QB64-PE/internal/help/_ALPHA32.txt

The [[_ALPHA32]] function returns the alpha transparency level of a 32 bit color value only.


{{PageSyntax}}
:{{Parameter|alpha&}} = '''_ALPHA32({{Parameter|colour32~&}})'''


{{Parameters}}
* {{Parameter|colour32&}} is the [[_UNSIGNED]] [[LONG]] 32 bit color value used to retrieve the alpha level.
** Color values that are set as a [[_CLEARCOLOR]] always have an alpha level of 0 (transparent).
** [[_SETALPHA]] can set any alpha level from 0 or fully transparent to 255 or opaque.
** Normal color values that are set by [[_RGB]] or [[_RGB32]] always have an alpha level of 255(opaque).


''Usage:''
* In 4(16 color) or 8(256 color) bit palette screens the function will return 0.
* [[_RED32]], [[_GREEN32]], [[_BLUE32]] and [[_ALPHA32]] are all equivalent to [[_RED]], [[_GREEN]], [[_BLUE]] and [[_ALPHA]] but they are highly optimized and only accept a 32-bit color (RGBA) value. Using these in your code (opposed to dividing then ANDing 32-bit color values) makes code easy to read.
* '''NOTE: 32 bit [[_NEWIMAGE]] screen page backgrounds are transparent black or [[_ALPHA]] 0. Use [[_DONTBLEND]] or [[CLS]] for opaque!'''


''Example:'' Finding the alpha transparency level in a 32 bit screen using an [[_RGBA]]  [[_UNSIGNED]] [[LONG]] color value.
{{CodeStart}} '' ''
{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)

clr~& = {{Cl|_RGBA}}(255, 0, 255, 192)
{{Cl|PRINT}} "Color:"; clr~&

{{Cl|COLOR}} clr~&
{{Cl|PRINT}} "Alpha32:"; {{Cl|_ALPHA32}}(clr~&)

{{Cl|END}} '' ''
{{CodeEnd}}
{{OutputStart}}{{text|Color: 3237937407|#FFFFFF}}
{{text|Alpha32: 192|#FF00FF}}
{{OutputEnd}}
: ''Notes:'' The color value is equivalent to [[&H|hexadecimal]] &HC0FF00FF where &HC0 equals 192. [[_RGB]] alphas are always &HFF(255).


{{PageSeeAlso}}
* [[_ALPHA]], [[_SETALPHA]]
* [[_RGBA]], [[_RGBA32]] {{text|(set color with alpha)}}
* [[_RED]], [[_GREEN]], [[_BLUE]]
* [[_RED32]], [[_GREEN32]]. [[_BLUE32]]
* [[_CLEARCOLOR]], [[_CLEARCOLOR (function)]]
* [[Images]]


{{PageNavigation}}