Preparing artwork for applique: SVG vs PNG, thin details, tips and holes

An appliqué design is a piece of fabric with a satin border around it. That single fact decides what artwork works: the shape must be cuttable from cloth, placeable by hand, and wide enough everywhere for a 3 to 5 mm satin to sit on it. Most artwork that looks fine as a print fails one of those. This guide walks through what to fix before you upload, and what the tool does on its own.

What traces well

The ideal input is a filled, closed vector shape: an SVG with one or a few paths, no strokes, no gradients, no clipping masks, no text elements. Silhouettes, blocky mascots, hearts, stars, leaves, badges, chunky letters. If you can imagine cutting it from felt with scissors in one go, it will work.

Artwork that needs preparation:

• Line art (an outline with a stroke and no fill). The tool sees a stroked path as a thin ring, not a filled shape. Convert the stroke to a filled path or, better, fill the shape the lines enclose.
• Photos and shaded illustrations. No edge to trace. Reduce to flat colours first, or trace by hand.
• Thin details: whiskers, stems, antennae, serifs, script hairlines. Anything narrower than the satin width disappears (explained below).
• Many small pieces. Every separate island is a separate piece of fabric to cut and place. Five pieces at 20 mm are far harder than one piece at 100 mm.
• Text as a text element. Convert to outlines, or type it in the studio.

The rule that decides everything: feature width versus satin width

The satin border is centred on the outline, half its width inside the fabric and half outside. At the default 4 mm width, 2 mm of satin lands on the fabric from each side of a feature. A feature 4 mm wide is therefore covered edge to edge by satin from both sides; the two satin bands overlap each other and there is no visible fabric between them. That is not appliqué any more, it is a satin stitch, and a poorly built one, because the overlapping columns double the density and the fabric sliver underneath has nowhere to be caught.

The engine handles this by shortening the inner rail on narrow features so the columns do not cross, but the piece itself is still a sliver a cutter cannot cut cleanly and a hand cannot place. The tool flags a minimum feature width in the analysis.

| Satin width | Minimum feature width to stay appliqué | Comfortable feature width | | --- | --- | --- | | 3 mm | 4 mm | 6 mm | | 4 mm | 5 mm | 8 mm | | 5 mm | 6 mm | 10 mm |

The "comfortable" column leaves at least 2 mm of visible fabric between the two satin bands after placement error. Widen thin parts of the artwork, or split the design so the thin part becomes plain stitching added later in your embroidery software.

Sharp tips

A pointed tip (a star's point, a heart's bottom, a leaf's end) is where appliqué fails first, and the reason is geometric. On a straight edge, the satin's inner end sits 2 mm inside the fabric outline for a 4 mm satin. At a tip, the two edges converge, so the inner ends of the columns from either side run into each other and the satin has less fabric to bite into. The engine fans the columns at sharp convex corners (it rotates them toward the bisector so the inner ends stay deep) and shortens the stitches, but a tip sharper than about 30 degrees still leaves the inner end close to the fabric edge.

The consequence shows up in the cut allowance. The balanced allowance is roughly (half the satin width plus 0.8 mm of bite minus the depth of the satin's inner end inside the fabric) divided by two. Along a straight edge that depth is 2 mm and the balanced allowance is 0.4 mm. At a tip the depth drops, the allowance the tip needs rises, and since one allowance is used for the whole shape, the tip drags the pass rate down. The cut allowance guide has the calculator.

Fix: blunt the tip. Round it with a radius of 2 to 3 mm, or cut it flat. At 100 mm the eye does not notice a 2 mm radius on a star point, and the satin at the tip becomes a proper fanned corner instead of a pile of overlapping columns.

Holes and counters

Letters like A, B, D, O, P, Q, R and shapes like a donut or a wreath have holes (typographers call the enclosed ones counters). There are two ways to build them, and the tool supports both:

Hole with satin. The outline includes the hole. The placement run stitches the outer outline and the hole outline; the tack-down does the same, inset 1.2 mm on both; the cut file cuts the hole out of the piece; the satin borders both. The hole must be large enough to be a real hole after two satin bands eat into it: for a 4 mm satin, at least 8 mm across, and comfortably 12 mm. Under that, the satin fills it.

