18 replies to this topic

[wakillon]

It's late and Screen brightness hurts your eyes
and you do not remember how you can regulate it ?

I get a solution !

TinyBrightnessControler

Left click on Tray Icon for show Controler and Right click for Tray Menu, that's all !

AutoIt        expandcollapse  popup

#Region ;**** Directives created by AutoIt3Wrapper_GUI ****
#AutoIt3Wrapper_icon=Electric bulb1.ico
#AutoIt3Wrapper_outfile=TinyBrightnessControler.exe
#AutoIt3Wrapper_Res_Description=Adjust Screen Brightness
#AutoIt3Wrapper_Res_Fileversion=1.0.0.2
#AutoIt3Wrapper_Res_Fileversion_AutoIncrement=p
#AutoIt3Wrapper_Res_LegalCopyright=Copyright 2011 wakillon
#AutoIt3Wrapper_Res_SaveSource=y
://////=__=
://////=__=
#EndRegion ;**** Directives created by AutoIt3Wrapper_GUI ****

#cs -----------------------------------------------------------------------------------------------------------

AutoIt Version : 3.3.6.1
Author       : wakillon
                 Based on the noctis Post : <a href='http://autoit.de/index.php?page=Thread&postID=83474#post83474' class='bbc_url' title='External link' rel='nofollow external'>http://autoit.de/index.php?page=Thread&postID=83474#post83474</a>
Title : TinyBrightnessControler
Script Fonction : Adjust Screen Brightness.
                 Left click on Tray Icon for show Controler and Right click for Tray Menu.

#ce -----------------------------------------------------------------------------------------------------------

#include <WindowsConstants.au3>
#include <GuiSlider.au3>

Opt ( "TrayOnEventMode", 1 )
Opt ( "TrayMenuMode", 1 )
OnAutoItExitRegister ( "_Exit" )

Global Const $TRAY_UNCHECKED = 4
Global Const $TRAY_EVENT_PRIMARYDOWN = -7
Global $_Rgb, $_DefaultItem, $_GetPosOld, $_AboutItem, $_TitleItem, $_UpdateItem, $_SaveItem
Global $_Gui, $_Slider, $_Label1, $_Label2, $_Dll
Global $_Version = _GetScriptVersion ( )

_TrayMenu ( )
$_Rgb = RegRead ( "HKEY_LOCAL_MACHINESoftwareTBC", "Gamma" )
If $_Rgb = '' Then $_Rgb =128
$_GetPosOld=$_Rgb
_SetGamma ( $_Rgb, $_Rgb, $_Rgb )

While 1
    Sleep ( 10 )
WEnd

Func _DisplaySlider ( )
    Local $_MousePos = MouseGetPos ( )
    Local $_GuiWight= 50, $_GuiHeight=230
    Local $_Gui = GUICreate ( "", $_GuiWight, $_GuiHeight, $_MousePos[0]-$_GuiWight/2, @DesktopHeight - $_GuiHeight - _GetTaskbarHeight ( ) -2, _
    BitOR ( $WS_POPUP, $WS_BORDER ), $WS_EX_TOPMOST, WinGetHandle ( AutoItWinGetTitle ( ) ) )
    $_Label1 = GUICtrlCreateLabel ( "Min", 15, 10 )
    $_Slider = GUICtrlCreateSlider ( 15, 30, 20, 180, BitOR ( $TBS_VERT, $TBS_TOOLTIPS, $TBS_AUTOTICKS ) )
    GUICtrlSetLimit ( -1, 256, 0 )
    $_Label2 = GUICtrlCreateLabel ( "Max", 15, 210 )
    GUISetState ( )
    _GUICtrlSlider_SetPos ( $_Slider, $_GetPosOld )
    $_TimerInit = TimerInit ( )
    While 1
        $_GetPos = _GUICtrlSlider_GetPos ( $_Slider )
        If $_GetPos <> $_GetPosOld Then
            $_Rgb = $_GetPos
         _SetGamma ( $_Rgb, $_Rgb, $_Rgb )
         $_GetPosOld = $_GetPos
         $_TimerInit = TimerInit ( )
     EndIf
     If _IsMouseOverCtrls ( $_Gui ) Then $_TimerInit = TimerInit ( )
     $_TimerDiff = Round ( TimerDiff ( $_TimerInit )/ 1000 )
     If $_TimerDiff > 2 Then ExitLoop
    WEnd
    GUIDelete ( )
EndFunc ;==> _DisplaySlider ( )

