Brightness, contrast, saturation, digital vibrance, gamma, color temperature, hue, blue light reduction and black-equalizer shadow detail — for Windows, in one tray app. Works on any GPU, with or without DDC/CI, on HDR displays, and inside exclusive-fullscreen games. Profiles switch themselves by foreground application or time of day, and everything is scriptable from the command line.

Written in pure C++ with Win32 — no framework, no runtime, no dependencies. A 1.6 MB executable using 3.6 MB of RAM and 0% CPU at idle. The zero is literal: there is no polling loop anywhere. The program sleeps, and Windows wakes it through SetWinEventHook when the foreground window changes.

Download the latest release · project page

The interface is in English, and in Portuguese on a machine set to Portuguese. See Other languages.

Install

Windows 10 or 11, 64-bit. Nothing else — no .NET, no Visual C++ redistributable. Neither option asks for administrator rights.

Important

The green Code → Download ZIP button at the top of this page gives you the source code, not the program. The program is on the Releases page.

With the installer — the usual choice.

1. Download zdisplay-setup-<version>-x64.exe from the latest release.
2. Run it. Windows SmartScreen will warn, because the file is not yet code-signed: click More info, then Run anyway. See the FAQ for why, and verify the SHA-256 first if you prefer.
3. It installs into %LOCALAPPDATA%\Programs\Zdisplay, adds a Start menu shortcut, registers itself under Installed apps, and includes an uninstaller.

Portable, without installing — for a USB stick, or to try it and delete it.

1. Download zdisplay-<version>-x64-portable.zip.
2. Extract it anywhere.
3. Run zdisplay.exe.

Just the executable — zdisplay-<version>-x64.exe is also attached on its own. It runs as it is; the only difference is that settings go to %APPDATA%\Zdisplay like any normal program.

That single file is the whole program either way. What makes a copy portable is an empty file named zdisplay-portable.txt beside it, and the archive above simply ships that file already created — worth having, because Windows hides known extensions by default, so creating it by hand usually produces zdisplay-portable.txt.txt, which Zdisplay ignores without complaining.

With a package manager — planned, not yet available. The winget manifests are prepared and awaiting submission.

Zdisplay lives in the system tray. Double-click its icon to open the settings; middle-click pauses and restores the screen instantly. If anything goes wrong, Ctrl+Alt+Shift+K restores the display from anywhere in Windows.

Contents

Why it exists — the black equalizer no other tool has · what the alternatives leave out · how it works on any PC

What it does — blue light reduction · the Vision tab · shadow detail, in depth

Using it — building · running and scripting · safeguards · tests

Knowing the limits — the Windows gamma limit · honest caveats · questions people actually ask

The project — security · contributing · source layout · other languages · license

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Black equalizer in software — the part no other tool does

Shadow detail on any monitor, without the panel's own menu.

Gaming monitors sell this as Black eQualizer, Shadow Boost or Dark Boost, and it only exists in the panel's own menu — if you paid for a panel that has it. It raises near-black detail so you can see into the unlit corner of a map or the dim room in a film.

Every implementation has the same complaint: push it up and the shadows flatten into one grey, and the picture looks washed out. That happens because raising the black floor also flattens the slope near black, so neighbouring dark tones collapse into the same value.

Zdisplay splits the job into two sliders. Shadows raises the floor; Clarity restores the slope the lift flattens. Measured across the 32 darkest tones, how many stay distinct from one another:

Setting	Distinct tones	Tone 128 (midtone)	Tone 255 (white)
neutral	32 / 32	128	255
Shadows 100, no Clarity	20 / 32	—	—
Shadows 78 + Clarity 65	27 / 32	129	255

The midtone moves by one point and white does not move at all. And because it goes through the gamma ramp rather than an overlay, it works inside exclusive-fullscreen games, with no frame cost and without showing up in screenshots.

Full explanation, with the curve and its limits →

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What Twinkle Tray, f.lux and vibranceGUI leave out

Each of those is good at its own job. The problem is that their jobs are narrower than the screen is, so covering everything means running three of them — and then they fight each other over the same Windows gamma ramp, where the last writer wins:

Program	Covers	Stops at
vibranceGUI	NVIDIA vibrance per game	brightness, contrast, gamma, Intel
LightBulb / f.lux	color temperature	saturation, monitor hardware
Gammy	adaptive brightness	saturation, per-app profiles
Twinkle Tray	DDC/CI brightness (excellent, but Electron: 100–250 MB of RAM)	color
Monitorian	lightweight DDC/CI brightness	color
DimScreen	dimming below the panel minimum	everything else

Zdisplay brings the seven functions into a single program, resolves the conflicts between them, and picks the best available path on each machine by itself. Three things in that table have no entry at all — shadow detail on any monitor, saturation on Intel graphics, and brightness on an HDR display — because no tool in this category does them.

