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55 lines
2 KiB
Markdown
55 lines
2 KiB
Markdown
The [_ALPHA32](_ALPHA32) function returns the alpha transparency level of a 32 bit color value.
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## Syntax
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> alpha& = [_ALPHA32](_ALPHA32)(color32~&)**
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## Parameter(s)
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* color32& is the [_UNSIGNED](_UNSIGNED) [LONG](LONG) 32 bit color value used to retrieve the alpha level.
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* Color values that are set as a [_CLEARCOLOR](_CLEARCOLOR) always have an alpha level of 0 (transparent).
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* [_SETALPHA](_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](_RGB) or [_RGB32](_RGB32) always have an alpha level of 255 (opaque).
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## Description
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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](_RED32), [_GREEN32](_GREEN32), [_BLUE32](_BLUE32) and [_ALPHA32](_ALPHA32) are all equivalent to [_RED](_RED), [_GREEN](_GREEN), [_BLUE](_BLUE) and [_ALPHA](_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](_NEWIMAGE) screen page backgrounds are transparent black or [_ALPHA](_ALPHA) 0. Use [_DONTBLEND](_DONTBLEND) or [CLS](CLS) for opaque!**
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## Example(s)
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Finding the alpha transparency level in a 32 bit screen using an [_RGBA](_RGBA) [_UNSIGNED](_UNSIGNED) [LONG](LONG) color value.
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```vb
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SCREEN _NEWIMAGE(640, 480, 32)
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clr~& = _RGBA(255, 0, 255, 192)
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PRINT "Color:"; clr~&
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COLOR clr~&
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PRINT "Alpha32:"; _ALPHA32(clr~&)
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END
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```
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```text
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Color: 3237937407
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Alpha32: 192
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```
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> *Notes:* The color value is equivalent to [&H](&H) &HC0FF00FF where &HC0 equals 192. [_RGB](_RGB) alphas are always &HFF(255).
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## See Also
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* [_ALPHA](_ALPHA), [_SETALPHA](_SETALPHA)
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* [_RGBA](_RGBA), [_RGBA32](_RGBA32) (set color with alpha)
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* [_RED](_RED), [_GREEN](_GREEN), [_BLUE](_BLUE)
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* [_RED32](_RED32), [_GREEN32](_GREEN32). [_BLUE32](_BLUE32)
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* [_CLEARCOLOR](_CLEARCOLOR), [_CLEARCOLOR (function)](_CLEARCOLOR-(function))
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* [Images](Images)
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