Func _IsMouseOverCtrls ( $_GuiHwnd, $_Active=0 )
    $_CursorInfo = GUIGetCursorInfo ( $_GuiHwnd )
    If Not @error Then
        Switch $_CursorInfo[4]
            Case $_Slider, $_Label1, $_Label2
                Return 1
        EndSwitch
    EndIf
EndFunc ;==> _IsMouseOverCtrls ( )

Func _Normal ( )
    TrayItemSetState ( $_DefaultItem, $TRAY_UNCHECKED )
    $_Rgb = 128
    $_GetPosOld = 128
    _SetGamma ( $_Rgb, $_Rgb, $_Rgb )
EndFunc ;==> _Normal ( )

Func _Exit ( )
    DllClose ( $_Dll )
    Exit
EndFunc ;==> _Exit ( )

Func _SetGamma ( $vRed=128, $vGreen=128, $vBlue=128 )
    Local $n_ramp, $rVar, $gVar, $bVar, $Ret, $i, $dc
    If $vRed < 0 Or $vRed > 386 Then Return -1
    If $vGreen < 0 Or $vGreen > 386 Then Return -1
    If $vBlue < 0 Or $vBlue > 386 Then Return -1
    $dc = DLLCall ( "user32.dll", "int", "GetDC","hwnd", 0 )
    $n_ramp = DllStructCreate ( "short[" & ( 256*3 ) & "]" )
    For $i = 0 to 256
    $rVar = $i * ( $vRed + 128 )
    If $rVar > 65535 Then $rVar = 65535
    $gVar = $i * ( $vGreen + 128 )
    If $gVar > 65535 Then $gVar = 65535
    $bVar = $i * ( $vBlue + 128 )
    If $bVar > 65535 Then $bVar = 65535
    DllStructSetData ( $n_ramp, 1, Int ( $rVar ), $i )  ; red
    DllStructSetData ( $n_ramp, 1, Int ( $gVar ), $i+256 ) ; green
    DllStructSetData ( $n_ramp, 1, Int ( $bVar ), $i+512 ) ; blue
    Next
    $ret = DLLCall ( "gdi32.dll", "int", "SetDeviceGammaRamp", "int", $dc[0], "ptr", DllStructGetPtr ( $n_Ramp ) )
    $dc = 0
    $n_Ramp = 0
EndFunc ;==> _SetGamma ( )

Func _TrayMenu ( )
    $_TempDir = @TempDir & 'TBCskin'
    If Not FileExists ( $_TempDir ) Then DirCreate ( $_TempDir )
    If Not FileExists ( $_TempDir & 'Electric bulb1.ico' ) Then _
    InetGet ( 'http://tinyurl.com/d3srkot', $_TempDir & 'Electric bulb1.ico', 9, 0 )
    TraySetToolTip ( $_Version & @CRLF & @CRLF & '* Left click for show Controler' & @CRLF & '* Right click for Tray Menu' & @CRLF )
    TraySetIcon ( $_TempDir & 'Electric bulb1.ico' )
    TraySetClick ( 16 )
    TraySetOnEvent ( $TRAY_EVENT_PRIMARYDOWN, '_DisplaySlider' )
    $_TitleItem = TrayCreateItem ( $_Version )
    TrayItemSetOnEvent ( -1, '_UnCheck' )
    TrayCreateItem ( '' )
    $_DefaultItem = TrayCreateItem ( 'Set Brightness To Normal' )
    TrayItemSetOnEvent ( -1, '_Normal' )
    TrayCreateItem ( '' )
    $_UpdateItem = TrayCreateItem ( "See For Update" )
    TrayItemSetOnEvent ( -1, '_SeeForUpdate' )
    TrayCreateItem ( "" )
    $_AboutItem = TrayCreateItem ( "About" )
    TrayItemSetOnEvent ( -1, '_About' )
    TrayCreateItem ( "" )
    $_SaveItem = TrayCreateItem ( "Save Settings" )
    TrayItemSetOnEvent ( -1, '_Save' )
    TrayCreateItem ( "" )
    $_ExitItem = TrayCreateItem ( 'Exit' )
    TrayItemSetOnEvent ( -1, '_Exit' )
    TraySetState ( 4 )
EndFunc ;==> _TrayMenu ( )

