Converting Transparency Level 0-255 To Percentage

[WildByDesign]

Either I had too much coffee today or possibly not enough, but the math part of my brain is not working right now. 😆

With _WinAPI_SetLayeredWindowAttributes there is a Transparency level of 0 to 255. I would like to simplify what the user needs to enter in an INI file with a value of 0 to 100, representing percentage.

So if a user enters 100, that would need to convert to 255 in a math function. 0 would obviously be 0. But it is the whole math thing that is escaping me right now.

Could someone please point me in the right direction for this? Thank you

[argumentum]

255/100 = 2.55 ?
then 100 * 2.55 = 255 ?

Multiply the 0 to 100 by 2.55  

[WildByDesign]

Your math is always sharp. Thank you so much.

[argumentum]

ConsoleWrite( myPercentThing(200) & @CRLF)
ConsoleWrite( myPercentThing(100) & @CRLF)
ConsoleWrite( myPercentThing(50) & @CRLF)
ConsoleWrite( myPercentThing(0) & @CRLF)
ConsoleWrite( myPercentThing(-1000) & @CRLF)
Func myPercentThing($vDecimal)
    $vDecimal = ($vDecimal < 0 ? 0 : $vDecimal)
    $vDecimal = ($vDecimal > 100 ? 100 : $vDecimal)
    Return Ceiling($vDecimal * 2.55) ; round up
EndFunc

0 visibility is totally transparent. Make a minimum of 50 🤔 

[WildByDesign]

That is really neat. Thank you for sharing. I can tell from this (and many of your previous functions) that you truly enjoy doing great things with math.

[Somerset]

The starting digit is 0 not 1, so it is 256 levels of transparency.

[WildByDesign]

9 minutes ago, Somerset said:

The starting digit is 0 not 1, so it is 256 levels of transparency.

You are absolutely right. So that would make the multiplier 2.56 then. Thanks for the heads up on that one.

[argumentum]

1 hour ago, WildByDesign said:

So that would make the multiplier 2.56 then

Would be ( 2.55 * n ) + 1
But "Transparency: A number in the range 0 - 255. The lower the number, the more transparent the window will become. 255 = Solid, 0 = Invisible." 0x00 to 0xFF

Always doublecheck everything. Anyone can misremember or be just plain wrong. Me, you, @TheSaint ... anyone 

1 hour ago, Somerset said:

The starting digit is 0 not 1, so it is 256 levels of transparency.

And @Somerset can say something that is true

Edited 22 hours ago by argumentum

[Somerset]

I've done enough editing of image files to know a few things.

If you are going to have % of transparency you should have a small input section from 0 - 255 as exacting levels of transparency. Most people cannot tell the difference of 1% to about 5% level of transparency, but some might want the option to have exacting levels for better control.

42 minutes ago, argumentum said:

And @Somerset can say something that is true

Don't presume that about me. I don't like to lie as much as stretching the truth so far that is snaps back on me like a rubber band that has broke from the stress.

 

[argumentum]

20 minutes ago, Somerset said:

Most people cannot tell the difference of 1% to about 5% level of transparency, but some might want the option to have exacting levels for better control.

True.
I rather enter a value between 0 and 255 than 0 to 100 because, why dumbify something when there is no need.
 

Spoiler

#include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>
Example()
Func Example()
    GUICreate("slider", 220, 100, 100, 200)
    GUISetBkColor(0x00E0FFFF)     ; will change background color
    Local $idSlider1 = GUICtrlCreateSlider(10, 10, 200, 20)
    GUICtrlSetLimit(-1, 255, 0)     ; change min/max value
    Local $idButton = GUICtrlCreateButton("Value?", 75, 70, 70, 20)
    GUISetState(@SW_SHOW)
    GUICtrlSetData($idSlider1, 45)     ; set cursor
    Local $idMsg
    ; Loop until the user exits.
    Do
        $idMsg = GUIGetMsg()
        If $idMsg = $idButton Then
            MsgBox($MB_SYSTEMMODAL, "slider1", GUICtrlRead($idSlider1), 2)
        EndIf
    Until $idMsg = $GUI_EVENT_CLOSE
EndFunc   ;==>Example

 

[TheSaint]

6 hours ago, Somerset said:

Don't presume that about me.

Because that can make a Pres out of U and Me ... whatever a Pres is ... maybe some kind of Trump thing.  

6 hours ago, Somerset said:

I don't like to lie as much as stretching the truth so far that is snaps back on me like a rubber band that has broke from the stress.

Not only that, but the truth can be stretched so much it becomes unrecognizable ... that's when Oranges can be like Apples and Bananas like Sausages ... so Gastronomy suffers and we all end up with a belly ache. I don't know about you, but I prefer to not have sausages in my Fruit Salad ... or Bananas and Mash.

[UEZ]

A generic map function:

;Coded by UEZ build 2025-10-29
Func Map($val, $source_start, $source_stop, $dest_start, $dest_stop)
    Return (($val - $source_start) * ($dest_stop - $dest_start) / ($source_stop - $source_start) + $dest_start)
EndFunc

$iCol = Int(Map(87, 0, 100, 0, 255))
ConsoleWrite($iCol & " - 0x" & Hex($iCol, 2) & @CRLF) ;87% from color value (0 - 255)

$iCol = 1 + Int(Map($iCol, 0, 255, 0, 100)) ;and back again
ConsoleWrite($iCol & " - 0x" & Hex($iCol, 2) & @CRLF)

 

Edited 14 hours ago by UEZ

[WildByDesign]

1 hour ago, UEZ said:

A generic map function:

This is really nice. Accurate as well and with no decimal places. Thank you for sharing.