Coming from another tool

• From Twinkle Tray or Monitorian — you keep DDC/CI hardware brightness and gain color, per-app profiles and a 1.6 MB native binary instead of 100–250 MB of Electron. Zdisplay also talks VCP directly to panels whose capability string Windows rejects, which is where those tools go quiet.
• From vibranceGUI — same per-game vibrance on NVIDIA and AMD, plus a universal color matrix that gives saturation on Intel integrated graphics, which has no vendor API and is therefore unsupported there. Zdisplay also checks which adapter actually drives each display, so on a hybrid laptop the vendor call is not silently applied to a screen it does not control.
• From f.lux or LightBulb — the same sunset-driven warming, layered over profiles rather than fighting them, with a separate blue-reduction slider so you can cut blue without moving the whole white point.
• From Gammy — shadow detail is done through the gamma ramp instead of screen captures, so it costs no CPU and works in exclusive fullscreen.
• From a monitor's Black eQualizer / Shadow Boost — the same effect on any panel, with a second slider that stops the shadows collapsing into one grey.

Works on any PC

At startup Zdisplay detects what the machine supports and assembles a backend stack with automatic fallback. Nothing is required: if the vendor GPU is not there, the universal path takes over.

Backend	Controls	Works on	Limits
Gamma ramp (GDI)	brightness, contrast, gamma, temperature, white balance, blue light reduction	any GPU, per monitor	works even in exclusive-fullscreen games; Windows restricts the range (see below)
Color matrix (Magnification API)	saturation, hue, inversion	any PC, integrated graphics included	global effect (not per monitor); does not reach exclusive fullscreen
NVIDIA (NVAPI)	vibrance (DVC), hue	NVIDIA only	loaded at runtime
AMD (ADL)	saturation, hue	AMD only	loaded at runtime
DDC/CI	brightness, contrast, RGB gain and saturation in the monitor hardware, plus input, color preset and power	compatible external monitors	slow; queued with a minimum interval to spare the EEPROM
SDR white level	brightness on an HDR-enabled display, where the ramp does not apply	Windows 10 1803+, per monitor	governs SDR content; HDR video and games keep their own brightness
Backlight (WMI)	physical brightness of the internal panel	laptops and all-in-ones	uses the steps the panel declares; matches the WMI instance to the right monitor
Overlay	dimming below the panel minimum	any PC	washes out contrast; appears in screenshots

See what your machine supports with zdisplay.exe --diag or in the Diagnostics tab (Diagnóstico).

The tab lists, for each monitor, what handles what — and, when a control does not work there, why. It answers the question that actually comes up: "why does this slider do nothing on this screen?"

AOC FTV (DISPLAY1)
    brightness, contrast, gamma, temperature, shadows: gamma ramp
    saturation, vibrance, hue: AMD (ADL) + color matrix
    physical brightness: unavailable (this monitor did not answer DDC/CI)

Diagnostics are always in English, whatever the interface language is: they exist to be pasted into a problem report and read by whoever maintains the program.

The tab shows the same thing in full — every backend marked [ok] or [--] with the reason, then each monitor with its EDID, its gamut, which adapter drives it, and which backend owns each adjustment:

Generic, unbranded monitors with poor firmware

The Windows high-level API (GetMonitorBrightness / SetMonitorBrightness) validates the monitor's capability string before talking to it. Cheap panels often report that string truncated, malformed or missing — and the API then refuses, even when the monitor would have obeyed. Zdisplay tries the high-level path first and, when it refuses, speaks VCP directly to the panel. A monitor that does not respond even then is shown as "unsupported" rather than vanishing from the list.

Hardware RGB gain (VCP 0x16 / 0x18 / 0x1A) is probed by reading the register itself, not by asking for capabilities. It becomes the color temperature path when the gamma ramp does not apply — which is the case on an HDR-enabled display, where SetDeviceGammaRamp returns success without changing a single pixel.

Monitor identity

Each monitor's key comes from its EDID (manufacturer + model + serial number), not from the device path. The path carries the number of the port the cable is plugged into, so moving to a different output on the card would make that monitor's own settings disappear. Configurations written in the old format are migrated automatically.

