HowMany.pro

See the panel in the doorway before it exists

Nobody buys a leadlight from a pattern on paper. Photograph the opening, drag four corners onto it, and the panel drops in behind the photo at the same angle, lit from behind, glowing onto the wall - then goes to the customer as one picture.

Leadlight In Placev1.1howmany.pro
x - y -zoom 1.00xLoad a photo of the doorway or window to start.

A photo of the doorway, window or wall opening. Any angle: the fit corrects it.

Stand square-ish to the opening if you can, but any angle works - the four corners tell the tool the perspective. The photo never leaves this browser.

Openings

A front door with two sidelights is three openings. Copy this one keeps the panel and the light, so you only drag the corners.

Dims the photograph, nothing else. It is how you show a customer what the panel does after dark.

The panel is a layer behind the photograph

The order matters, and it is the reason this works at all. The photograph of the doorway is the top layer with a hole cut in it - the opening you marked. The panel sits behind, so it can be slid, scaled, stretched and turned freely and it will never spill onto the architrave or the wall. Anything you push past the edge of the opening simply disappears behind the photo, exactly as glass does behind a rebate.

The four corners you drag are the whole interface between the two layers. They define a homography: eight unknowns, solved from four point pairs, applied to every pixel of the panel. A projective transform of this kind keeps straight lines straight and keeps the cross-ratio of any four points on a line, which is why a border band photographed at an angle still reads as a band of constant width narrowing correctly into the distance - and why a simple stretch or a rotation, which is all a photo editor gives you, never does.

Snap to the edges is the tidy-up. Once the corners are roughly on, it takes each of the four sides in turn, slides it perpendicular to itself across a few per cent of the picture, scores each position by how strong a light-to-dark step it sits on, keeps the best, and then re-intersects the four lines to get the corners. It is the same idea a document scanner uses on a page edge, and it saves the last two minutes of squinting.

Backlight, and why a panel on a bench always disappoints

Glass is the only material in a house that is designed to be seen with the light behind it. Cathedral glass is transparent coloured glass: under reflected light it is close to grey, and it only shows its colour when a source is behind it. Opal or opalescent glass carries an opacifier - historically bone ash or fluorides - which scatters light inside the sheet, so it reads as a solid colour from either side and glows rather than transmits. A panel photographed lying on a workbench is being lit entirely the wrong way, and that photograph is why so many quotes go quiet.

The light control here does what light actually does, rather than brightening the picture. The lit pass is a screen blend of the panel onto itself: bright, transmitting glass gains a great deal, and the came - the lead, which transmits nothing - gains almost nothing, so the pattern goes dark against glowing glass exactly as it does at four in the afternoon. The glow is that same lit panel, blurred and tinted, thrown onto the wall and floor around the opening, because a real backlit panel spills coloured light into the room.

Colour temperature is the part people get wrong. A hall lamp behind a front door is around 2700 K and pushes reds, ambers and golds up hard; that is not a coincidence in Federation-era hall panels, which were designed under gas and early tungsten light and are full of exactly those colours. Overcast daylight is nearer 6500 K, flattens the warm colours and lifts blues and greens. Set the room to night with a warm lamp and a design can look like a different panel from the same design at noon - so show the customer both.

A door is usually three openings, not one

A standard Australian entry is a door light with a sidelight either side, or a door with a highlight over it; a bay window is three or five. Mark one opening, get the panel and the light right, then press Copy this one and drag the four corners onto the next. The copy carries the panel, the fit and the light with it, so the second and third take about fifteen seconds each - and, more usefully, they carry the same design at the same scale, which is what makes a set of lights look like a set.

The proportion check runs on every opening. If the design is coming from the Leadlight Designer it knows its finished size in millimetres, so the tool compares the shape of the marked opening against the shape of the design and says plainly when the panel is being stretched more than about six per cent out of its own proportions. That is the point at which a border band stops looking like a border band, and it is much easier to fix on the screen than after the glass is cut.

Sending it

The picture is built at up to 2400 pixels wide, which is enough for a phone screen, an email and an A4 print. Send it hands the finished image to your device's own share sheet through the Web Share API - the file-sharing part of it has been in Chrome since version 75 and in Safari since iOS 15, so on a phone it lands straight in Messages, Mail or WhatsApp. On a desktop browser without a share sheet, Copy it puts the image on the clipboard to paste into a mail, and Save the picture writes a PNG.

Tick Put the empty opening beside it and you get the before and the after in one image. It is the version worth sending: on its own, a mockup invites the question "is that really my door?" - beside the untouched photograph, it answers it.

Questions from the bench

How does the panel end up at the same angle as the photo?
Four corner pairs are enough to fix a projective transform - the panel's four corners, and the four you drag onto the opening. That is eight numbers, and eight is exactly what a homography has. Once it is solved, every straight lead line in the panel stays straight in the photo and the foreshortening matches, which is what a flat panel in a flat opening actually does. It is the same maths a scanner app uses to flatten a photographed page, run the other way round.
Can I use a photo taken from the side?
Yes, and it will still look right. What you lose at an extreme angle is resolution, not accuracy: the far edge of the panel is being drawn into very few pixels. About 30 degrees off square is the point where a mockup starts to look soft rather than convincing.
Does my panel have to be designed in the Leadlight Designer?
No. Any image works - a PNG with a transparent background, an SVG, a scan of a cartoon, or a straight-on photograph of a panel you have already made. A design saved in the Leadlight Designer in this same browser shows up in the list on the Panel step without exporting anything, and it arrives with its real millimetre size, so the caption and the shape check are exact.
Why does the glass look better with the light behind it?
Because that is the only way glass is meant to be seen. Cathedral glass is transparent and does almost nothing under reflected light; it needs a source behind it to show its colour. Opal glass is the opposite - it is loaded with opacifier so it scatters light and reads as a solid colour from both sides. That is why a panel photographed flat on a bench always disappoints, and why the light slider matters more than any other control here.
What colour should I set the light to?
Match the shot. A hall light behind a front door at night is a warm lamp at roughly 2700 K, and it pushes every red, amber and gold up - which is why Federation-era hall panels are full of them. Overcast Australian daylight is nearer 6500 K and flattens the warm colours while lifting blues and greens. If you are showing a customer a night shot, set the room to night and the light to the warm lamp; for a daytime shot, cool daylight and no room dimming.
Is the mockup accurate enough to quote from?
It is accurate for shape, proportion and colour balance, and honest about fit: if the panel is being stretched more than about six per cent out of its own proportions the tool says so. It is not a measurement. Measure the opening with a tape, into the rebate, and take the sight size from that.
Does the photo of my house get uploaded?
No. Reading the photo, warping the panel, the light, the export and the autosave all happen inside this browser tab. The only thing that leaves your machine is the picture you choose to send, and you send that yourself.
Sources
  • Projective geometry: a plane-to-plane homography has 8 degrees of freedom and is determined by four point correspondences in general position - Hartley & Zisserman, Multiple View Geometry in Computer Vision, 2nd ed., ch. 2
  • Opalescent glass: opacifiers (bone ash, fluorides) scattering transmitted light - the property Tiffany and La Farge patented competing versions of in 1880
  • Colour temperature: incandescent / warm LED lamps approx. 2700 K, overcast daylight approx. 6500 K (CIE standard illuminant D65)
  • Web Share API Level 2 (sharing files): Chrome 75+, Safari on iOS 15+ - MDN Web Docs, navigator.canShare()
  • Came face widths and the 1.6 mm heart, as used for the sample panels: standard H-section lead came profiles sold by stained glass suppliers

A pattern is a promise about light. This is the first place anyone can see whether it will be kept.