Two pieces of fabric. Fill the hole in the artwork so the letter becomes a solid blob, and add the counter back as a second piece in the base fabric colour on top, or leave it solid. Brother's PE-Design calls the first approach "hole sewing" and treats it as a setting to switch on for A, B, O; the point is that it is a choice, not an automatic outcome.

Our default is the hole with satin when the hole is wide enough, and a warning when it is not. For monograms the letters and monograms guide covers which bundled fonts keep their counters open at 25 mm cap height.

Line art needs closing

Traced artwork and hand-drawn SVGs often have gaps: a stroke that stops 0.5 mm short of the next one, an outline that never joins. To an embroidery engine a gap means the shape is not closed, and an unclosed shape has no inside to fill and no outline to border. The PNG importer has an auto-close step for small gaps in a traced mask, but for vector input it is your job. In Inkscape: select the path, Path, then Object to Path if needed, then check for open subpaths in the node editor; Path, then Union to merge overlapping pieces into one filled outline.

The same applies to overlapping objects: a mascot drawn as a head circle on a body ellipse is two paths. Union them so the outline is the silhouette, not two shapes stacked with a seam.

Text should be outlined

An SVG text element carries a font name, not letter shapes. If the machine, browser or tool does not have that font, the text is substituted, and the substitute is usually a thin default that fails the feature-width rule. Convert text to outlines in your design program (Illustrator: Create Outlines; Inkscape: Object to Path; Affinity: Convert to Curves) before exporting.

Better, do not bring text in as artwork at all. The studio has 17 open-licensed fonts selected for heavy strokes and few thin joins, sets a minimum 25 mm cap height, and merges script letters into one piece. See the appliqué font generator and the letters guide.

PNG import: what happens to a bitmap

A PNG has no shapes, only pixels, so the importer has to invent an outline. Here is what it does, in order, so you can prepare the file to suit it.

1. Background removal. If the image has transparency, the transparent pixels are the background. If it is opaque, the four corner colours are averaged, and pixels close to that colour and connected to the border are flood-filled as background. So: export with a transparent background, or make sure the background is one flat colour that reaches all four corners and the subject does not touch the edge.
2. Threshold. When a background was found, everything that is not background is the shape. When no background was found (a black drawing on white, or a photo), the image is reduced to luminance and split at an automatic threshold (Otsu's method, which picks the split that best separates the two brightness groups); dark becomes the shape. There is an invert switch for white-on-dark art, and a manual threshold slider.
3. Colour separation. Ask for two or more pieces, and the foreground pixels are clustered by colour (k-means) into that many groups; each group becomes its own piece with its own fabric. A three-colour mascot becomes three pieces stacked in stitching order.
4. Trace and clean. The mask is traced to a polygon, speckles below a size threshold are dropped, small gaps are closed, and the result goes through the same geometry as an SVG.

Physical size comes from a DPI hint in the file if there is one (PNG pHYs, JPEG JFIF/EXIF); otherwise you set the width in millimetres. Always check the size before exporting; a 300 dpi scan of a 4-inch drawing and a 72 dpi screenshot of the same drawing produce very different millimetres.

Size: 80 mm and up

The errors in an appliqué stitch-out are absolute, not relative. A cutter is off by about 0.25 mm and a hand by about 0.5 mm whether the piece is 40 mm or 140 mm wide. The satin's tolerance window (about 3 mm for a 4 mm satin) is also absolute. What changes with size is the geometry: smaller pieces have proportionally more tips, tighter curves, narrower features and smaller holes, and each of those eats into the window. Our model shows the pass rate dropping below 80 mm for typical shapes, and the same heart that passes at 92 percent at 100 mm is borderline at 60 mm.

Practical minimums, common practice among appliqué digitizers and consistent with our model:

If the design must be small, go to a 3 mm satin only if placement is careful, or accept that the small parts become plain satin rather than appliqué. The resize guide explains why scaling a finished appliqué file does not fix any of this, and the stitch types guide covers what changes when the border is not satin.

A checklist before upload

• One closed, filled path per fabric piece; strokes converted to fills; text converted to outlines.
• No feature narrower than 5 mm at a 4 mm satin; blunt every tip to a 2 mm radius or more.
• Holes at least 8 mm across, or filled.
• Overlapping objects unioned into a silhouette.
• Design at least 80 mm on its long side; check which hoop it fits.
• PNG: transparent or flat single-colour background touching all four corners, subject not touching the edge, at least 1,000 pixels across.