The EDID also provides the panel's real name instead of "Generic PnP Monitor", and the gamut coordinates — which is what explains a cheap wide-gamut monitor oversaturating without anything being wrong in Zdisplay.

Two graphics adapters in one machine

On a hybrid laptop the display is usually driven by the Intel adapter even when an NVIDIA one is present. Zdisplay determines which adapter drives each display (DISPLAYCONFIG_ADAPTER_NAME) and uses the vendor path only where it actually applies. Otherwise the vendor API accepts the command and reports success without changing anything — a silent failure, the worst kind.

Intel does not expose driver-level vibrance the way NVIDIA and AMD do; on those machines saturation goes through the universal color matrix, and the diagnostics say so instead of letting the slider look broken.

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Blue light reduction

A slider in the Settings tab (Ajustes), stored in each profile like any other adjustment. It exists separately from color temperature on purpose: temperature shifts the whole white point, so someone who only wants to cut blue ends up choosing a Kelvin value that also moves red — and then cannot say how much blue is left. Here the slider's number answers how much blue am I cutting directly.

It cuts blue and, more gently, green; red does not move. At maximum, 15% of blue remains — zeroing the channel would erase every distinction between the blue tones in the image, and the light floor would have to undo the adjustment immediately afterwards.

The slider counts toward the light floor like every other field: no combination of blue reduction, brightness and temperature can break through it, and that is tested.

It is the manual, per-profile version of what the Vision tab (Visão) does automatically by the clock — the two coexist, and the vision layer never undoes what the profile asked for.

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The Vision tab — eye comfort, in one switch

One switch and four numbers. The screen warms up on its own as the sun sets and returns to normal in the morning, on top of any profile — no need to create a profile or a schedule rule for it.

Field	What it does
Day temperature	6500 K is neutral white.
Night temperature	3400 K is incandescent-lamp color. The lower it is, the less blue reaches your eyes.
Night brightness	% of what the profile asks for. It matters as much as color: what tires the eyes is the screen being much brighter than the room.
Transition smoothness	Minutes. The change happens gradually around the time, half before and half after. An hour is already imperceptible.
Night / day begins	A clock time (22:00) or the sun itself: sunset, sunrise, sunset-30, sunrise+45.
Eye break	Every N minutes, a discreet tray reminder to look at something about 6 metres away for 20 seconds.

The layer never works against what you chose: if the active profile already asks for something warmer or darker than the night target, the profile wins. It only pulls toward comfort.

The preview buttons show the result while you hold them — choosing a night temperature without seeing it would be guesswork.

On what actually helps: reducing blue at night has evidence for sleep, not for eye strain. What the clinical literature actually recommends against screen fatigue is the 20-20-20 break — which is why it is here, and why the night brightness field exists: the difference between the screen and the room matters more than the color.

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Shadow detail (black equalizer)

Two sliders in the Settings tab for the problem of seeing what is in the dark — the unlit corner of the map, the dim room in a film — without washing out the rest of the image. It is what gaming monitors sell as Black eQualizer or Shadow Boost, done in software and on any monitor.

Slider	What it does
Shadows (0–100)	raises the black floor with a weight that dies out before the midtones
Clarity (0–100)	pushes near-black tones apart from each other, restoring the detail the lift would flatten

Why two and not one. Raising brightness or gamma lightens the entire image: the dark appears, but the midtones lose body and the highlights blow out. Restricting the effect to the low end of the curve solves that — except that raising the floor flattens the slope near black, and neighbouring tones collapse into the same value. The detail disappears exactly where you went looking for it. The second slider restores that slope.

Measuring across the 32 darkest tones, how many remain distinct from one another:

Setting	Distinct tones	Tone 0 becomes
neutral	32 / 32	0
Shadows 100 alone	20 / 32	40
Shadows 100 + Clarity 100	29 / 32	40
Shadows 78 + Clarity 65	27 / 32	31

And what happens to the rest of the image at Shadows 78 + Clarity 65:

Input tone	4	10	40	80	128	180	220	255
Output tone	35	41	64	89	129	180	220	255

Tone 10 — invisible in practice — becomes 41. Tone 128 moves by one point. From 180 upward nothing changes: whites, sky and interface stay exactly where they were.

Because all of this goes through the gamma ramp, it also applies inside exclusive-fullscreen games, with no overlay, no CPU cost, and without appearing in screenshots.

