Tactile Image

any picture, read with your fingers

Turn any picture into something you can read by touch. A photograph, a map, a scanned plan, a diagram, a logo — drop it in and it becomes a plate for PIAF swell paper, where every black mark rises into a ridge. This is not a halftone: a halftone turns grey into small dots, and under a fingertip small dots are just noise. Instead the picture is simplified and textured — its tones are sorted into two to twelve bands, each filled with a pattern you can tell apart by touch (smooth, dotted, ruled one way, ruled the other, crossed, solid), with a groove of blank paper between neighbours so no two textures run together. Line work is thinned to its centre and re-drawn at a real ink weight, so every ridge stands the same height, and anything smaller than a fingertip can resolve is dropped rather than printed as a smudge. Every rule is set in millimetres of ink on paper. The key carries each band’s texture as a swatch at its true pitch, with what it means beside it in print and underneath it in Braille — under the picture, or on a sheet of its own so nothing competes with the drawing under the hand. It takes PDFs as well as pictures, and a PDF page knows how big it prints: drop in a plotted 36 × 36 in sheet and it tiles across as many pieces of 8.5 × 11 or 11 × 17 PIAF paper as it needs, each one numbered in print and Braille. And because most drawings arrive as a photograph OF a drawing, the whole Drawing Cleaner — straighten, crop, levels, curves, uneven-lighting, despeckle, sharpen, threshold — runs here first, in front of the converter. The bands split on the picture’s own histogram, or where you drag the boundaries; every band can be fine-tuned on its own — pitch, ridge width, angle — or filled with any of the Gardener’s 77 pattern tiles, the same library Tactile Drawings uses. A loupe with a millimetre ruler and a fingertip overlay true to the sheet check the plate before it prints, and on a tiled set the sheet labels live in a footer below the picture, never on it.

The converter reports what it did to the pixels — it does not know what the picture shows. Naming the bands in the key is how meaning gets onto the sheet, and it is worth doing before you print.

Picture

—

The demo drawing is a photograph of an inked page — warm paper, uneven light, blue under-drawing — so it fails the way your own scan will, and the clean-up stage above has something real to fix. The demo massing is a flat synthetic card, for working on tone bands rather than line work.

Photos, maps, scanned plans, diagrams, logos — and PDFs, which are the useful case, because a PDF page knows how big it is meant to print. Drop in a plotted 36 × 36 in sheet and it lays itself out across as many pieces of PIAF paper as it needs. Nothing is uploaded; the file is read in this tab and stays there.

Clean up the scan

Most pictures of a drawing are photographs — lit from one side, on grey paper, slightly crooked. Fix that here, before the converter sees it. The converter’s own tone controls cannot rescue a scan whose paper reads as mid-grey; they only decide how honest tone becomes texture.

Off means the converter reads the picture exactly as it arrived. Straighten and crop below work either way.

Drag the two lines onto the ends of the hump: B is where the darkest ink goes solid, W is where the paper goes clean white.

■ Black 0γ 1.0White 255 ■

Drag the white handle down onto the paper peak and the black handle up onto the ink peak: the paper goes white, the lines go black, and the converter finally has something to band.

The Drawing Cleaner’s output modes — keep-colour, tint, and its own Invert — are not here: a swell plate has exactly one ink and one paper, and light/dark is flipped once, by Invert under Treatment. Everything else that tool does, this does.

Treatment

Light becomes dark — for white-on-black scans.

mm
What a fingertip can read
mm

A fingertip resolves about 2 mm. Anything smaller than this is dropped, and any hole smaller than it is filled.

mm

Blank paper held open between neighbouring textures, so two of them never run together into one shape. It is always taken out of the lighter side.

mm

Centre to centre of the ruling. Tighter reads darker and heavier; under about 2 mm the ridges start to fuse into a flat field.

mm

How thick each ruled line is. The default is deliberately THIN — a heavy ruling at a close pitch swells into a solid and the tone ramp loses its middle.

×

A multiplier on every pitch, dot lattice, checker square and tile edge on the plate — the plate's own and each band's override alike. ×1 is as set.

×

A multiplier on every ridge width and dot size. Watch the ink density: past about ×2 at a 3 mm pitch a ruling swells into a solid.

These are the numbers that make it tactile rather than merely black and white — all in millimetres of ink on paper, the same units a 3D printer is dialled in, and the units Braille itself is specified in. A fingertip resolves about 2 mm; ridges closer than that read as one. Anything smaller is dropped rather than printed as a smudge.

%
Method: Percent of the one-sheet size: 100 % is the width the picture prints at when fitted to one 8.5 × 11 in (letter) sheet with this margin and title block (7.0 in). The printed width is that times the percent; past 100 % the plate tiles across as many sheets as it needs.
in
Method: The printed width of the picture in inches — the same size as the percent above, typed as a length. Wider than the sheet is legal: the picture tiles, each sheet packed to the margin so the pieces butt together when trimmed.

7.0 × 7.0 in — one sheet of 8.5 × 11 in (letter), portrait.

No picture yet — drop one in.

The preview converts at about 6.9 pixels per millimetre to stay live under the sliders; every download re-runs the whole conversion at 12.0 px/mm and writes the sheets at 12 px/mm (≈305 dpi), so nothing you save is the preview enlarged.

Tone bands → textures

Off: a one-dimensional k-means (Lloyd's algorithm) on the histogram above finds the splits, so the same picture always bands the same way.

  • Band 1 · darkest
  • Band 2 · middle
  • Band 3 · lightest
Sheet
Paper (PIAF sheet)
mm

Only when there is more than one sheet. The footer is sized for the longest label, taken out of the picture window so every sheet crops the same; the trim rule marks where the picture ends.

The picture prints 7.0 by 7.0 inches (178 by 178 mm) — as large as one sheet allows — on ONE sheet of 8.5 × 11 in (letter), portrait, with a 5 mm margin. The printed size is set in the Print size bar above the sheet.

Relief print — when the PIAF is down

The same sheet as a thin 3D print: a base a few layers thick, every inked mark raised a few layers above it — what the swell paper would have raised — and, if you want it, each tone band on its own terrace. Heights are whole printer layers, never fractions. Write it from Export → Relief STL; see it under Relief print in the middle of the page.

mm

Each darker band stands this much above the next lighter one; the lightest sits on the base. The texture ridges ride on top of every terrace.

mm

A sheet wider than the bed is cut into pieces that each fit it — the same presets and the same clearance Relief prints with.

in
  • No plate yet — drop a picture in, and the relief print describes itself here.
Title, key & description

The key draws each band’s texture as a swatch at the very pitch it is printed at, so a finger can run from the swatch into the picture and check they match. Braille is real dots (1.4 mm on a 6.2 mm cell), true size.

Read-back

What the converter did, in words — kept current as you work, and embedded in the SVG export as its description.

  • No picture yet — drop one in.
Tactile Image · Good Tools