Func _Save ( )
    TrayItemSetState ( $_SaveItem , $TRAY_UNCHECKED )
    RegWrite ( "HKEY_LOCAL_MACHINESoftwareTBC", "Gamma", "REG_SZ", $_Rgb )
    Msgbox ( 262144+4160, "Saved", "Gamma Settings have been saved", 3 )
EndFunc

Func _SeeForUpdate ( )
    TrayItemSetState ( $_UpdateItem , $TRAY_UNCHECKED )
    ShellExecute ( 'http://www.autoitscript.com/forum/topic/127668-tinybrightnesscontroler/' )
EndFunc ;==> _SeeForUpdate ( )

Func _UnCheck ( )
    TrayItemSetState ( $_TitleItem , $TRAY_UNCHECKED )
EndFunc ;==> _UnCheck ( )

Func _GetScriptVersion ( )
    If Not @Compiled Then
        Return StringTrimRight ( @ScriptName, 4 ) & ' © wakillon 2010 - 2011'
    Else
        Return StringTrimRight ( @ScriptName, 4 ) & ' v' & FileGetVersion ( @ScriptFullPath ) & ' © wakillon 2010 - 2011'
    EndIf
EndFunc ;==> _GetScriptVersion ( )

Func _About ( )
    TrayItemSetState ( $_AboutItem , $TRAY_UNCHECKED )
    Msgbox ( 262144+4160, "About : ", $_Version & @CRLF & @CRLF & "April 2011" & @CRLF & @CRLF & "Based on the noctis's Gamma Topic on AutoIt.de" & @CRLF & @CRLF & "wakillon." & @CRLF & " " )
EndFunc ;==> _About ( )

Func _GetTaskbarHeight ( )
    $_OptOld = Opt ( "WinTitleMatchMode", 4 )
    $_WinPos = WinGetPos ( "classname=Shell_TrayWnd" )
    If @error Then Return -1
    Opt ( "WinTitleMatchMode", $_OptOld )
    Return $_WinPos[3]
EndFunc ;==> _GetTaskbarHeight ( )

Scripts and executables with full embeded files are available on GoogleCode, see link in my sig.

Comments are welcome !

All this time spent in front of the screen, remember to protect your eyes !

Edited by wakillon, 08 October 2012 - 04:42 PM.

[Foxhound]

Nice one Wakil, but question:

Is there any way you could use the DeviceIoControl to set backlight brightness instead of Gamma? I've gotten started on it but I'm having trouble with creating the handle from CreateFile (first parameter).

#include "winapi.au3"  
;CreateFile 
;$cHandle = DllCall("User32.dll","HANDLE","CreateFile","str", ;IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS
 $DISPLAY_BRIGHTNESS = DllStructCreate("uchar 0x00000003;uchar 50;uchar 10") 

DllCall("User32.dll","int","DeviceIoControl","HANDLE",$cHandle,"dword","IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS","ptr",DllStructGetPtr($DISPLAY_BRIGHTNESS),"int",500,"int","none","int",0,"int","none","ptr","none") 
 ConsoleWrite(_WinAPI_GetLastError()&@CRLF)

I'm not so good with DllCall yet

Anyway nice script

[JScript]

I like it! Very good indeed!
Thanks for sharing...

[reb]

This is really a good script and works well on my win7 64 laptop.

Thanks a lot for sharing with us.

REB

[wakillon]

Nice one Wakil, but question:

Is there any way you could use the DeviceIoControl to set backlight brightness instead of Gamma? I've gotten started on it but I'm having trouble with creating the handle from CreateFile (first parameter).