The built-in Competitivo profile ships with Shadows 78 / Clarity 65, and the Jogo profile gets a light dose (40 / 30).

What these sliders are not

• They are not edge sharpening. Real sharpening compares each pixel with its neighbours, and the gamma ramp is a 256-entry table that cannot see any neighbourhood at all — only the tone. Doing that would require capturing and reprocessing the screen frame by frame, which costs GPU time, adds latency and does not work in exclusive fullscreen. What Clarity does is low-tone contrast, which is what actually brings dark detail back.
• Dark colors lose a little saturation. The table is per channel and treats each one without knowing the others, so adding the same floor to R, G and B brings the three closer together — and closer means washed out. If it bothers you, compensate with +5 to +10 on Saturation.
• The strongest setting still merges 3 tones out of 32, because of the 8 bits in the signal. That is the price of stretching the low end of the curve; it cannot be reduced to zero in a tone table.

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Building

All you need is a C++ compiler (MinGW-w64). If you have none, the script downloads a portable one itself — no installation, no administrator rights.

build.bat

Or, with make on your PATH:

make

The icon is drawn by the program itself (zdisplay.exe --make-icon) — there is no dependency on any graphics tool.

Building the installer

build.bat setup

The result is zdisplay-setup.exe, a self-contained graphical installer. It installs per user in %LOCALAPPDATA%\Programs\Zdisplay, creates the Start menu shortcut, registers Zdisplay in Installed apps and includes the uninstaller. It never asks for administrator rights. The embedded executable is validated by CRC-32, SHA-256 and PE x64 structure before a single file is written.

Using it

zdisplay.exe

Double-click the tray icon to open the settings; middle-click pauses and restores the screen immediately.

The monitor's own colour

Monitor colour (RGB gain)…, at the bottom of the Monitor hardware section on the Adjustments tab, opens the panel's own colour registers over DDC/CI: the RGB gain and, where the panel offers it, its colour saturation. They are stored in the profile like the physical brightness is, they cost no tonal range because nothing goes through the gamma ramp, and unchecking a group gives the monitor back the values it had before Zdisplay wrote to them.

Each group appears only on a monitor that answered those registers, and nearly every panel accepts a gain write only while its colour preset is the user one — set that preset first, on the monitor itself or under Monitor commands.

Command line

With Zdisplay already running, any invocation becomes a command to the running instance — useful for scripts, Stream Deck, AutoHotkey or Windows shortcuts.

zdisplay.exe --profile "Jogo"      # activate a profile (built-in name: "Game")
zdisplay.exe --brightness 70       # software brightness (10..150)
zdisplay.exe --saturation 130      # saturation (0..200)
zdisplay.exe --vibrance 60         # GPU vibrance (0..100)
zdisplay.exe --temperature 3400    # color temperature in Kelvin
zdisplay.exe --shadows 78          # raise only the dark tones (0..100)
zdisplay.exe --clarity 65          # shadow detail (0..100)
zdisplay.exe --hwbrightness 40     # monitor hardware brightness (DDC/CI)
zdisplay.exe --dim 25              # extra dimming via overlay
zdisplay.exe --auto                # back to automatic mode
zdisplay.exe --toggle              # pause / resume
zdisplay.exe --reset               # return the screen to its original state
zdisplay.exe --panic               # EMERGENCY: restore the screen and pause
zdisplay.exe --status              # print the current state
zdisplay.exe --diag                # print the detected backends
zdisplay.exe --list                # list the profiles
zdisplay.exe --aba 5               # open on a tab: 0 Settings, 1 Vision,
                                   #   2 Profiles, 3 Automation, 4 System,
                                   #   5 Diagnostics
zdisplay.exe --quit

The commands that set a value (--brightness, --saturation, …) change the profile's global value. Monitors with their own override keep what you configured for them — the response tells you how many were left out. To change a specific monitor, use the window.

Called from a terminal, it writes the response to the terminal; outside one, it shows a dialog. zdisplay.exe --help lists everything.

Global hotkeys (defaults)

Hotkey	Action
Ctrl+Alt+↑ / ↓	brightness
Ctrl+Alt+→ / ←	saturation
Ctrl+Alt+K	pause / resume
Ctrl+Alt+P	open the window
Ctrl+Alt+Shift+K	emergency: restore the screen and pause

Configurable in the System tab (Sistema), and each profile can have its own. The fields record the keys: click one and press the combination — Ctrl, Alt, Shift or Win plus a key, or a function key on its own. Backspace or Delete turns a hotkey off. A key the field will not take says why on the spot, a combination already used by another Zdisplay action is refused by name, and one that another program holds is reported under the fields instead of failing silently.

