How to Vectorize for Screen Printing and Textiles
7 min read
Screen printing is a physical process with a hard constraint: each ink is a separate screen, and each screen needs a clean, closed region for the ink to sit inside. A design that resolves into four flat colours is four screens. A design with a gradient is not printable that way at all without halftoning.
Vectorization is how a design that exists only as a raster gets into that shape. This guide covers what to check, and where the automatic result stops and hand work begins.
Separations are colours, and colours are money
Every additional colour is another screen to burn, another pass on the press and another setup charge. So the useful question before converting is not 'how many colours does this image have' but 'how many am I willing to pay for'. Reduce the artwork to that number in a raster editor first — posterise, or select-and-flatten by hand — and convert the reduced version.
Converting the full-colour original and hoping to merge afterwards is the harder route. The tracer will find every distinct region that is actually there, and an image that looks like four colours to the eye often contains forty once compression and anti-aliasing are counted.
Trapping and overprint are still hand work
Screens do not register perfectly. Two adjacent flat colours printed with no overlap will show a sliver of shirt between them wherever the press drifts by a fraction of a millimetre, and it always drifts.
The fix is trapping — deliberately overlapping the shapes slightly so a small misregistration is invisible. No automatic vectorizer does this, and it should not: how much trap and in which direction depends on the press, the mesh and the order of the passes. Expect to add it in Illustrator or your separation software after converting.
DTG and heat transfer have different constraints
Direct-to-garment printing does not have a screen count, so the colour discipline above matters much less — a DTG file can be full-colour. What matters there is edge quality: a vector edge stays crisp when the design is scaled to fit a different garment size, where a raster starts to soften.
Heat transfer vinyl behaves like a cutting job, because it is one: the design is cut from coloured sheet and weeded. Everything in the cutting guide applies — closed contours, few nodes, no features too small to weed.
Check the smallest positive and negative feature
A screen holds ink in the open areas of the mesh. Below a certain size, a positive feature loses definition and a negative one — the counter of an 'e', the gap between two strokes — closes up with ink and disappears. Where that threshold falls depends on the mesh count, but somewhere around half a millimetre at print size is a working rule for a standard mesh.
Look at the traced file at the real print size and specifically at the type. Small serif faces and thin script are where this bites, and the answer is usually to thicken or resize rather than to fight the process.
Step by step
- 01
Decide your colour count first
Each colour is a screen, a pass and a setup charge. Pick the number before converting, not after.
- 02
Reduce the raster to that many flat colours
Posterise or flatten by hand in an image editor. Converting the full-colour original produces far more regions than the design appears to have.
- 03
Convert to SVG
Upload the reduced artwork. The result is an SVG; if your shop asks for EPS by name, save one from that SVG in your editor.
- 04
Add trapping by hand
Overlap adjacent colours slightly so a small misregistration on press does not show the garment between them. This depends on the press and cannot be automated.
- 05
Check the smallest features at print size
Thin strokes and small counters close up on a screen. Thicken or enlarge anything under roughly half a millimetre.
Common problems
- The trace produced far more colours than the design has
- JPEG compression and anti-aliasing created intermediate shades the eye merges but the tracer does not. Posterise the raster to your intended colour count before converting.
- A sliver of shirt shows between two colours on press
- No trapping. Overlap the adjacent shapes slightly in your editor — this is a press-specific decision no converter can make for you.
- Fine type filled in with ink
- The counters are below what the mesh can hold. Enlarge the type or use a heavier weight; this is a limit of the process, not of the file.
- The design has a white box behind it
- The source was a JPEG, which has no transparency, so its white background became a shape. Delete it, and start from a transparent PNG next time.
Frequently asked questions
- What file format do screen printers want?
- Most now take SVG or a PDF made from one. Some older shops still ask for EPS by name — that is the same paths in an older container, and any editor saves one from the SVG in a single step.
- Can vectorization do the colour separations for me?
- It produces flat regions grouped by colour, which is the raw material for separations. It does not produce press-ready separations: trapping, underbase and halftone decisions are press-specific and are added afterwards.
- How many colours can a screen-printed design have?
- Technically as many as the press has stations — commonly six or eight. Economically, each one adds a setup charge, so most commercial work sits at one to four.
- Does this work for embroidery?
- Partly. A clean vector with closed shapes is a much better starting point for a digitiser than a raster, but embroidery needs a stitch file (DST, PES) produced by digitising software, and that step is separate from vectorization.
Related guides
- How to Vectorize for Cricut, Silhouette and Vinyl Cutters — Make cut-ready SVG files: closed contours, no double lines, and shapes a blade can actually follow.
- How to Vectorize a Logo — Rebuild a logo you only have as a small JPG into clean, print-ready curves with exact brand colours.
- How to Vectorize a Flyer or Poster for Large Format — Rescue a flat design for A1 and larger without the soft edges — and know which parts not to convert.