Commit Graph
8 Commits
Author SHA1 Message Date
a62ef68ca2 CMYK: Hue/Saturation and Color Balance keep the black ink (#5000)
* Modern Brightness/Contrast: Photoshop's brightness curve

The modern brightness curve was a line rolled off by a v^P term. It sat
up to 4 levels off Photoshop's in the highlights, and up to 2.3 levels
off for lowered brightness.

The curve is refit to the Photoshop ground truth we have:
- the ±50 samples from 4759d12b;
- the photoshop corpus's brightness +25 / contrast +30 files,
  inverted through the (exact) contrast curve.

Raised, it is the line s*x (s = 1.375^(b/50)) up to a knee at 80/255,
then a cubic Hermite to white with end slope s^-6.6. Lowered, it is the
exact inverse of the curve raised by as much (the -50 samples confirm
this to within a level). Every measured point is within about a level.
For strong values the knee moves down so the curve stays monotone
across -150..150.

Brightness then contrast are evaluated through one 4096-entry table,
built in 55 us. The GPU uses that same table through the Levels/Curves
kernel instead of rebuilding the curves in WGSL, so GPU and CPU agree
by construction.

Photoshop oracles: rgb8/16/32 and gray8/16/32 brightness-contrast now
pass (145 -> 151 of 258). The floor goes 133 -> 151.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: Brightness/Contrast curves each ink, as Photoshop does

Photoshop applies Brightness/Contrast in a CMYK document to each ink's
stored value, 1 - ink, black included. Both the modern and the legacy
curve do this; the cmyk8 brightness-contrast(-legacy) oracles match it
within a level on every pixel of the files' own inks. Raising
brightness takes ink away. We applied it to the screen colour instead.

- cmyk_channel_adjustment gains Brightness/Contrast. apply_in builds
  the channel curve once (brightness_contrast_lut) and runs each
  separated ink through it (ink_through).
- Destructive Image > Adjustments on a CMYK layer curves the stored
  inks directly, so it is exact; a selection mixes them.
  adjusted_channels now takes the per-pixel operation, and works out
  luma only for CMYK Threshold, which compares it.
- The GPU leaves CMYK Brightness/Contrast to the CPU, like the other
  ink rules.

cmyk8/16 brightness-contrast oracles, bad pixels:
- modern: 72% -> 48-57%, max error 0.19 -> 0.09
- legacy: 71% -> 51-53%

The rest is our separation of the RGB composite, not the rule.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK Threshold compares the inks' own luma, as Photoshop does

Photoshop's CMYK Threshold splits on the Rec. 601 luma of the inks' plain
complement, (1 - c)(1 - k) and so on, whatever the document's profile.
On the files' own inks this puts every pixel of cmyk8 and cmyk16
threshold-128.psd on the right side of level 128. The profile's RGB luma
missed 100.

stored_channels works the luma out from the inks itself (ink_luma), so it
no longer takes one; the engine's stored-channel path no longer converts
each pixel to RGB at all. Through the separated RGB composite the cmyk
threshold oracles drop from 1.6% to 0.2% bad pixels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK legacy Brightness/Contrast pivots at 128 in ink

Photoshop's legacy contrast pivots at level 128 of the ink, which is 127
of 255 of the stored value (1 - ink) that the curve runs on, not 128 as
in RGB. On Photoshop's own 16-bit inks (cmyk16
brightness-contrast-legacy.psd) ours sat a constant 0.43 of a level
above. That is exactly the one-level pivot shift times contrast +30's
slope minus one; with the pivot moved, the inks match within 0.01.

brightness_contrast_lut is now ink_brightness_contrast_lut, since its
legacy curve is the CMYK one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: adjustment layers composite on the document's own inks

The compositor works in display RGB. In a CMYK document, an adjustment
layer that Photoshop evaluates on the inks could only act on our
separation of the RGB composite, and that separation's black differs
from the file's. So even exact ink rules missed: CMYK Invert was 10%
off, Levels and Curves 50-65%.

The ink-native compositor (compose::native, until now only for
flattening plain raster stacks) now takes adjustment layers too:
- Invert, Posterize, Threshold and Brightness/Contrast (modern and
  legacy), and Levels and Curves on CMYK channels, prepared once
  (InkStack, InkOp) and applied to the straight inks.
- Opacity and an unfeathered layer mask mix the inks linearly, as in
  Photoshop; raster layers' masks scale their coverage the same way.
- A CMYK stack of plain raster layers and such adjustments renders this
  way for display, export and reduced views (render_cmyk, tiles in
  parallel); flattening and merging keep the adjusted inks exactly.
- Stacks of raster layers alone keep the RGB compositor, which the GPU
  matches. The GPU already leaves these adjustments to the CPU.