Profiles and automation

A profile stores every adjustment, with optional per-monitor overrides. Six ship built in: Padrão, Jogo, Competitivo, Noite, Filme and Leitura (Default, Game, Competitive, Night, Film, Reading).

Profile selection follows this priority:

1. a profile pinned by hand (tray, window or hotkey);
2. a per-application rule — Zdisplay uses SetWinEventHook to know which program is in the foreground, with no polling loop, so the idle cost is zero;
3. a schedule rule (ranges may cross midnight);
4. the default profile.

A schedule rule's start and end fields accept a clock time (22:00) or the sun itself: sunset, sunrise, and with an offset such as sunset-30 or sunrise+45. Sunset moves by more than two hours over the year, so a fixed range is wrong for half the months. For this to work, fill in Latitude and Longitude in the same tab — without a location, a solar rule simply does not match, rather than switching profiles at the time of a place you are not in.

Within each level, the higher priority wins — for both application and schedule rules — so that two overlapping ranges have an explicit tiebreak instead of depending on line order in the file.

You do not need to know the executable's name. The Process field, in the Automation tab, is a list of the programs you currently have open — the same list as Alt+Tab, re-enumerated every time you open the menu. Pick one and you are done. The field still accepts typed text, for programs that are not running at the moment and for wildcards: cs* matches cs2 and csgo. The use the foreground program button is still there for the fullscreen-game case, which disappears from the list while you are in the Zdisplay window.

Transitions are smoothed frame by frame. Slow hardware commands (DDC/CI and backlight) are sent only at the final value, never during the transition.

Keyboard brightness keys. On a docked laptop, the brightness keys only move the internal panel and the two screens end up mismatched. With brightness keys also apply to external monitors enabled (System tab), Zdisplay notices the change and carries the same value to external monitors over DDC/CI. A profile already managing hardware brightness still wins: in that case mirroring stays out of the way, so the two do not fight.

Configuration

A readable, hand-editable INI file, written atomically:

%APPDATA%\Zdisplay\zdisplay.ini

Portable mode: create an empty file named zdisplay-portable.txt next to the executable and everything is written to that same folder — nothing in the registry (unless you enable autostart), nothing in %APPDATA%.

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Safeguards

The program drives the entire screen. If an adjustment goes wrong, the user may not be able to see well enough to undo it — so the safeguards below exist to make sure that never happens.

Reset restores your screen, not a "neutral" one. At startup Zdisplay reads and stores in baseline.dat each monitor's gamma ramp, its physical brightness and contrast (DDC/CI), its RGB gain and saturation registers, the laptop backlight, and the vibrance already set in the GPU panel. Reset restores exactly those values. If the monitor has an ICC calibration, it is preserved: adjustments are applied on top of the calibration, with interpolation to avoid banding.

Recovery after a crash. While running, a session.lock file exists. If it is still there at the next startup, the previous run did not end cleanly — and Zdisplay restores the screen to the stored state before doing anything else. Not even pulling the plug leaves the screen stuck on an adjustment.

Confirmation with automatic revert. When the adjustments make the screen too dark (less than 20% estimated light), a window appears with a 15-second countdown. Doing nothing undoes the adjustment — the same design Windows uses when changing resolution, and it works precisely in the case where the user cannot see the button. If Zdisplay starts up already in a dark state, the revert point becomes neutral.

Emergency hotkey: Ctrl+Alt+Shift+K. Restores the screen and pauses, from anywhere in Windows. Clearing that field in the settings does not disable it — the default comes back. Also available as zdisplay.exe --panic and in the tray menu.

Absolute light floor. No input path — a hand-edited file, the command line, a profile imported from another machine — can produce less than 8% light. Out-of-range values, NaN and infinity are corrected on read.

The remaining light is measured on the curve that goes to the screen, not estimated by a separate formula: brightness, contrast, gamma, temperature, white balance and shadow detail all enter the calculation, with Rec.709 weights. That matters because each of them genuinely darkens the image — gamma 0.30 with the gains at 50 and temperature at 1500 K leaves the screen nearly black without the brightness slider ever leaving 100%. When the combination falls below the floor, Zdisplay backs off in the order that costs least: first the overlay, then hardware brightness, software brightness, the gains, temperature, gamma and finally contrast.

