Blend
The colour mixer — Blend, Blur and Fingertip, what an affine blend stroke is, and why the tool carries no colour of its own.
Reference
- Tool
- Blend
- Panel
- Tool Options
The Blend tool mixes the colours already on the canvas. It has no pigment of its own — its Tool Options carry no colour well, because nothing it does consults one. Rub it across a boundary and the colours on either side move into each other; rub it over flat colour and nothing happens, because there is nothing to mix.
A blend stroke does not edit the strokes beneath it. It is an ordinary stroke appended on top, whose pixels are the result of the mixing — which means a smudge is undoable, erasable and re-orderable like any other mark, and the artwork under it is never destructively touched.
What an affine stroke is
A blend stroke stores two things per pixel: the paint it deposited, and a transmittance —
how much of what lies below still shows through. It composites as deposited + below × transmittance
rather than as ordinary source-over paint.
The transmittance channel is what makes mixing possible at all. Dragging picked-up transparency into solid ink has to reduce the composite's alpha, and plain source-over compositing can only ever add. Without a transmittance channel a smudge could darken an edge but never erode one.
Sub-tools
The three mixers are rows in the Sub Tool panel, and are also selectable from the tool's own options. Each row previews its behaviour as a red-to-blue capsule: a smooth melt, a defocused band, a streak pulled to the right.
"Melt neighbouring colours into each other."
Soft continuous pickup with moderate deposit: the brush keeps absorbing what it passes over and keeps laying it back down, so colours melt together along the stroke. The tool's own hint reads "Rub across a colour boundary to melt the colours together. Pressure drives the strength."
"Soften what's under the brush — nothing smears."
Non-directional softening: it deposits a small gaussian of whatever is under the tip. Nothing is dragged anywhere, so detail dissolves in place and edges lose their definition without travelling. The tool's own hint reads "Rub to soften what's under the brush — edges and detail dissolve, nothing smears."
"Drag colour along like wet paint under a finger."
A true smudge: it loads the paint under the tip at the start of the stroke and drags it — strong deposit, weak pickup, so the colour it started with travels a long way and produces long streaks rather than a local melt. The tool's own hint reads "Drag to pull colour along like wet paint under a finger — long streaks, strong pull."
Tool Options
Blend, Blur or Fingertip. The same choice as the Sub Tool panel's rows.
The mixer's diameter, on a logarithmic scale.
How far each dab moves the canvas toward the colour it has picked up, displayed as a percentage. The floor is 0.05 rather than 0: a strength of zero is a tool that silently does nothing, which reads as broken rather than weak.
The blur kernel radius, as a fraction of the brush radius, displayed as a percentage. Shown only while the sub-tool is Blur; the other two mixers do not read it.
QuickStrip
The strip shows the mixer's Size and its Strength — not a paint opacity, which the Blend tool has no use for. The colour well below the divider is present for every tool, but Blend does not consult it.
| Knob | Range | Default |
|---|---|---|
| Size | 0.5–1000, logarithmic | 60 |
| Strength | 0.05–1 | 0.45 |
Brush Settings
The Tip section shows the Size and Strength knobs and one line — "Rub to mix the colours already on the canvas. Pick Blend, Blur or Fingertip in Sub Tool." None of the paint sections appear: there is no tip, no spacing and no scatter to describe.