Photoshop oracles: cmyk8 and cmyk16 invert, posterize-4, threshold-128,
levels, curves, brightness-contrast and brightness-contrast-legacy all
pass (14 files), 151 -> 165 of 258; floor 151 -> 165. psd-tools and io
corpora unchanged. 24 MP CMYK8 with one adjustment renders in 286 ms on
the inks, against 442 ms through the RGB compositor.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK ink compositing inlines open groups

The ink compositor gave up on any group. Now a group at full opacity
without a mask is inlined:
- a pass-through group's children composite straight onto the backdrop,
  so an adjustment inside it reaches the layers below;
- an isolated (Normal) group of raster layers alone composites as its
  children would, since Normal is associative.

An isolated group with an adjustment, which only sees the group's
content, keeps the RGB compositor. So do a translucent group and an
artboard. Nesting is bounded.

psd-tools' CMYK adjustment files keep their swatches in pass-through
groups. With #4948's fair comparison, curves_cmyk drops from 37% to 0.3%
bad pixels and levels_cmyk from 14% to 0.2%. The photoshop corpus is
unchanged at 165.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: Hue/Saturation and Color Balance keep the black ink

In a CMYK document Photoshop applies Hue/Saturation (not Colorize) and
Color Balance to C, M and Y as the complement of an RGB colour, and
leaves the black ink alone. On the photoshop corpus's own inks,
cmyk16 hue-saturation.psd follows this on every pixel within half a
level (cmyk8 within two), and color-balance within our RGB Color
Balance's own error. We applied both to the separated screen colour,
which also rewrote K.

- adjust::cmy_adjustment and apply_cmy run the RGB adjustment once per
  band on (1 - c, 1 - m, 1 - y).
- The ink compositor (InkOp::Cmy), the RGB compositor's CMYK branch and
  destructive Image > Adjustments (pixels::adjusted_cmy) use them. The
  GPU leaves these to the CPU in CMYK documents, as it does the other
  ink rules.
- Colorize separates its colour again, black included, so it keeps the
  screen-colour path.

cmyk8/16 oracles, bad pixels:
- hue-saturation: 100% -> 0.4-0.7%
- color-balance: 74% -> 25%

Neither passes yet. Half a level of cyan ink is three levels of red
through the profile at saturated cyan, and our RGB models leave that
much. The pass count stays at 165.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* 32-bit: legacy Brightness/Contrast, Channel Mixer, Photo Filter and B&W tint unclipped

In 32-bit documents Photoshop keeps these adjustments' results above 1
and below 0. On the photoshop corpus's rgb32/gray32 files:
- Legacy Brightness/Contrast pivots its contrast at 127 of 255 (8/16-bit:
  128) and is exact on every pixel.
- Channel Mixer cuts each source percentage to 1/1024 toward zero, counts
  255/512 of the constant and is exact on pure red, green, blue, black
  and white.
- Photo Filter works on the linear samples, negative results included.
- The Black & White tint is the Color blend mode without the clip at 1,
  as the blend mode is there; white tints to (1.05, 1.00, 0.87).

We clipped all four to 0..1. The GPU kernels follow suit under F_HDR
(the legacy pivot and the mixer's steps come from the planner), and the
HDR parity test covers them.

Photoshop oracles: rgb32 and gray32 brightness-contrast-legacy, rgb32
channel-mixer and black-white-tint pass (145 -> 149 of 258); floor
145 -> 149. rgb32 photo-filter improves (0.19 -> 0.035 max); the rest is
its colour (#3790).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Modern brightness: knee at output 126, fit out to -95 and +150

psd-tools' brightnesscontrast_rgb.psd masks four Brightness/Contrast
layers to their own columns. Read through the exact contrast curve, it
gives Photoshop's brightness at -95, -31, +23 and +150, well past the
+/-50 samples the first fit had. The +/-50 curve extrapolated badly
there: 22 levels off at -95 and 25 at +150.

