How Poly2Path Simplifies Vectorizing Complex Polygons

Optimize SVGs with Poly2Path: Tips, Tricks, and Best PracticesScalable Vector Graphics (SVG) are lightweight, resolution-independent, and ideal for icons, illustrations, and UI elements. Yet complex SVGs — especially those created by designers or exported from vector software — can contain unnecessary or inefficient data that slows rendering, increases file size, and makes animations difficult. Poly2Path is a specialized tool that converts polygon and polyline elements into path elements, enabling cleaner, smaller, and more consistent SVGs that are easier to style and animate.

This article explains why poly-to-path conversion matters, how Poly2Path works, and practical tips, tricks, and best practices for integrating it into your design and development workflow.

Why Convert Polygons/Polylines to Paths?

Uniformity: Paths provide a single, expressive element for describing shapes (lines, curves, complex fills, strokes). Converting polygons/polylines to path ensures all shapes use the same element type, simplifying styling and scripting.
Precision & Control: Paths support cubic and quadratic Bezier curves, precise segment commands, and arc commands, giving more control for smoothing and optimizing shapes.
Better Animations: Path morphing and animations (e.g., stroke-dashoffset, path-based morphing libraries) work best with path data.
File Size & Cleanliness: Properly optimized paths can reduce redundancy, remove unnecessary points, and collapse transforms — reducing filesize compared to verbose polygon data and multiple transforms.
Cross-Tool Compatibility: Some tools and browsers handle paths more reliably than polygon/polylines, especially for complex effects.

How Poly2Path Works (High-Level)

Poly2Path reads polygon and polyline elements and converts their coordinate sequences into equivalent path data (the “d” attribute). The conversion typically follows these steps:

Parse polygon/polyline points into ordered coordinate pairs.
Optionally apply any transform attributes to produce absolute coordinates.
Determine whether to close the path (polygons are closed; polylines are not).
Optionally simplify the points (remove collinear points, merge near-duplicates).
Generate an optimized path string using commands such as M, L, H, V, C, Q, A, and Z where appropriate.
Replace the original element with a element, transferring relevant style attributes (fill, stroke, stroke-width, class, etc.).

Practical Tips and Tricks

1) Preserve Visual Fidelity First

Convert polygons/polylines with transforms applied so you keep the rendered coordinates. Many SVGs rely on transforms to position elements — leaving transforms on the parent while converting may produce visually shifted results.
Use absolute coordinates (capital commands like M and L) in the generated path to avoid unexpected relative-positioning behaviors.

2) Simplify Before Converting (or As Part of Conversion)

Remove redundant points: consecutive duplicate points, or points that lie exactly on a straight line segment, add size without changing the appearance.
Tolerant simplification: use an epsilon distance threshold to remove very close points (e.g., 0.1–0.5 px for most UI icons; higher thresholds for decorative illustrations).
Beware over-simplification: too aggressive simplification alters shape. Test visually and compare rendered output.

3) Handle Closed vs. Open Shapes Correctly

Polygon -> Path should end with Z (closepath) to maintain fill rules and ensure correct rendering.
Polyline -> Path should not include Z (unless explicitly intended) so strokes and open shapes maintain their end caps.

4) Transfer and Normalize Style Attributes

Transfer attributes like fill, stroke, stroke-width, stroke-linecap, stroke-linejoin, fill-rule, opacity, and transform where appropriate.
For maintainability, strip presentation attributes and prefer CSS classes when building a UI system. But if producing standalone SVGs, keep inline attributes that preserve appearance.

5) Optimize Path Commands for Size

Use relative commands where it reduces size (e.g., small repeated segments). However, for converted polygon data that’s already absolute, converting to relative L or l may or may not shrink the string—test both.
Collapse repeated horizontal/vertical segments into H/V commands when coordinates align exactly.
Combine short segments into shorthand cubic/quadratic curves only when it preserves visual fidelity and reduces size.

6) Remove Metadata and Unused Definitions

Strip comments, editor metadata, unused , invisible guides, and empty groups.
Remove unnecessary id attributes unless they’re referenced (e.g., by CSS or ).

7) Round Coordinates Smartly

Round coordinates to a reasonable number of decimal places (commonly 2–3 for icons, 1–2 for large shapes). Rounding reduces filesize and typically isn’t visually noticeable.
Keep higher precision for paths used in animations where subpixel motion matters.

8) Use ViewBox and PreserveAspectRatio Correctly

Ensure the SVG has a proper viewBox. After conversion, update viewBox if transforms or coordinate normalization changed extents.
Prefer viewBox-based scaling over fixed width/height when preparing icons for responsive UI.