#include "winapi.au3"  
;CreateFile 
;$cHandle = DllCall("User32.dll","HANDLE","CreateFile","str", ;IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS
 $DISPLAY_BRIGHTNESS = DllStructCreate("uchar 0x00000003;uchar 50;uchar 10") 

DllCall("User32.dll","int","DeviceIoControl","HANDLE",$cHandle,"dword","IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS","ptr",DllStructGetPtr($DISPLAY_BRIGHTNESS),"int",500,"int","none","int",0,"int","none","ptr","none") 
 ConsoleWrite(_WinAPI_GetLastError()&@CRLF)

I'm not so good with DllCall yet

Anyway nice script

Thanks !


I have googling a long time for find an "universal" solution for set screen brightness.
I have found autoit examples with device control, or by others way, but a probem was back often : compatibility with OS or driver.
So i reduce my ambitions to gamma settings who is not a really "brightness" settings,
but who can be used by all !

An example with device control found but not working for me :

Say me if you managed to make it work !

Edited by wakillon, 17 April 2011 - 09:59 AM.

[wakillon]

Sorry but i can't edit my AutoIt tags part it return error each time !

@Foxhound

here is the script :

AutoIt        expandcollapse  popup

#include <WinAPI.au3>

$tagDISPLAY_BRIGHTNESS = "ubyte ucDisplayPolicy;ubyte ucACBrightness;ubyte ucDCBrightness"
Global Const $IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS = Int(0x00230498)
Global Const $IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS = Int(0x0023049C)
Global Const $IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS = Int(0x00230494)
Global Const $hLCD = _WinAPI_CreateFile("\\.\LCD", 3, 2, 7)

ConsoleWrite ( "_GetDisplayBrightness() : " & _GetDisplayBrightness() & @Crlf )
ConsoleWrite ( "_GetSupportedBrightness() : " & _GetSupportedBrightness() & @Crlf )

Func _GetDisplayBrightness()
    $DISPLAY_BRIGHTNESS = DllStructCreate($tagDISPLAY_BRIGHTNESS)
    DllStructSetData($DISPLAY_BRIGHTNESS, "ucDisplayPolicy", 0x1)
    DllStructSetData($DISPLAY_BRIGHTNESS, "ucACBrightness", 0x20)
    DllStructSetData($DISPLAY_BRIGHTNESS, "ucDCBrightness", 0x20)
    $ret = DllCall( _
    "kernel32.dll", "int", _
    "DeviceIoControl", _
    "hwnd", $hLCD, _
    "int", $IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS, _
    "ptr", 0, _
    "int", 0, _
    "ptr", DllStructGetPtr($DISPLAY_BRIGHTNESS), _
    "int", DllStructGetSize($DISPLAY_BRIGHTNESS), _
    "int*", 0, _
    "ptr", 0 )
    Return SetError(@error, DllStructGetData($DISPLAY_BRIGHTNESS, "ucDCBrightness"), DllStructGetData($DISPLAY_BRIGHTNESS, "ucACBrightness"))
EndFunc ;==> _GetDisplayBrightness ( )

Func _GetSupportedBrightness()
    $SURPPORTED_BRIGHTNESS = DllStructCreate("ubyte suported[256]")
    $ret = DllCall( _
    "kernel32.dll", "int", _
    "DeviceIoControl", _
    "hwnd", $hLCD, _
    "int", $IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS, _
    "ptr", 0, _
    "int", 0, _
    "ptr", DllStructGetPtr($SURPPORTED_BRIGHTNESS), _
    "int", DllStructGetSize($SURPPORTED_BRIGHTNESS), _
    "int*", 0, _
    "ptr", 0 )
    If $ret[0] = 0 Or $ret[7] = 0 Then Return SetError(@error, 0, 0)
    Dim $brightness[$ret[7]]
    For $i = 0 To UBound($brightness) - 1
        $brightness[$i] = DllStructGetData($SURPPORTED_BRIGHTNESS, "suported", $i + 1)
    Next
    Return SetError(0, $ret[7], $brightness)
EndFunc ;==> _GetSupportedBrightness ( )