Every setting puts the knee at about the same output level, not input.
The roll-off's end slope falls as 1/(1 + 0.084 b). With the knee at
126/255 and that end slope, the cubic Hermite fits -95, -50, -31, +23,
+25 and +50 within 1.4 levels. Past about +110 no such cubic stays
below white, so there the roll-off is 1 - (1 - y0)(1 - u)^alpha, with
the slope continuous at the knee. That gives +150 within 6 levels,
where every curve family tried bottoms out. Lowered curves are still
the inverse of raised ones.

The photoshop corpus's six brightness-contrast oracles still pass.
psd-tools brightnesscontrast_rgb goes from 0.13 to 0.020 max error and
_grayscale from 0.098 to 0.016. The new measurements are pinned in
modern_brightness_matches_photoshop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Levels: whole levels at every step and Photoshop's shadow toe

In 8 bits Photoshop rounds each of the three Levels steps to a whole
level (half up): the input-range stretch (already modelled), the
midtone gamma and the output range. A narrow output range therefore
merges neighbouring gamma levels: psd-tools levels_rgb maps R 43..48 to
58 through a 0.47 channel gamma and the master's 48..255, where the
unrounded curve gave 56..59 (3 levels off in blue).

The gamma above 1 starts along a toe a*u - b*u^q of slope a = 2^gamma
that joins the power curve with the same value and slope (q = 2.2,
fitted). With the rounding, that is exact on 1116 of the 1118 levels
of gamma 1.16, 1.22, 1.3, 1.78 and 2.0 oracles; the soft-min it replaces
missed 52. Gamma below 1 stays the plain power curve (0.67 and 0.7:
every level exact).

Oracles: psd-tools levels_rgb 0.0118 -> 0.0039 (PASS); photoshop
rgb8/stack-levels-curves-hue-posterize 0.2000 -> 0.0000 (PASS); rgb8 and
gray8 levels.psd 0.0039 -> 0.0000; rgb16/gray16 0.0039 -> 0.0020. Floors:
photoshop 145 -> 146, psd-tools 236 -> 238 (main is at 237).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Masks: feathers blur with exactly the feather's variance

A mask feather is a Gaussian with sigma = feather, which we approximate
with three box passes per axis. Whole-pixel boxes rounded the variance:
a 6 px feather blurred like 6.48 px and a 3 px one like 3.46 px, so
feathered edges were too soft by up to 4 levels against Photoshop
(psd-tools mask-parameters-no-real-channel.psd: a 6 px vector and 3 px
pixel feather).

Each pass is now an "extended box" (Gwosdek et al. 2011): weight 1 on
the whole radius and a fractional weight on the two samples beyond it,
so three passes have variance sigma^2 exactly. It stays O(n), reusing
the window's leaving sample for the low end weight (50 MP at a 1000 px
feather: 180 ms parallel, was 172).

psd-tools: mask-parameters-no-real-channel 0.0168 -> 0.0060 (PASS),
layer_mask_data.psd 26.9 % -> 3.9 % of pixels off (psb 25.9 % -> 1.8 %).
Corpus test 239 -> 240; floor 236 -> 240.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Lab: adjustment layers composite on the stored L, a and b

The compositor reads a Lab document's layers through display RGB, which
clips colours outside its gamut, so the adjustments Photoshop evaluates
on L, a and b (Invert, Posterize, Threshold, Brightness/Contrast, Levels
and Curves with Lab records) only saw the clipped colours: the photoshop
corpus's Lab oracles were up to 11 levels off on saturated colours.

compose::native_lab works a Lab stack of plain layers out on the stored
values instead, like the CMYK ink path: Normal mixes L, a and b
linearly, an opaque layer keeps them exactly, a layer mask scales the
mix, and adjustment layers run adjust::lab_stored_op on each pixel.
Stacks with such adjustments render for display this way; flattening a
plain Lab stack keeps its stored values (exports no longer clip).
Anything else (other blend modes, effects, other adjustments) keeps the
RGB compositor.

Photoshop oracles 145 -> 152: lab16 invert, posterize-4, levels, curves
and brightness-contrast-legacy; lab8 invert and posterize-4. lab8
levels and legacy B/C come within a level (their 8-bit rules are #5143
and #5132). psd-tools and io unchanged; every round trip unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Threshold: split on Photoshop's luminosity of whole samples

Photoshop's Threshold splits on the luminosity 0.30 R + 0.59 G + 0.11 B
(the blend modes' lum, as Gradient Map uses), not the Rec. 601 grey,
taken over the document's whole sample values:

- 8 bits: 30 R + 59 G + 11 B > 100 level - 50, i.e. the luminosity
  rounded to a level with halves down reaches the level;
- 16 bits: 30 R + 59 G + 11 B >= 100 x the level in 16 bits
  (round(level x 32768 / 255): mid grey 16448 is level 128);
- 32 bits: the luminosity reaches the level.