9) Match Stroke Rendering Intent

If original polygons used strokes to define shape, converting to path should replicate stroke properties and consider stroke-alignment issues. Note: SVG 2 stroke-alignment support is limited — if stroke alignment matters (inside/outside), convert stroked polygons to filled paths offset appropriately.

10) Test Across Browsers and Tools

Visual diff: render before/after at several sizes and device pixel ratios. Tiny differences can appear at certain scales; tweak rounding/epsilon accordingly.
Test previews in design tools, browsers, and in-app contexts (e.g., inline SVG vs. background-image).

Best Practices for Integrating Poly2Path into Workflows

For Designers

Export simplified SVGs from the design tool (Illustrator/Figma/Sketch) using “Outline stroke” or prepare as paths — then run Poly2Path to normalize any polygons/polylines.
Keep source files (AI/Figma) with editable vectors; perform final conversion/optimization as a build step rather than during authoring.

For Developers / Build Pipelines

Add Poly2Path to your asset pipeline (webpack, gulp, rollup, or CI). Convert during asset compilation rather than runtime.
Combine with other SVG optimizers (SVGO, svg-sprite, svgstore) in the following order:
1. Flatten transforms and convert basic shapes to paths (Poly2Path).
2. Simplify and remove redundant points.
3. Run SVGO with a config that preserves needed attributes (e.g., preserve viewBox, classes).
4. Post-process: minify, sprite, or inline as needed.
Use consistent naming or a manifest so you can retrace optimized icons back to sources.

For Animation/Interaction

For morph animations (e.g., using GreenSock MorphSVG or flubber), ensure paths have matching command structures and similar point counts where possible. Tools such as Shape Shifter or custom interpolation utilities can help.
When preparing for stroke animations, ensure path lengths are preserved and compute stroke-dasharray values reliably.

Examples and Patterns

Simple polygon to path conversion

Original polygon:

<polygon points="0,0 10,0 10,10 0,10" fill="#000"/>

Converted path (closed):

<path d="M0 0L10 0L10 10L0 10Z" fill="#000"/>

Notes:

After conversion you can simplify to use H/V:
```
<path d="M0 0H10V10H0Z" fill="#000"/> 
```
Or round and shorten if appropriate:
```
<path d="M0 0H10V10H0Z" fill="#000"/> 
```

Polyline (open) conversion

Original polyline:

<polyline points="0,0 10,5 20,0" stroke="#000" fill="none"/>

Converted path (open):

<path d="M0 0L10 5L20 0" stroke="#000" fill="none"/>

Common Pitfalls and How to Avoid Them

Losing transforms: Always apply parent transforms during conversion or preserve them explicitly to avoid shifted shapes.
Changing fill rules: Closed path conversion must preserve the original fill-rule (nonzero vs evenodd).
Over-simplification: Blindly removing points can break the design; use conservative defaults and visual checks.
Breaking CSS selectors/IDs: If you remove or rename IDs/classes during optimization, update any CSS/JS that references them.
Unexpected stroke differences: Converting strokes to fills or vice versa can change rendering; keep stroke properties unless intentionally converting to filled geometry.

Tools and Utilities to Combine with Poly2Path

SVGO — powerful SVG optimizer; configure to avoid removing needed attributes.
svgcleaner — alternative for bulk cleaning.
Shape morphing libraries — flubber, GreenSock MorphSVG, Snap.svg — require well-formed paths.
CLI automation — write small scripts (Node.js with cheerio, xmldom) to run Poly2Path and other optimizers in sequence.

Recommended Settings (Starting Points)

Coordinate rounding: 2 decimal places for UI icons; 3–4 for illustrations requiring higher precision.
Simplify epsilon: 0.2 px for icons; 0.5–1.0 px for decorative art (tune visually).
Preserve: viewBox, class, id (unless intentionally removed), fill-rule, stroke attributes used in runtime.
Conversion order in pipeline: flatten transforms → poly2path → simplify points → svgo → sprite/minify.

Summary

Converting polygons and polylines to paths with Poly2Path yields cleaner, more consistent SVGs that are easier to style, animate, and optimize. The key is to maintain visual fidelity while reducing unnecessary data: apply transforms, simplify conservatively, round coordinates smartly, and integrate the conversion into a build pipeline alongside tools like SVGO. Test broadly and preserve attributes your runtime depends on. Properly applied, poly-to-path conversion improves performance, maintainability, and the reliability of SVGs across platforms.