Func _SetDisplayBrightness($ac = -1, $dc = -1)
    $DISPLAY_BRIGHTNESS = DllStructCreate($tagDISPLAY_BRIGHTNESS)
    Local $policy = 0
    If $ac > -1 Then
        $policy += 1
        DllStructSetData($DISPLAY_BRIGHTNESS, "ucACBrightness", $ac)
    EndIf
    If $dc > -1 Then
        $policy += 2
        DllStructSetData($DISPLAY_BRIGHTNESS, "ucDCBrightness", $dc)
    EndIf
    DllStructSetData($DISPLAY_BRIGHTNESS, "ucDisplayPolicy", $policy)
    $ret = DllCall( _
    "kernel32.dll", "int", _
    "DeviceIoControl", _
    "hwnd", $hLCD, _
    "int", $IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, _
    "ptr", DllStructGetPtr($DISPLAY_BRIGHTNESS), _
    "int", DllStructGetSize($DISPLAY_BRIGHTNESS), _
    "ptr", 0, _
    "int", 0, _
    "int*", 0, _
    "ptr", 0 )
    Return SetError(@error, 0, $ret[0])
EndFunc ;==> _SetDisplayBrightness ( )

Edited by wakillon, 17 April 2011 - 10:07 AM.

[wakillon]

I like it! Very good indeed!
Thanks for sharing...

This is really a good script and works well on my win7 64 laptop.

Thanks a lot for sharing with us.

REB

I'm glad you like it !
Thanks to both.

[Yashied]

Look nice but there is one suggestion. It would be nice if you kept the proportions of RGB values ​​in the LUT. For examples:

Here is the LUT before using TBC.



After using TBC.

[Foxhound]

It worked! But it only to decrease brightness, not increase it.

Supported brightness for my laptop says 95, I put 92 for _SetDisplayBrightness() but it decreases the brightness all the way down for some reason

Edited by Foxhound, 17 April 2011 - 02:06 PM.

[wakillon]

Look nice but there is one suggestion. It would be nice if you kept the proportions of RGB values ​​in the LUT. For examples:

Thanks !
Idea is interesting but i don't find any working function for get gamma settings and proportions !
If you have any suggestion...

Edit : I'm searching for GetDeviceGammaRamp but unsuccessfully.

Edited by wakillon, 17 April 2011 - 03:12 PM.

[wakillon]

It worked! But it only to decrease brightness, not increase it.

Supported brightness for my laptop says 95, I put 92 for _SetDisplayBrightness() but it decreases the brightness all the way down for some reason

You're lucky !
On what OS are you ?
I'm on xpsp3 and functions return 0 !

[Foxhound]

You're lucky !
On what OS are you ?
I'm on xpsp3 and functions return 0 !

Windows 7 Professional x86

[wakillon]

Windows 7 Professional x86

So, i was right when i talk about compatibility with OS !
Let me know If you find a multi OS solution !

[Yashied]

Windows 7 Professional x86

Works fine for me under this OS! Note, not all adapters support downloadable gamma ramps in hardware.

I'm searching for GetDeviceGammaRamp but unsuccessfully.

AutoIt        expandcollapse  popup

#Include <Array.au3>
#Include <WinAPIEx.au3>

Dim $Delta[256][3]

$hForm = GUICreate('Lookup Table', 256, 256)
$Pic = GUICtrlCreatePic('', 0, 0, 255, 255)

$hDC = _WinAPI_GetDC(0)
$tRamp = DllStructCreate('ushort[768]')
$Ret = DllCall('gdi32.dll', 'int', 'GetDeviceGammaRamp', 'hwnd', $hDC, 'ptr', DllStructGetPtr($tRamp))
$hMemDC = _WinAPI_CreateCompatibleDC($hDC)
$hBitmap = _WinAPI_CreateCompatibleBitmapEx($hDC, 256, 256, 0)
$hSv1 = _WinAPI_SelectObject($hMemDC, $hBitmap)
$hPen = _WinAPI_GetStockObject($DC_PEN)
$hSv2 = _WinAPI_SelectObject($hMemDC, $hPen)
_WinAPI_SetROP2($hMemDC, $R2_XORPEN)
_WinAPI_ReleaseDC(0, $hDC)
$Rgb = 0xFF0000
$Count = 1
For $i = 0 To 2
    _WinAPI_SetDCPenColor($hMemDC, BitShift($Rgb, 8 * $i))
    For $j = 0 To 255
        $Delta[$j][$i] = Round(DllStructGetData($tRamp, 1, $Count) - $j / 255 * 65280) ; 65280 ???
        If $j Then
            _WinAPI_LineTo($hMemDC, $j + 1, Round(255 * (1 - DllStructGetData($tRamp, 1, $Count) / 65280)) - 1)
        Else
            _WinAPI_MoveTo($hMemDC, 0, Round(255 * (1 - DllStructGetData($tRamp, 1, $Count) / 65280)))
        EndIf
        $Count += 1
    Next
Next
_WinAPI_SelectObject($hMemDC, $hSv1)
_WinAPI_SelectObject($hMemDC, $hSv2)
_WinAPI_DeleteObject($hPen)
_WinAPI_DeleteDC($hMemDC)

