Iurii Visualizes: pi-pi.ee — Live Custom-Colour Preview

The Business Problem

Pi-pi.ee stocks its products in three colours — black, grey, white — and photographs each one. But customers kept asking for colours that aren't on the shelf: a green to blend into a garden, an anthracite to match a façade, a terracotta for a courtyard. Every one of those is a made-to-order paint job, perfectly doable, but invisible on the website. The buyer had to imagine it.

The obvious fix — photograph the product in every offered colour — doesn't scale. Ten colours across several product shots is dozens of new image files to shoot, edit, name, store, and re-do the moment the catalogue changes. And it still only covers a fixed list. The real requirement was different: let the visitor see any offered colour on the actual product, right on the page, without the shop producing a single extra photo.

The Solution

The recolouring happens entirely in the browser, on the photo that's already loaded. Each product photo ships with a transparent-background master. A single SVG duotone filter desaturates that master to pure luminance and re-maps it onto a colour ramp built from the chosen colour — shadows to a darkened version, midtones to the colour itself, highlights to a lightened version. The product's own lighting is preserved, so a recoloured shot still reads as a photograph rather than a flat silhouette.

The visitor picks from a set of named swatches — no raw hex or RGB input, just "olive", "terracotta", "anthracite" — and the preview updates on the same frame. Because a custom colour is a special order rather than a stock SKU, the chosen colour name is reported back up to the product form and pre-filled into the order request, so what the buyer saw is exactly what the shop receives. Swatch labels run through the same next-intl dictionary as the rest of the catalogue, so the colour names are localised alongside everything else.

Try It

This is the exact recolour that runs on the product page — the same transform, live in your browser: the product's white master is painted with a diffuse tint plus a white specular highlight. Pick a colour and pull the sliders: saturation, shadow depth and highlight are the transform's real knobs.

Results

Under the Hood

For the technically curious, here's how the live preview is built.

One Filter, Any Colour

The core is an SVG filter that turns a product photo into pure brightness, then paints that brightness with the target colour. feColorMatrix with saturate 0 collapses the image to luminance; feComponentTransfer then rewrites each channel through a three-stop table — shadow, base, highlight — derived from the target colour. The shadow stop keeps folds and contours dark; the highlight stop keeps sheen; the base stop is the colour itself.

const SHADOW_MUL = 0.28;
const HIGHLIGHT_MIX = 0.68;
 
function hexToRgb(hex: string): [number, number, number] {
  const v = hex.replace("#", "");
  return [
    parseInt(v.slice(0, 2), 16) / 255,
    parseInt(v.slice(2, 4), 16) / 255,
    parseInt(v.slice(4, 6), 16) / 255,
  ];
}
 
// 3-stop luminance ramp per channel: shadow -> base -> highlight.
function ramp(channel: number): string {
  const shadow = channel * SHADOW_MUL;
  const highlight = channel + (1 - channel) * HIGHLIGHT_MIX;
  return `${shadow.toFixed(3)} ${channel.toFixed(3)} ${highlight.toFixed(3)}`;
}

The filter itself is a few static nodes; only the tableValues change when the colour changes, and React re-renders just those three strings:

const rgb = hexToRgb(selectedHex);
 
<filter id={filterId} colorInterpolationFilters="sRGB">
  <feColorMatrix type="saturate" values="0" />
  <feComponentTransfer>
    <feFuncR type="table" tableValues={ramp(rgb[0])} />
    <feFuncG type="table" tableValues={ramp(rgb[1])} />
    <feFuncB type="table" tableValues={ramp(rgb[2])} />
  </feComponentTransfer>
</filter>;

Applying it is a single CSS property on the image — the recolour rides the GPU compositor, not a redraw:

<img src={src} style={{ filter: `url(#${filterId})` }} loading="lazy" />

Transparent Masters, Derived From the Catalogue

The catalogue only stores the stock photo paths (12-black.webp). The picker derives the transparent master path from those by convention, and quietly drops any image that has no master (diagrams, mesh close-ups), so the preview only ever shows the shots that can actually be tinted.

function transparentMasters(images: string[]): string[] {
  const out: string[] = [];
  for (const src of images) {
    const m = src.match(/^(.*\/)(\d+)-(?:black|grey|white)\.(?:webp|png)$/);
    if (m !== null) out.push(`${m[1]}${m[2]}-transparent.png`);
  }
  return out.slice(0, 3);
}

The Colour the Buyer Saw Is the Colour They Order

A custom colour isn't a stock SKU, so it can't just be added to the cart — it becomes a special-order request. The picker reports the chosen colour name (already localised) up to the product form, which pre-fills it into the enquiry. There's no second place for the buyer to re-state the colour, and no gap between the preview and the order:

const [customColorName, setCustomColorName] = useState<string | null>(null);
 
<CustomColorPicker images={images} onChange={setCustomColorName} />;
// ...the form's colour field is driven by customColorName