Commit Graph
7 Commits
Author SHA1 Message Date
dtourolle 68ebf5d78b Let a mask start from a tone or a colour, not only a shape
Every local adjustment began from a shape: painted, drawn with a handle, or
found by a model. So the only way to hold back a sky was to draw a line near
where it ended, and the only way to warm skin was to paint round it — both of
which put the edit's edge where the photographer put a gesture rather than
where the picture changes. A gradient across a treeline halos, and an
adjustment traced round a face stops on the outline of a hand.

MaskSource grows two variants that select by what a pixel *is*. Luminance
carries two bounds on the perceptual tone scale plus a softness; Colour carries
an arc of hue, a range of chroma, and one softness for every edge of both. Five
floats and three, so they diff, sync and merge per field under FR-NC-9 exactly
as a gradient's geometry does — the property a stored raster has none of, and
the reason the model's coverage had to sit beside its source rather than inside
it.

The pixels are the shader's business and nowhere else's. `mask.wgsl` takes the
demosaiced source as a sixth binding and two new modes read it: decode, balance,
pull a clipped photosite back to neutral, apply the camera matrix, then weigh
the band. Nothing crosses to the CPU but the numbers and the matrix, and each
mask texel averages its own footprint in the source, so a band lands on the tone
an area is rather than on whichever texel a proxy grid happened to land on.

The photograph it measures is the one the camera recorded, before this edit. A
band over the edited result would slide out from under the edit as the edit was
made — raising the highlights would change which pixels counted as highlights,
and the slider would chase its own mask.

Feather, falloff and morphology stay off a range layer, which is what
`shapeable` already meant. All three are functions of the signed distance from
a boundary, and a range has no boundary to be at a distance from; its edge is
the softness of its own band, in the band's units. Offering them would be four
controls that move and change nothing.
2026-09-06 19:01:48 +02:00
dtourolle 5bcd0e0269 Merge branch 'worktree-agent-a22a049c461818dbe' into integration
# Conflicts:
#	core/dr-pipeline/tests/mask_sidecar.rs
2026-08-22 13:23:34 +02:00
dtourolleandClaude Opus 5 c75863c93f Give a gradient the angle it was asked for
A linear mask at 45° was not at 45°, and a radial with equal radii was an
ellipse. Both on every photograph that is not square, which is all of them.

The geometry is stored in normalised coordinates so that a mask survives a
crop, a zoom and an export at another size — that part was right. What was
wrong is that a *distance* was being measured in those coordinates too, and a
fraction of the width is not the same length as a fraction of the height. So
`dot(uv - centre, axis)` measured the ramp in a space one of whose axes is
squashed against the other by the aspect ratio, and the iso-lines came out
sheared: on a 3:2 frame a ramp asked for at 45° arrives at about 34°.

Nothing announces it. The stored numbers are exactly what was written, the
shader is doing exactly what it says, and the only place the fault exists is
between the photographer's intent and the picture. It has been invisible so far
because there is no way yet to place a gradient by eye — the handles that make
it visible are what turned it up.

So distances and angles move into the frame's own isotropic units: y spans
`0..1` and x spans `0..aspect`, which makes a circle round and 45° a real
diagonal. The centre stays a plain fraction of each axis, because it is a point
and a point has no such problem — and because that is the space a click arrives
in. `frame_delta` is the one conversion and must stay the only one; the mask
array's own dimensions carry the aspect, so it costs no uniform.

The sidecar format does not change. What changes is what the numbers mean, and
the only geometry in the wild is a default that has never been movable.

The two tests are at 96×64 rather than square, which is the whole point: on a
square target this bug cannot be reproduced, and every existing mask test was
square. Both fail without the conversion — the radial reaching 28px sideways
where it reaches 19px down, and the diagonal landing on the wrong side of the
line it is supposed to lie along.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-22 13:19:55 +02:00
dtourolleandClaude Opus 5 c396a22dfd Paint a mask without ever rasterising one on the CPU
The last line of FR-DEV-3, and the mask ARCH §5.4 was written for. darktable
rasterises drawn masks on the CPU and users call the result unworkable; the
architecture's answer is that a stroke arrives as *parameters* and the device
draws it. This is that, from the model through the sidecar to the pixels — but
not the finger: the canvas is somebody else's change, and this leaves it a
seam rather than reaching into it.