Exact on every pixel of psd-tools threshold_rgb (36432 px; Rec. 601 split
28 the other way), threshold_16bits_rgb (100) and threshold_16bits_
grayscale, and the photoshop corpus's rgb16 threshold-128. The sums are
exact in f32, on the CPU and in the GPU kernel, so ties (grey exactly on
the level) split the same way on both.

psd-tools: threshold_rgb and threshold_16bits_rgb pass; corpus test
239 -> 241, floor 236 -> 241.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Posterize: 16-bit documents bin the 16-bit sample, as Photoshop does

At 16 bits Photoshop doesn't round to 8-bit levels before binning. It
bins the 16-bit sample, floor(v16 * n / 32768), and lands on 8-bit levels
through a 16-bit step: floor(b * 32768 / (n - 1)), converted with
floor((o * 255 + 16384) / 32768). So the middle of 3 levels is 128 where
8 bits give 127, while 42.5 and 25.5 stay 42 and 25.

Exact on every sample of psd-tools posterize_16bits_rgb (levels 3, 7,
13, 21) and posterize_16bits_grayscale (2, 6, 9, 11); the 8-bit rule
missed up to half the range at bin edges. The same rule applies to
CMYK and Lab channels at 16 bits: on the stored inks (#4945's native
path) psd-tools posterize_16bits_cmyk goes from 4.26 % to 0.01 % of
pixels off. 8-bit Posterize is unchanged.

The GPU kernel runs the same rule; 16-bit layers reach it as half
floats, so a sample within their precision of a bin edge can land in
the neighbouring bin there (the CPU, which exports, is exact).

psd-tools 239 -> 241; floor 236 -> 241.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: Posterize works on the stored values (1 - ink)

Photoshop posterizes a CMYK channel's stored value, 1 - ink, not the
ink: with levels whose steps are uneven (3, 7, 13, 21) the two differ,
e.g. 3 levels take an ink of 85 to 128, where posterizing the ink drops
it to none. psd-tools posterize_cmyk.psd goes from 13.8 % of pixels off
to exact; psd-tools 241 -> 242, floor 242.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Groups: a pass-through clipping base with an adjustment renders isolated

A pass-through group composites its children straight into the
backdrop, so an adjustment layer inside reaches the layers beneath.
When the group is the base of a clipping group and holds an adjustment
layer, Photoshop renders it isolated instead: in psd-tools
passthrough_clipping_mask_adjustment an Exposure in such a group leaves
the layers beneath alone (we darkened them: half the image 170 levels
off). The same group with a Linear Dodge child and no adjustment keeps
reaching the backdrop (passthrough_clipping_mask_blendmode), and so do
clipping-mask3/4/5, so the rule is the adjustment, not the clipping
alone (isolating every pass-through clipping base broke those two).

CPU compositor and GPU plan alike. psd-tools 239 -> 240; floor 240.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Raise corpus floors to the results of the landed adjustment fixes

Photoshop-authored 165 -> 185 of 258, io 146 -> 148 of 170, psd-tools 242 -> 249 of 309,
measured with the CMYK, Lab, 32-bit, Levels, Threshold, Posterize, feather and
pass-through PRs merged together.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
2026-10-14 14:12:06 -04:00
92c7922230 CMYK: Brightness/Contrast curves each ink, as Photoshop does (#4930)
* Modern Brightness/Contrast: Photoshop's brightness curve

The modern brightness curve was a line rolled off by a v^P term. It sat
up to 4 levels off Photoshop's in the highlights, and up to 2.3 levels
off for lowered brightness.

The curve is refit to the Photoshop ground truth we have:
- the ±50 samples from 4759d12b;
- the photoshop corpus's brightness +25 / contrast +30 files,
  inverted through the (exact) contrast curve.

Raised, it is the line s*x (s = 1.375^(b/50)) up to a knee at 80/255,
then a cubic Hermite to white with end slope s^-6.6. Lowered, it is the
exact inverse of the curve raised by as much (the -50 samples confirm
this to within a level). Every measured point is within about a level.
For strong values the knee moves down so the curve stays monotone
across -150..150.