GUICtrlSendMsg($Pic, 0x0172, 0, $hBitmap)
GUISetState()

_ArrayDisplay($Delta)

Do
Until GUIGetMsg() = -3

Edited by Yashied, 17 April 2011 - 05:02 PM.

[wakillon]

@Yashield
I have found this one, but doesn't give same results as yours...

AutoIt        expandcollapse  popup

#include <Array.au3>

$_GetGammaRamp = _GetGammaRamp()
_ArrayDisplay ( $_GetGammaRamp )

Func _GetGammaRamp()
    Local $dc, $m_RampSaved,$ret,$avDisplay
    $dc = DLLCall("user32.dll","int","GetDC","hwnd",0)
    $m_RampSaved = DllStructCreate("short[" & (256*3) & "]")
    $ret = DLLCall("gdi32.dll","int","GetDeviceGammaRamp", "int",$dc[0],"ptr",DllStructGetPtr($m_RampSaved))
    If Not $ret[0] Then MsgBox(4096,"WARNING", "WARNING: Cannot initialize DeviceGammaRamp.")
    $avDisplay = _GammaTo2d($m_RampSaved)
    $dc = 0
    $m_RampSaved = 0
    Return $avDisplay
EndFunc ;==> _GetGammaRamp()

Func _GammaTo2d($vm_RampSaved)
    Local $avDisplay[257][3]
    For $i = 0 to 256
        $avDisplay[$i][0] = DllStructGetData($vm_RampSaved,1,$i)
        $avDisplay[$i][1] = DllStructGetData($vm_RampSaved,1,$i + 256)
        $avDisplay[$i][2] = DllStructGetData($vm_RampSaved,1,$i + 512)
    Next
    Return $avDisplay
EndFunc ;==> _GammaTo2d()

[Yashied]

Not all direct color video boards support loadable gamma ramps.

What gives the following code?

#Include <WinAPI.au3>

$hDC = _WinAPI_GetDC(0)
$tRamp = DllStructCreate('ushort[768]')
$Ret = DllCall('gdi32.dll', 'int', 'GetDeviceGammaRamp', 'hwnd', $hDC, 'ptr', DllStructGetPtr($tRamp))
If (@error) Or (Not $Ret[0]) Then
    MsgBox(16, @error, _WinAPI_GetLastErrorMessage())
Else
    MsgBox(0, '', 'OK')
EndIf
_WinAPI_ReleaseDC(0, $hDC)

Edit:

Func _GammaTo2d($vm_RampSaved)
    Local $avDisplay[256][3]
    For $i = 0 To 255
        $avDisplay[$i][0] = DllStructGetData($vm_RampSaved, 1, $i + 1)
        $avDisplay[$i][1] = DllStructGetData($vm_RampSaved, 1, $i + 1 + 256)
        $avDisplay[$i][2] = DllStructGetData($vm_RampSaved, 1, $i + 1 + 512)
    Next
    Return $avDisplay
EndFunc   ;==>_GammaTo2d

Edited by Yashied, 17 April 2011 - 05:19 PM.

[wakillon]

What gives the following code?

It gives Ok

Edit : And your function ( #post 14 ) give an array with only 256 in all the array.

Edited by wakillon, 17 April 2011 - 05:27 PM.

[Yashied]

It gives Ok

Then structure was filled successfully.

[Yashied]

Maximum value for each color is 65280 instead of 65535. Why? Maximum number of 8-bit number is 0xFF (255). Maximum number of gradations for each channel is 256.

255 * 256 = 65280