**A stroke is a swept disc along a polyline**, plus erase, radius, hardness and
flow. `MaskSource::Brush` holds an ordered list of them, and the order is the
mask: an erase after an add takes it away and the same pair reversed does not.
Nothing about it is pixels, which is what makes a mask that costs a line of
text, diffs by the gesture, and survives a crop, a straighten and an export at
any size — the properties a stored raster has none of, and the same argument
the region ids were chosen for.

Two things keep the point count honest. While the finger is down, a position
closer to the last than an eighth of the radius is dropped: a touch screen
reports 120 a second, so a finger held still for five seconds is six hundred
points in the same place, and simplification would only remove them once the
gesture had ended — after every frame in between had drawn all of them. When
it ends, Douglas–Peucker at an eighth of the radius removes what a disc that
wide cannot express: a swept circle moved by r/8 moves its own edge by r/8,
which is inside the soft part of any brush. Coordinates snap to a
ten-thousandth of the frame on the way in *and* are written at that precision,
so a round trip is exact rather than nearly exact — a file that drifts in the
sixth decimal every save is a per-field merge conflict a day, over nothing.

**Cost is why the strokes are not drawn by the full-screen triangle the other
masks use.** A swept disc is the minimum distance to any of its segments, so a
stroke over the whole frame costs `pixels × segments` and both terms grow
together — the quadratic that is darktable's problem moved onto the GPU rather
than solved. Each stroke is instead drawn over its own bounding box, grown by
the radius, so the rasteriser never invokes the shader for a pixel the stroke
cannot reach: `area(box) × segments`, which for a dab or a swipe is a small
fraction of the frame. A gesture past 256 points continues as a second stroke
for the same reason, since a shorter stroke has a smaller box.

Add and erase are `dst + a(1 - dst)` and `dst(1 - a)`, which are exactly a
source-over and a one-minus-source blend — so they are blend state, not
arithmetic, and no pass ever reads the slice it is writing. That is what
permits one draw per stroke at all. Within a stroke the coverage is the
*minimum* distance over its segments rather than a sum: a path that crosses
itself must not build up where it did, or every circle and every scribble
would be blotchy wherever consecutive dabs overlap, which is everywhere.

Not a distance field, deliberately. `dr-segment`'s transform documents the two
conditions that make CPU work right there — once per mask edit, over input
already CPU-side — and a stroke fails both: it changes while the finger moves,
and its input is a handful of coordinates that never needed to be pixels. It
also needs no transform, because the distance to a swept disc is closed form.
A stroke is the one mask whose distance field is known without computing one.

An unpainted brush layer is inactive rather than empty, which is not an
optimisation: `invert` turns empty into everything, so a layer created with
invert already set would apply its adjustment to the whole photograph before a
single stroke was made. That is the loud, confident kind of wrong this codebase
refuses everywhere else a mask can go missing, and there is a rendered test for
it.

The tests read pixels back off a device rather than checking that the two
halves agree with each other. What they pin down is what is silent when wrong:
the y flip between mask space and clip space, which a centred stroke would not
notice; a bounding box not grown by the radius, which makes a tap draw nothing
at all; an aspect ratio ignored, which makes a dab an ellipse on any frame that
is not square; a stroke doubling back and building up; and an erase that lost
its place in the order and put back paint the user had taken off.

Not done here: the interaction. The canvas needs to begin, extend and end a
stroke on the active layer, and `DevelopSession::rasterise_masks` still returns
early without a segmentation — it takes the proxy size from one, and a brush
needs no model to have run over the photograph first.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-22 12:37:42 +02:00
dtourolle ec713585a5 Measure the distance to the edge, and get four controls for one transform
Feathering, growing, shrinking, closing and opening are the same number
read differently. With the signed distance from the boundary in hand,
dilation is the set where d >= -r, erosion where d >= +r, and a feather of
any shape is a function of d. So the field is computed once and the
controls are arithmetic on it.

The **field** is what reaches the GPU, not a finished alpha, and that is
the point: growing a mask or changing its falloff then costs a uniform
upload and no recomputation, which is what makes them live controls rather
than ones that stall on every drag. Only closing and opening rebuild,
because after the first threshold the shape has changed and the old
distances describe the old one.

Exact Euclidean, via Felzenszwalb's separable transform — not a chamfer
approximation, which leaves a mask visibly octagonal once grown more than
a few pixels. A test asserts the diagonal is √2 rather than 1 or 2.

It runs on the CPU, which ARCH §5.4 forbids for masks. The rule is about
brush lag — a stroke rasterised per frame — and this is a different
operation: once per mask edit, on input the model already produced here,
producing a field the GPU then samples for free. What it buys is exact
determinism, which matters because masks reach the sidecar as indices and a
field that varied by vendor would mean a mask meaning one thing on the
desktop and another on the phone.

