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53 lines
2 KiB
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53 lines
2 KiB
Plaintext
{{QBDLDATE:05-20-2022}}
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{{QBDLTIME:23:06:23}}
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{{DISPLAYTITLE:_ALPHA32}}
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The [[_ALPHA32]] function returns the alpha transparency level of a 32 bit color value.
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{{PageSyntax}}
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:{{Parameter|alpha&}} = [[_ALPHA32]]({{Parameter|color32~&}})'''
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{{Parameters}}
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* {{Parameter|color32&}} is the [[_UNSIGNED]] [[LONG]] 32 bit color value used to retrieve the alpha level.
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** Color values that are set as a [[_CLEARCOLOR]] always have an alpha level of 0 (transparent).
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** [[_SETALPHA]] can set any alpha level from 0 (or fully transparent) to 255 (or opaque).
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** Normal color values that are set by [[_RGB]] or [[_RGB32]] always have an alpha level of 255 (opaque).
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{{PageDescription}}
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* In 4-bit (16 colors) or 8-bit (256 colors) palette screens the function will return 0.
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* [[_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.
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* '''NOTE: 32 bit [[_NEWIMAGE]] screen page backgrounds are transparent black or [[_ALPHA]] 0. Use [[_DONTBLEND]] or [[CLS]] for opaque!'''
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{{PageExamples}}
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''Example:'' Finding the alpha transparency level in a 32 bit screen using an [[_RGBA]] [[_UNSIGNED]] [[LONG]] color value.
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{{CodeStart}}
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{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)
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clr~& = {{Cl|_RGBA}}(255, 0, 255, 192)
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{{Cl|PRINT}} "Color:"; clr~&
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{{Cl|COLOR}} clr~&
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{{Cl|PRINT}} "Alpha32:"; {{Cl|_ALPHA32}}(clr~&)
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{{Cl|END}}
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{{CodeEnd}}
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{{OutputStart}}{{text|Color: 3237937407|#FFFFFF}}
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{{text|Alpha32: 192|#FF00FF}}
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{{OutputEnd}}
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: ''Notes:'' The color value is equivalent to [[&H|hexadecimal]] &HC0FF00FF where &HC0 equals 192. [[_RGB]] alphas are always &HFF(255).
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{{PageSeeAlso}}
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* [[_ALPHA]], [[_SETALPHA]]
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* [[_RGBA]], [[_RGBA32]] {{text|(set color with alpha)}}
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* [[_RED]], [[_GREEN]], [[_BLUE]]
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* [[_RED32]], [[_GREEN32]]. [[_BLUE32]]
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* [[_CLEARCOLOR]], [[_CLEARCOLOR (function)]]
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* [[Images]]
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{{PageNavigation}}
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