The configuration is backed up. Atomic writes, a zdisplay.ini.bak of the previous version, and tolerant reading: a corrupted file falls back to the backup, and a file with nothing usable in it is kept as .invalido instead of being silently overwritten.

The monitor's EEPROM is spared. DDC/CI commands go through a queue with a minimum interval of 140 ms, are coalesced when repeated, are never sent during transitions, and have a hard ceiling of 40 per minute per monitor.

Every system change is reversible. The only point that asks for administrator rights is unlocking the gamma range, and the same button undoes it. Autostart uses HKCU\...\Run, which disappears along with the program.

Tests

build.bat test

Or, to build the program and run the suite in one invocation:

make check

474 tests that do not depend on hardware — they run the same on any machine. They cover the color math (5,400 ramp combinations verifying that it never decreases nor blanks the screen), the 441 combinations of the shadow curve, the safety limits, the application and schedule rules, the configuration round trip, ten deliberately corrupted configuration files, the recording of the original state, and eight simulated PC configurations (NVIDIA, AMD, Intel, laptop, virtual machine, four monitors, and a machine with no backend available at all).

A regressions section pins down, one by one, the defects the audit found: the light floor broken through by temperature and gains, the NaN that crossed Clamp, the imported profile that was not sanitized, the discontinuity in the temperature curve at 6600 K, the shadows swallowing the image at low brightness, and the truncated baseline leaving half a state behind.

What the hardware reports about itself is also tested without any hardware: the EDID is assembled byte by byte in the test (header, checksum, manufacturer packed into 5 bits, sRGB and DCI-P3 primaries) and the parser must reject a truncated, zeroed or bad-checksum block — because accepting one would invent a "serial number", and the per-monitor key would then point at the wrong panel. The DDC/CI capability string is tested against a real response, including the case that misleads most: the numbers inside 14(01 05 06) are the values accepted by that code, not codes themselves — and it is precisely that list that decides which inputs the program offers, so it is also tested against firmware that strips all whitespace and against non-hexadecimal garbage, which arrives over I2C and is not trustworthy data.

Converting a WMI instance name to the canonical device path has its own section, because that is what matches the panel WMI commands to the monitor the rest of the program knows: two built-in panels of the same model must stay distinct, or brightness goes to the wrong screen. Per-monitor-model rules are tested round-tripping through the file, and a rule with a typo must be rejected rather than becoming an empty rule that silently does nothing.

Sunrise and sunset are checked against the solstices in São Paulo and London (within 5 to 10 minutes), plus the invariants that catch a sign flip: December is the long day in the southern hemisphere and the short one in the north, at the equator the day lasts a little over 12 h all year, and above the polar circle the function must report that there is no sunrise or sunset rather than returning a number.

The Windows gamma limit

Without a registry change, Windows refuses gamma ramps that deviate too far from linear — and refuses silently. That is why programs of this kind sometimes "do nothing" in strong combinations (low brightness + warm temperature).

Zdisplay does not pretend it worked: when Windows refuses, it searches for the largest fraction of the effect the system accepts, applies that fraction and says so in the status bar and in the diagnostics ("Windows limited the effect to X%"). It also periodically tries to return to the full effect, in case you unlock the range.

This weighs especially on shadow detail: raising the black floor is by definition a large deviation from linear, so it is the adjustment that most often hits the Windows ceiling. It keeps working at the accepted fraction — just not at full strength. If Shadows seems weak, this is almost always why; check the warning in the diagnostics before blaming the slider.

To unlock the full range: System tab → unlock the full gamma range. This writes GdiIcmGammaRange=256 to HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ICM, requires one run as administrator, and only takes effect after restarting the Windows session.

Other honest caveats

• Windows Night light competes for the same ramp. Zdisplay detects it and warns; the "reapply adjustments every N seconds" option (System tab) reasserts the values when another program overwrites them.

• Exclusive-fullscreen games: the gamma ramp and the vendor APIs keep working; the universal matrix and the overlay do not. Use borderless windowed mode if you need universal saturation inside the game.

• HDR enabled makes Windows ignore the gamma ramp — it accepts the write and changes nothing. On those displays brightness goes through the SDR white level, which is the same thing the Windows "SDR content brightness" slider moves: it works per display, with no I2C and no EEPROM writes, and it applies in exclusive-fullscreen games.