The half-pixel in `signed_distance` is not a detail, and a test caught it.
Measuring to the nearest opposite pixel *centre* puts the smallest
magnitude at 1 either side, so the boundary is nowhere and **eroding by
less than a pixel removes nothing**. A control whose first notch does
nothing is a broken control. Half a pixel off each side puts the boundary
where it physically is, and eroding by 1 takes exactly the outermost ring.

Every falloff curve is 0.5 at the boundary by construction, asserted for
all five: changing the curve should change how the transition looks and
never where it sits.
2026-08-22 08:39:17 +02:00
dtourolle ee10097435 Mask the subject the model found, not the regions underneath it
The watershed hierarchy does not survive a photograph, so local masking
stops depending on it. A layer can now be one recognised object, and the
object's own coverage is the mask.

`Options::watershed` defaults off. It costs ~80 ms plus a full-resolution
readback to produce a ladder that collapses, and paying that on every
photograph buys a control that misleads. Kept switchable rather than
deleted: the passes and the hierarchy are correct in themselves and it is
the merge criterion that fails, which is a change to one function.

Masks now rasterise in **source** space at proxy resolution and are sampled
by the composed shader after the framing map. That fixes a real bug: they
were rasterised in output space, so zooming slid the photograph underneath
a mask that stayed pinned to the viewport, and cropping moved every
adjustment to a different part of the picture. Doing it this way also
leaves the framing map in exactly one place — a second copy in the mask
shader would have been a second thing to keep in step, failing only when
straightened.

A subject is stored as identity, not pixels: the mask is megabytes and is
reproducible by running the same model over the same image, so the sidecar
carries the index, the class and the score, and the session carries the
pixels. The class is there to be checked — if instance 3 comes back a "car"
where it was a "dog", something changed and the layer is stale rather than
silently masking the wrong thing.

The overlay now draws instances and is transparent everywhere else. The
region version covered every pixel and so hid the photograph it was drawn
over; the question it exists to answer is whether an outline follows the
subject, which you can only answer by seeing both.

`examples/local.rs` is the worked example: subject in colour with the rest
monochrome, and the subject lifted out of its background. Run on a 5472x3648
CR2 it finds two people and two cars, and the colour-pop keeps her hat and
hair while the wall and grass behind go grey.
2026-08-22 08:39:17 +02:00
dtourolle c6a846a1f9 Brighten her face without touching the sky behind her
A mask layer is an ordinary develop chain plus a rule about where it
applies. Nothing in the chain knows it is being masked, so every operation
that works globally now works locally and a newly declared op in `ops/`
arrives with local support already done.

The composer emits each layer after the global chain and before the
conversion out of camera space, which is what a photographer means by "and
*then* lift the shadows on her face". Op fragments write to a `c` they
expect to own, so a layer block shadows it and copies the result back out
through a carrier — assigning the outer one from inside is impossible
precisely because it is shadowed. The fused dispatch survives: three global
adjustments and two masked ones remain one shader, one read, one write.

Masks rasterise on the GPU and never exist in CPU memory (ARCH §5.4). That
is the whole reason darktable's brush masks lag, and it is architectural
rather than tuning, so it is not a thing to inherit and fix later.

The rasteriser is a render pass rather than the compute shader it obviously
wants to be, and the format is why: R8Unorm is not a core storage format,
so a compute path has to widen masks to four bytes per pixel — 768 MB
across eight layers of a 24 MP export, against 192 MB at one byte. A colour
attachment takes R8Unorm happily. The array slice comes from the attached
view, so no slot uniform exists to disagree with where the pass writes.

Region masks index a compacted label field rather than the watershed's raw
basin roots, because a root is a sparse index into pixel space and
indexing a per-region array by one would need a table the size of the
image. Changing a selection then costs a few kilobytes, not a re-upload.

Stored as region ids, not as pixels: diffable, mergeable per-field under
FR-NC-9, and cheap in a sidecar. The ids only mean anything alongside the
segmentation that produced them, so each layer carries that signature and
is treated as stale rather than applied when it does not match — a
confidently wrong mask being much worse than an absent one.

Seven device tests render actual frames and read them back. The unit tests
either side check halves that would both pass if the two agreed with each
other and were both wrong; a mask sampled with x and y swapped satisfies
them and fails these.
2026-08-22 08:39:16 +02:00