Brightness then contrast are evaluated through one 4096-entry table,
built in 55 us. The GPU uses that same table through the Levels/Curves
kernel instead of rebuilding the curves in WGSL, so GPU and CPU agree
by construction.

Photoshop oracles: rgb8/16/32 and gray8/16/32 brightness-contrast now
pass (145 -> 151 of 258). The floor goes 133 -> 151.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: Brightness/Contrast curves each ink, as Photoshop does

Photoshop applies Brightness/Contrast in a CMYK document to each ink's
stored value, 1 - ink, black included. Both the modern and the legacy
curve do this; the cmyk8 brightness-contrast(-legacy) oracles match it
within a level on every pixel of the files' own inks. Raising
brightness takes ink away. We applied it to the screen colour instead.

- cmyk_channel_adjustment gains Brightness/Contrast. apply_in builds
  the channel curve once (brightness_contrast_lut) and runs each
  separated ink through it (ink_through).
- Destructive Image > Adjustments on a CMYK layer curves the stored
  inks directly, so it is exact; a selection mixes them.
  adjusted_channels now takes the per-pixel operation, and works out
  luma only for CMYK Threshold, which compares it.
- The GPU leaves CMYK Brightness/Contrast to the CPU, like the other
  ink rules.

cmyk8/16 brightness-contrast oracles, bad pixels:
- modern: 72% -> 48-57%, max error 0.19 -> 0.09
- legacy: 71% -> 51-53%

The rest is our separation of the RGB composite, not the rule.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK Threshold compares the inks' own luma, as Photoshop does

Photoshop's CMYK Threshold splits on the Rec. 601 luma of the inks' plain
complement, (1 - c)(1 - k) and so on, whatever the document's profile.
On the files' own inks this puts every pixel of cmyk8 and cmyk16
threshold-128.psd on the right side of level 128. The profile's RGB luma
missed 100.

stored_channels works the luma out from the inks itself (ink_luma), so it
no longer takes one; the engine's stored-channel path no longer converts
each pixel to RGB at all. Through the separated RGB composite the cmyk
threshold oracles drop from 1.6% to 0.2% bad pixels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK legacy Brightness/Contrast pivots at 128 in ink

Photoshop's legacy contrast pivots at level 128 of the ink, which is 127
of 255 of the stored value (1 - ink) that the curve runs on, not 128 as
in RGB. On Photoshop's own 16-bit inks (cmyk16
brightness-contrast-legacy.psd) ours sat a constant 0.43 of a level
above. That is exactly the one-level pivot shift times contrast +30's
slope minus one; with the pivot moved, the inks match within 0.01.

brightness_contrast_lut is now ink_brightness_contrast_lut, since its
legacy curve is the CMYK one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* 32-bit: legacy Brightness/Contrast, Channel Mixer, Photo Filter and B&W tint unclipped

In 32-bit documents Photoshop keeps these adjustments' results above 1
and below 0. On the photoshop corpus's rgb32/gray32 files:
- Legacy Brightness/Contrast pivots its contrast at 127 of 255 (8/16-bit:
  128) and is exact on every pixel.
- Channel Mixer cuts each source percentage to 1/1024 toward zero, counts
  255/512 of the constant and is exact on pure red, green, blue, black
  and white.
- Photo Filter works on the linear samples, negative results included.
- The Black & White tint is the Color blend mode without the clip at 1,
  as the blend mode is there; white tints to (1.05, 1.00, 0.87).

We clipped all four to 0..1. The GPU kernels follow suit under F_HDR
(the legacy pivot and the mixer's steps come from the planner), and the
HDR parity test covers them.

Photoshop oracles: rgb32 and gray32 brightness-contrast-legacy, rgb32
channel-mixer and black-white-tint pass (145 -> 149 of 258); floor
145 -> 149. rgb32 photo-filter improves (0.19 -> 0.035 max); the rest is
its colour (#3790).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Modern brightness: knee at output 126, fit out to -95 and +150

psd-tools' brightnesscontrast_rgb.psd masks four Brightness/Contrast
layers to their own columns. Read through the exact contrast curve, it
gives Photoshop's brightness at -95, -31, +23 and +150, well past the
+/-50 samples the first fit had. The +/-50 curve extrapolated badly
there: 22 levels off at -95 and 25 at +150.