  Arrangement	What takes over
  Any display in HDR	brightness: SDR white level, anchored to the value the display already had
  All displays in HDR	contrast and temperature go through the color matrix
  HDR on some displays	contrast and temperature have no effect on the HDR display

  In the mixed arrangement the matrix cannot take over contrast and temperature: its effect covers the entire desktop, and the non-HDR displays — which already received the ramp — would get the adjustment twice. Gamma and shadow detail are curves with no equivalent, so they remain without effect on an HDR display.

  Detection uses the Windows 11 24H2 active mode query, not just the old "advanced color" bit. The difference matters: with Auto Color Management on, the old bit reads true with the display in SDR, and anything trusting it disables gamma and shadows for no reason on a machine where they work.

• DDC/CI writes to the monitor's EEPROM. Zdisplay rate-limits, coalesces requests and never sends commands during transitions — and deliberately does not restore hardware brightness on exit, because that value is yours.

• Monitors that do not follow the standard have their own table. There are panels that report brightness on a different register (and accept the command on 0x10 without changing anything) and firmware that crashes the display driver on receiving DDC/CI. What is already known ships built in; you add the rest in the configuration file, per model:

  [modelo:FUS087C]
  regra=brightness-vcp:6B

  It accepts block, no-caps (do not read the capability string) and brightness-vcp:XX (brightness VCP register), and your rule outranks the built-in one — so you can undo a factory entry that gets in the way of your hardware. The Portuguese spellings written by versions up to 1.1 (bloquear, sem-capacidades, brilho-vcp:XX) are still read. The identifier is the EDID one (three manufacturer letters + product code), visible in the Diagnostics tab.

• "Detected" is not "works". The test the monitor button, in the Diagnostics tab, changes brightness by one step, reads it back, checks it and restores the previous value. That is what separates a monitor that obeys from one that accepts the command, reports success and changes nothing — common enough to deserve proof, and impossible to diagnose by eye.

Questions people actually ask

How do I get a black equalizer without a gaming monitor?

Install Zdisplay and raise the Shadows slider in the Settings tab. It applies the same kind of selective gamma lift that gaming monitors call Black eQualizer, Shadow Boost or Dark Boost, except in software, so it works on any panel — including a laptop screen or an old office monitor whose menu has no such setting. Add Clarity to stop the dark tones flattening into one grey, which is the usual complaint about the hardware versions.

Does digital vibrance work on Intel integrated graphics?

Yes. Intel publishes no driver-level vibrance API, which is why tools built on vendor APIs support NVIDIA and AMD only. Zdisplay falls back to the Windows Magnification color matrix, which is a system feature rather than a driver feature, so saturation works on Intel, on virtual machines, and on any GPU at all. The trade-off is that the matrix is desktop-wide rather than per monitor, and it does not reach exclusive-fullscreen games.

Why does brightness control stop working when I turn HDR on?

Because Windows ignores the gamma ramp on an HDR display: SetDeviceGammaRamp returns success and changes nothing. Zdisplay detects this and switches that display to the SDR white level, the same value the Windows "SDR content brightness" slider moves. It works per display, needs no I2C, and applies inside exclusive-fullscreen games.

Why doesn't my monitor respond to brightness software?

Usually because its DDC/CI capability string is truncated or malformed, and the Windows high-level API validates that string before it will talk to the panel at all. Zdisplay tries the high-level path first, then speaks VCP directly, which recovers many cheap and unbranded monitors. Run zdisplay.exe --diag to see what your specific monitor answered. If it truly does not obey, the Diagnostics tab says so instead of leaving a slider that appears broken.

Does it work in fullscreen games, and does it cost FPS?

The gamma ramp path — brightness, contrast, gamma, temperature and shadow detail — works in exclusive fullscreen and costs nothing per frame, because the GPU applies a 256-entry lookup table on scanout rather than processing the image. The color matrix and the dimming overlay do not reach exclusive fullscreen; use borderless windowed mode if you need those in-game. There is no capture, no injection and no overlay in the rendering path.

Is it safe? What happens if the screen goes black?

An absolute floor of 8% estimated light cannot be crossed by any input, whether from the interface, a hand-edited file, the command line or an imported profile. If a change makes the screen very dark, a countdown appears and reverts it after 15 seconds unless you confirm. Ctrl+Alt+Shift+K restores the display and pauses from anywhere in Windows, and an unclean shutdown is detected and undone at the next start.

Will it flag as a virus or show a SmartScreen warning?

