Does thickening change the signature's overall canvas size?

No, the output stays exactly the same width and height as the source. Strokes grow inward toward each other and outward within that same canvas.

How is thickening implemented?

It reuses the same stroke-outline math as the general stroke adder: the shape is dilated outward by the chosen amount on an expanded canvas, then cropped back down to the original dimensions, so newly-thickened pixels are filled with the chosen ink color.

Can very thin strokes disappear if I thicken too much?

Thickening only grows strokes, it never removes them, so a genuinely present (even if faint) stroke will get bolder, not disappear. Extremely large thickness values can eventually merge separate strokes together, though.

What ink color is used for the newly thickened areas?

You choose it; it defaults to a near-black ink color, but you can match it to the signature's existing ink color for a seamless look.

Signature Thickener - Make a Signature's Strokes Bolder

Overview

Introduction

This tool thickens a signature's ink strokes entirely in your browser, making a thin or faint signature read as bolder.

Unlike changing the ink color, this changes the actual shape of the strokes by growing them outward.

What Is Signature Thickener?

A client-side morphological dilation tool: it grows the signature's non-transparent silhouette outward by a chosen number of pixels, filling the newly covered area with a chosen ink color.

The canvas size stays the same as the source; only how much of it is covered by ink increases.

How Signature Thickener Works

There's no dedicated dilation function in this category, but the existing stroke-adder tool already computes exactly that operation: it expands the canvas outward by the chosen amount and fills any newly-added pixel within that distance of an originally-opaque pixel with a solid color.

This tool reuses that stroke-adder result and then crops it back down, centered, to the original width and height, so the net effect is strokes that grow in place rather than a canvas that grows.

When To Use Signature Thickener

Use it on a signature that was signed with a fine-tipped pen and looks too thin or faint when printed or displayed at a different size.

It's also useful for making a signature more legible after scanning at a resolution that thinned out the strokes.

Often used alongside Signature Thinner and Signature Color Changer.

Features

Advantages

Keeps the same canvas dimensions as the source, so it drops directly into place where the original was used.
Reuses proven stroke/crop math instead of a new, untested dilation implementation.
Lets you match the newly added ink color to the existing strokes.

Limitations

Very thick settings can merge separate nearby strokes together, changing the signature's legibility.
It can't recover a stroke that's genuinely absent — only thicken pixels that already have some opacity.

Examples

Bolding a thin signature

Input

A fine-pen signature, thickened by 2 pixels

Output

The same signature with visibly bolder strokes

Each stroke's silhouette grows by 2 pixels in every direction, filled with the chosen ink color.

Matching ink color

Input

A blue-ink signature, thickened with ink color set to the same blue

Output

Thicker strokes that blend seamlessly with the original ink

Setting the fill color to match the existing ink avoids a visible color seam at the newly thickened edges.

Best Practices & Notes

Best Practices

Match the ink color parameter to the signature's actual ink color for a seamless result.
Start with a small amount (1-2 pixels) and increase gradually to avoid merging nearby strokes.

Developer Notes

This is a composition of two existing functions rather than new dilation math: addStrokeToPng (which already dilates an alpha silhouette outward on an expanded canvas) followed by cropPng (to crop back down to the original centered dimensions), avoiding re-deriving a neighborhood search that already exists.

Signature Thickener Use Cases

Bolding a thin or faint signature for better legibility
Compensating for strokes that thinned out during scanning
Making a signature more visible when displayed at a small size

Common Mistakes

Using a thickness so large that separate strokes merge together and the signature becomes harder to read, the opposite of the intended effect.
Leaving the ink color at its default when the signature's actual ink is a different color, creating a visible mismatch.

Tips

Preview the result at the size you'll actually display the signature, since thickening matters most at small sizes.
Use the signature thinner tool afterward if thickening ends up too strong.

Signature Thickener