Every setting puts the knee at about the same output level, not input.
The roll-off's end slope falls as 1/(1 + 0.084 b). With the knee at
126/255 and that end slope, the cubic Hermite fits -95, -50, -31, +23,
+25 and +50 within 1.4 levels. Past about +110 no such cubic stays
below white, so there the roll-off is 1 - (1 - y0)(1 - u)^alpha, with
the slope continuous at the knee. That gives +150 within 6 levels,
where every curve family tried bottoms out. Lowered curves are still
the inverse of raised ones.

The photoshop corpus's six brightness-contrast oracles still pass.
psd-tools brightnesscontrast_rgb goes from 0.13 to 0.020 max error and
_grayscale from 0.098 to 0.016. The new measurements are pinned in
modern_brightness_matches_photoshop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Levels: whole levels at every step and Photoshop's shadow toe

In 8 bits Photoshop rounds each of the three Levels steps to a whole
level (half up): the input-range stretch (already modelled), the
midtone gamma and the output range. A narrow output range therefore
merges neighbouring gamma levels: psd-tools levels_rgb maps R 43..48 to
58 through a 0.47 channel gamma and the master's 48..255, where the
unrounded curve gave 56..59 (3 levels off in blue).

The gamma above 1 starts along a toe a*u - b*u^q of slope a = 2^gamma
that joins the power curve with the same value and slope (q = 2.2,
fitted). With the rounding, that is exact on 1116 of the 1118 levels
of gamma 1.16, 1.22, 1.3, 1.78 and 2.0 oracles; the soft-min it replaces
missed 52. Gamma below 1 stays the plain power curve (0.67 and 0.7:
every level exact).

Oracles: psd-tools levels_rgb 0.0118 -> 0.0039 (PASS); photoshop
rgb8/stack-levels-curves-hue-posterize 0.2000 -> 0.0000 (PASS); rgb8 and
gray8 levels.psd 0.0039 -> 0.0000; rgb16/gray16 0.0039 -> 0.0020. Floors:
photoshop 145 -> 146, psd-tools 236 -> 238 (main is at 237).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Masks: feathers blur with exactly the feather's variance

A mask feather is a Gaussian with sigma = feather, which we approximate
with three box passes per axis. Whole-pixel boxes rounded the variance:
a 6 px feather blurred like 6.48 px and a 3 px one like 3.46 px, so
feathered edges were too soft by up to 4 levels against Photoshop
(psd-tools mask-parameters-no-real-channel.psd: a 6 px vector and 3 px
pixel feather).

Each pass is now an "extended box" (Gwosdek et al. 2011): weight 1 on
the whole radius and a fractional weight on the two samples beyond it,
so three passes have variance sigma^2 exactly. It stays O(n), reusing
the window's leaving sample for the low end weight (50 MP at a 1000 px
feather: 180 ms parallel, was 172).

psd-tools: mask-parameters-no-real-channel 0.0168 -> 0.0060 (PASS),
layer_mask_data.psd 26.9 % -> 3.9 % of pixels off (psb 25.9 % -> 1.8 %).
Corpus test 239 -> 240; floor 236 -> 240.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Lab: adjustment layers composite on the stored L, a and b

The compositor reads a Lab document's layers through display RGB, which
clips colours outside its gamut, so the adjustments Photoshop evaluates
on L, a and b (Invert, Posterize, Threshold, Brightness/Contrast, Levels
and Curves with Lab records) only saw the clipped colours: the photoshop
corpus's Lab oracles were up to 11 levels off on saturated colours.

compose::native_lab works a Lab stack of plain layers out on the stored
values instead, like the CMYK ink path: Normal mixes L, a and b
linearly, an opaque layer keeps them exactly, a layer mask scales the
mix, and adjustment layers run adjust::lab_stored_op on each pixel.
Stacks with such adjustments render for display this way; flattening a
plain Lab stack keeps its stored values (exports no longer clip).
Anything else (other blend modes, effects, other adjustments) keeps the
RGB compositor.