The binary is not code-signed yet, so SmartScreen shows "Windows protected your PC" — click More info, then Run anyway. There is no network code, no telemetry and no elevation in the program; the source is here and the release is built by GitHub Actions, so the published SHA-256 belongs to a build log you can read. Compare the hash before running.

Does it handle multiple monitors, and mixed setups?

Yes. Every adjustment can be set globally or per monitor, and each monitor is identified by its EDID rather than by which port it is plugged into, so its settings survive a cable move. On a hybrid laptop Zdisplay checks which adapter actually drives each display before using a vendor API, instead of sending a command that reports success and changes nothing.

Can I control it from a script, Stream Deck or AutoHotkey?

Yes. With Zdisplay running, any further invocation becomes a command to it: zdisplay.exe --brightness 70, --saturation 130, --profile "Jogo", --shadows 78, --reset, --panic. It answers on the terminal when called from one, and --status and --diag print machine-readable state.

Does it replace Windows Night light?

It covers the same need and more: the Vision tab warms the display on a sunrise/sunset schedule, dims it at night, and layers over your profiles instead of fighting them. Night light writes to the same gamma ramp, so running both means two programs contending for it — Zdisplay detects that and warns you.

Is there a portable version?

The same executable is portable. Put an empty file named zdisplay-portable.txt next to zdisplay.exe and all state is written to that folder — nothing in %APPDATA%, and nothing in the registry unless you enable autostart.

Security

No network, no telemetry, no elevation. The only point that asks for administrator rights is the button that unlocks the gamma range, and it is optional and explicitly confirmed. Autostart uses HKCU\...\Run, trivial to undo.

The system DLLs Zdisplay loads at runtime (nvapi64, atiadlxx, dxva2, magnification) always come from System32, via SetDefaultDllDirectories plus LOAD_LIBRARY_SEARCH_SYSTEM32. Without that, the executable's own directory precedes the system one in the search order — and in a portable program, which is often run from Downloads or a USB stick, a single file with the right name next to it would be enough to become code execution.

The release build fails if the executable or the installer are not marked with DEP, ASLR and high-entropy ASLR. At runtime, both also refuse remote and low-integrity images. The uninstaller removes only the files the installer created; it never recursively deletes a folder chosen by the user.

The single instance and the command channel are per Windows session, not per machine: on a PC with two users logged in, each has their own Zdisplay and neither interferes with the other.

Full policy and reporting channel: SECURITY.md.

Contributing

See CONTRIBUTING.md for building, running the suite, and the rules the codebase does not bend on — the absolute light floor, the exception-free binary, every backend being optional, and the ban on treating "detected" as "works". Participation is governed by the Code of Conduct.

Release history is in the changelog.

Security vulnerabilities do not go in public issues: see SECURITY.md.

Layout

src/
  version.h           version number, used by the .rc and by the code
  ui_dpi.h            per-DPI scaling, shared between the windows
  ui_theme.cpp/.h     dark theme: palette, window frame and owner-drawing
                      for the controls that ignore color messages
  common.*            utilities, log, paths, runtime DLL loading
  core.*              adjustments, profiles, INI, color math, monitors
  backends.h          common interface and capabilities
  backends_display.*  gamma ramp, universal matrix, overlay
  backends_vendor.*   NVAPI (NVIDIA) and ADL (AMD)
  backends_hw.*       DDC/CI and WMI backlight
  engine.*            profile resolution, transitions, watchdog, fallbacks
  services.*          global hotkeys, foreground app, named pipe, autostart
  ui_*.cpp            tray, settings window and events
  icon.cpp            the icon, drawn in code
  main.cpp            entry point, single instance, CLI

The source, the comments and the log are in English. Interface text is written in English too, and the English wording is the key its translations are looked up by, so a call site reads as the sentence it produces.

Other languages

Zdisplay ships in English and Portuguese. It follows the Windows UI language on first run — every regional variant of Portuguese lands on Portuguese, everything else on English — and the choice can be pinned on the System tab or with idioma=pt / idioma=en in zdisplay.ini. The installer follows the same rule.

A language is one column in a table compiled into the binary (src/strings.cpp): there are no translation files to ship, to load or to validate. Adding a language means adding a column; a message with no translation yet falls back to its English wording, so a partial translation shows real text rather than a blank caption.

If you would like to help translate it, open an issue — that contribution is as welcome as any code change.

License

GPL-3.0-or-later. You may use, study, modify and redistribute it. If you distribute a modified version, it must come with its source code and under the same license.