_ALPHA32 - mkilgore/QB64pe GitHub Wiki

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

alpha& = _ALPHA32(color32~&)

• color32& 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).

• In 4-bit (16 colors) or 8-bit (256 colors) 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.

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

COLOR clr~&
PRINT "Alpha32:"; _ALPHA32(clr~&)

END '' ''

<span style="color:#FFFFFF;">Color: 3237937407</span>
<span style="color:#FF00FF;">Alpha32: 192</span>

Notes: The color value is equivalent to hexadecimal &HC0FF00FF where &HC0 equals 192. _RGB alphas are always &HFF(255).

• _ALPHA, _SETALPHA
• _RGBA, _RGBA32 (set color with alpha)
• _RED, _GREEN, _BLUE
• _RED32, _GREEN32. _BLUE32
• _CLEARCOLOR, _CLEARCOLOR (function)
• Images