5 / 52.5 / 82.5 is the set to use, but try a single angle first.
What does choke do in the white underbase?
The white underbase needs to be slightly smaller than your coloured top layer — otherwise tiny printing misregistrations cause the white to "peek out" around the edges (a "halo"). Choke shrinks the underbase by 1-5 pixels. 2px is safe for most jobs. If your printer has tight registration, use less; if not, more.
Why does my knocked-out PNG have a coloured fringe?
If the original image had a coloured background blended into the design edges (e.g. a JPEG with white background where the foreground is anti-aliased), you'll get fringe pixels that aren't quite white but aren't quite the design colour either. Increase the tolerance to grab more of those edge pixels, then add edge softness to feather what remains. For best results, design with transparent backgrounds in your original file (PNG, not JPEG).
Can I use this for full-colour CMYK separations?
Not yet — this tool focuses on single-colour halftones, background knockout, and underbase generation. Full CMYK or simulated-process separations (each colour as its own halftone at a specific angle) are more involved. If you need that, send your file to customersupport@brandum.com and we'll prep the seps for you.
Why a t-shirt mockup preview?
Because your knocked-out design looks completely different on white vs black vs navy fabric. The comparison grid lets you see your design on 8 garment colours at once, so you can spot whether the knockout has fringing on certain backgrounds, whether you need an underbase for dark garments, or whether the colour you chose for halftone ink will actually read on the shirt colour you're printing on.
What is dot gain and why does this tool compensate for it?
When ink hits fabric it spreads, so the dot that prints is always bigger than the dot on your film. A 40% dot can press as 58% — that's 18 points of gain, and it's worst in the midtones where dots have the most edge relative to their area. The result is a print that comes out muddy and too dark. This tool pre-shrinks your midtones by the expected gain so the pressed result lands where you actually wanted it. Textile plastisol typically runs 15–25%; DTF is much lower because there's no mesh and no squeegee pressure. Set it to 0 if you're outputting film for a RIP that already applies its own curve.
Why do min and max dot settings matter?
A screen physically cannot hold a dot below about 5% — it washes out when you rinse the emulsion, so those areas print as nothing. At the other end, dots above roughly 85% merge together and flood into a solid, so any shadow detail you thought you had is gone. Generic halftone tools happily render 2% dots and 97% dots that will never survive the press. This tool drops the ones that won't hold and snaps the ones that will fill in, so the preview matches reality. It also warns you when a large share of your artwork falls outside that printable window.
What's the difference between AM and FM screening?
AM (amplitude modulated) is the classic halftone: dots sit on a fixed grid at a set angle, and the dot size varies with tone. FM (frequency modulated, also called stochastic) keeps every dot the same size and varies how densely they're scattered instead. Because FM has no angle and no repeating grid, it physically cannot moiré — which is why index colour separations use it. FM is more forgiving on textured garments and with opaque inks on dark fabric, but it looks slightly grainier close up. Use AM for smooth gradients, FM when you're fighting moiré or printing index-style.
How do I use the calibration wedge?
Download it, output it to film, burn a screen, and print it on the garment and ink you actually use. Then look at the result: the lightest patch that still shows visible dots is your real minimum dot, and the darkest patch that still looks different from solid black is your real maximum. Put those two numbers into the Min dot and Max dot settings. If a patch labelled 40% looks like it printed around 55–60%, that gap is your dot gain — set the dot gain slider to the difference. Do this once per press-and-ink combination and every separation you make afterwards will be accurate.
Why does the tool adjust levels before making the halftone?
Because that's the actual professional workflow, and skipping it is the number one cause of disappointing halftones. Every prepress guide describes the same three steps: convert to greyscale, stretch the tonal range with Levels or Curves, then screen. A normal photograph has most of its tones bunched in the middle, so if you screen it straight you get a field of near-identical mid-sized dots — grey mush with no punch. Pull the black point up, bring the white point down, and suddenly the highlights are clean fabric and the shadows are solid ink with real detail in between. The tool runs Auto levels for you on upload, and the histogram shows you what you've got, with the unprintable ends shaded so you can see how much of your image falls outside what the press can hold.
What does "protect thin lines" do in the underbase?
It stops the choke from destroying fine artwork. A choke works by shrinking the white layer inward from every edge — fine on a big solid shape, disastrous on 4px-wide text, where a 3px choke eats the underbase completely. The letters then print with no white behind them and effectively vanish on a dark garment. With this on, the tool measures how thick each part of your artwork is and keeps a spine of white running down the middle of anything too thin to survive a full choke, while still choking broad areas by the full amount. It's the behaviour proper prepress software has and cheap tools don't.
Why would I want variable white density instead of solid white?
Two reasons: cost and hand-feel. White is the most expensive ink in DTF and the thickest layer on the garment. A pale yellow doesn't need the same backing as a saturated red to read properly on black fabric, and near-black artwork barely needs any at all. Variable density matches the white to what each colour actually needs, which cuts ink use and leaves a softer print. Flat 100% is the safe option if you want absolute consistency, or you're printing on a garment colour you haven't tested. Shops genuinely differ on this — if yours has a house standard, follow it.
Why does the SVG export matter?
A PNG halftone is locked to the resolution it was generated at, so if your imagesetter or film printer outputs at higher resolution than the file, your dot edges are already soft before the screen is even burned. In the SVG every dot is a real vector shape, so it rasterises at whatever resolution your output device runs at — crisp edges, cleaner exposure, better dot holding. It also opens straight into Illustrator, Affinity or Inkscape if you want to edit before output. Most tools charge for vector export; this one doesn't.
Is my image uploaded anywhere?
No. Everything runs in your browser. Your artwork never leaves your device — nothing is saved, logged, or sent to our servers. You can verify this by disconnecting from WiFi after the page loads — the tool will still work normally.
Ready to print it?
You've prepped your file — now let us turn it into shirts, hoodies, totes or transfers. Trade pricing on bulk DTF, gang sheets, and short-run apparel from our East London studio.