Photoshop oracles 145 -> 152: lab16 invert, posterize-4, levels, curves
and brightness-contrast-legacy; lab8 invert and posterize-4. lab8
levels and legacy B/C come within a level (their 8-bit rules are #5143
and #5132). psd-tools and io unchanged; every round trip unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Threshold: split on Photoshop's luminosity of whole samples

Photoshop's Threshold splits on the luminosity 0.30 R + 0.59 G + 0.11 B
(the blend modes' lum, as Gradient Map uses), not the Rec. 601 grey,
taken over the document's whole sample values:

- 8 bits: 30 R + 59 G + 11 B > 100 level - 50, i.e. the luminosity
  rounded to a level with halves down reaches the level;
- 16 bits: 30 R + 59 G + 11 B >= 100 x the level in 16 bits
  (round(level x 32768 / 255): mid grey 16448 is level 128);
- 32 bits: the luminosity reaches the level.

Exact on every pixel of psd-tools threshold_rgb (36432 px; Rec. 601 split
28 the other way), threshold_16bits_rgb (100) and threshold_16bits_
grayscale, and the photoshop corpus's rgb16 threshold-128. The sums are
exact in f32, on the CPU and in the GPU kernel, so ties (grey exactly on
the level) split the same way on both.

psd-tools: threshold_rgb and threshold_16bits_rgb pass; corpus test
239 -> 241, floor 236 -> 241.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Posterize: 16-bit documents bin the 16-bit sample, as Photoshop does

At 16 bits Photoshop doesn't round to 8-bit levels before binning. It
bins the 16-bit sample, floor(v16 * n / 32768), and lands on 8-bit levels
through a 16-bit step: floor(b * 32768 / (n - 1)), converted with
floor((o * 255 + 16384) / 32768). So the middle of 3 levels is 128 where
8 bits give 127, while 42.5 and 25.5 stay 42 and 25.

Exact on every sample of psd-tools posterize_16bits_rgb (levels 3, 7,
13, 21) and posterize_16bits_grayscale (2, 6, 9, 11); the 8-bit rule
missed up to half the range at bin edges. The same rule applies to
CMYK and Lab channels at 16 bits: on the stored inks (#4945's native
path) psd-tools posterize_16bits_cmyk goes from 4.26 % to 0.01 % of
pixels off. 8-bit Posterize is unchanged.

The GPU kernel runs the same rule; 16-bit layers reach it as half
floats, so a sample within their precision of a bin edge can land in
the neighbouring bin there (the CPU, which exports, is exact).

psd-tools 239 -> 241; floor 236 -> 241.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Groups: a pass-through clipping base with an adjustment renders isolated

A pass-through group composites its children straight into the
backdrop, so an adjustment layer inside reaches the layers beneath.
When the group is the base of a clipping group and holds an adjustment
layer, Photoshop renders it isolated instead: in psd-tools
passthrough_clipping_mask_adjustment an Exposure in such a group leaves
the layers beneath alone (we darkened them: half the image 170 levels
off). The same group with a Linear Dodge child and no adjustment keeps
reaching the backdrop (passthrough_clipping_mask_blendmode), and so do
clipping-mask3/4/5, so the rule is the adjustment, not the clipping
alone (isolating every pass-through clipping base broke those two).

CPU compositor and GPU plan alike. psd-tools 239 -> 240; floor 240.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
2026-10-14 14:11:19 -04:00
becc27ac1c CMYK: Invert, Posterize and Threshold on the inks; 16-bit Lab Invert keeps greys neutral (#3930)
* Lab and CMYK: Invert, Posterize and Threshold work on the document's channels

Photoshop applies these to each stored channel, not to RGB:
- Lab: Invert and Posterize work on L, a and b, and Threshold cuts on L
  to a neutral black or white.
- CMYK: Invert and Posterize work on each ink, black included, so
  paper inverts to 400% ink. Threshold gives paper or 100% black ink.

Adjustment layers now do the same:
- compose::adjust::apply_mode goes through the document's Lab or CMYK
  channels.
- The GPU falls back to the CPU for these, as it already does for
  Lab/CMYK Levels and Curves.
- The destructive Image > Adjustments path works on the stored samples
  directly, so it is exact.

Photoshop oracles (lab/cmyk 8 and 16 bit), bad pixels before -> after:
- lab threshold: PASS (was 12%)
- lab invert: 72-99% -> 1%
- lab posterize: 89% -> 0.1%
- cmyk invert: 77% -> 10%
- cmyk posterize: 71% -> 9%
- cmyk threshold: 37% -> 1.6%

Floor 133 -> 139 (137 already passed on main).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* CMYK: Invert, Posterize and Threshold on the inks; 16-bit Lab Invert keeps greys neutral

Builds on main's adjust::apply_in (#4038):
- apply_in's mode dispatch gains CMYK. Invert and Posterize work on each
  ink, black included, so paper inverts to 400% ink. Threshold gives
  paper or 100% black ink alone. cmyk_channel_adjustment says which
  adjustments do this.
- Lab Invert mirrors a and b around neutral at 16 bits; 8-bit bytes
  still become 255 - v. stored_channels holds both rules, and
  apply_lab uses it.
- Destructive Image > Adjustments on a Lab or CMYK layer works on its
  stored channels directly, so it is exact; a selection mixes the
  stored values.
- The GPU leaves CMYK Invert, Posterize and Threshold to the CPU.

Photoshop oracles, bad pixels:
- cmyk invert: 77% -> 10%
- cmyk posterize: 71% -> 9%
- cmyk threshold: 37% -> 1.6%
- lab16 invert: 52% -> 1.2%

The count stays at 145/258, which main already passes, so the floor
goes 133 -> 145.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
2026-10-13 01:38:52 -04:00
SckraTandClaude 1e9f1ae486 perf(engine): read selection coverage per row when mixing edits back (#4424)
Destructive adjustments (pixels::adjusted) and the RGBA filter helper (adjust_cmds
process_surface) each had the same loop mixing the edited pixels back over the original by
selection coverage, looking the selection's tile up for every pixel (sample_channel, a
BTreeMap lookup per pixel). They now share pixels::mix_through_selection, which reads the
coverage one row at a time with sample_row_strided: one tile lookup per tile per row, and a
row-sized buffer.

Results are unchanged: a new test compares the helper with the per-pixel sample_channel mix,
bit for bit, for 8-bit, 8-bit-with-alpha and 32-bit selections over 8- and 16-bit layers,
across tile edges and untouched (default) selection tiles.


Claude-Session: https://claude.ai/code/session_01QUda3K786uop8kvEQoUjSf

Co-authored-by: Claude <noreply@anthropic.com>
2026-10-12 19:55:21 -04:00
Brandon ThomasandClaude Opus 5.5 27f56eb762 feat(compose): Lab documents evaluate Invert, Posterize, Threshold, Brightness/Contrast and Gradient Map on L, a, b (#4038)
In Lab documents Photoshop evaluates these adjustments on the Lab channels,
not on the screen RGB colour:

- Invert and Posterize act on L, a and b alike (normalised L/100,
  (a+128)/255, (b+128)/255; Invert is n -> 1 - n).
- Brightness/Contrast (modern and legacy) applies its tone curve to L only;
  a and b are unchanged.
- Threshold splits on L alone and outputs neutral black or white.
- Gradient Map is driven by L (Reverse uses 1 - L).

Adjustment layers (CPU compositor) and destructive Image > Adjustments both
go through the new `adjust::apply_in`; the GPU compositor defers these
adjustments to the CPU in Lab documents. Levels and Curves keep their Lab
records; other adjustments stay on the screen colour.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-12 06:20:44 -04:00
4030096482 perf: Edit > Clear works tile by tile on large selections (#3463) (#3482)
Clear (and the background-colour fill it does on a Background layer)
read the whole selection bounds into one float buffer, looked the
selection up in its tile map once per pixel and wrote every tile back,
single-threaded. On an 8000x6000 layer that took about 2 s (3 s on the
Background). It now edits the encoded tiles in parallel, drops fully
cleared tiles, shares one solid tile for fully covered opaque fills and
copies a tile only when a pixel in it changes. Results match the old
pass exactly; 20-110 ms on the same documents.

Fixes #3463

Co-authored-by: Fabio Lussi <198260595+itrycodinganditsbad@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-11 23:29:25 -04:00
5e0e9c595b Speed up large group merges (#1561) (#2664)
* Speed up large layer group merges

* Merges: bound by composite_bounds so layer effects outside the pixels are kept

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-10 17:28:53 -04:00
kayrockscreenprintingandClaude Opus 5.5 54ff207004 Image › Adjustments: apply per tile in parallel (#1800)
adjust_surface now takes the layer's tiles and adjusts each one on its own rayon task, so a large layer needs one tile's buffers per thread instead of four full-layer copies. The result is bit-identical to the single pass for every adjustment kind, colour model and depth, with and without a soft selection (tiled_adjustment_matches_one_pass_over_the_content). Adds an invert scenario to large_image_bench.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-09 13:06:46 -04:00