RGBA
Computes a valid color value including alpha (transparency) for hi/truecolor modes
Syntax
`
#define RGBA(r,g,b,a) ((CUInt(r) Shl 16) Or (CUInt(g) Shl 8) Or CUInt(b) Or (CUInt(a) Shl 24))
`
Usage
`
result = RGBA(red, green, blue, alpha)
`
Parameters
`red`
red color component value
`green`
green color component value
`blue`
blue color component value
`alpha`
alpha component value
Return Value
the combined color
Description
`red`, `green`, `blue` and `alpha` are components ranging `0`-`255`.
The `RGBA` function can be used to compute a valid color value including an alpha channel for use while in hi/truecolor modes. It returns an unsigned integer in the format `&hAARRGGBB`, where `RR`, `GG`, `BB`, `AA` equal the values passed to this function, in hexadecimal format.
It is possible to retrieve the red, green, blue and alpha values from a color value, by using a combination of `And` and `Shr`. The second example below shows how to `#define` and use macros to do this.
Example
`
'open a graphics screen (320 * 240, 32-bit)
ScreenRes 320, 240, 32
Dim As Any Ptr img
Dim As Integer x, y
'make an image that varies in transparency and color
img = ImageCreate(64, 64)
For x = 0 To 63
For y = 0 To 63
PSet img, (x, y), RGBA(x * 4, 0, y * 4, (x + y) * 2)
Next y
Next x
Circle img, (31, 31), 25, RGBA(0, 127, 192, 192), ,,, F 'semi-transparent blue circle
Line img, (26, 20)-(38, 44), RGBA(255, 255, 255, 0), BF 'transparent white rectangle
'draw a background (diagonal white lines)
For x = -240 To 319 Step 10
Line (x, 0)-Step(240, 240), RGB(255, 255, 255)
Next
Line (10, 10)-(310, 37), RGB(127, 0, 0), BF 'red box for text
Line (10, 146)-(310, 229), RGB(0, 127, 0), BF 'green box for Putting onto
'draw the image and some text with PSET
Draw String(64, 20), "PSet"
Put(48, 48), img, PSet
Put(48, 156), img, PSet
'draw the image and some text with ALPHA
Draw String (220, 20), "Alpha"
Put(208, 48), img, Alpha
Put(208, 156), img, Alpha
'Free the image memory
ImageDestroy img
'Keep the window open until the user presses a key
Sleep
`
`
'' setting and retrieving Red, Green, Blue and Alpha values
#define RGBA_R( c ) ( CUInt( c ) Shr 16 And 255 )
#define RGBA_G( c ) ( CUInt( c ) Shr 8 And 255 )
#define RGBA_B( c ) ( CUInt( c ) And 255 )
#define RGBA_A( c ) ( CUInt( c ) Shr 24 )
Dim As UInteger r, g, b, a
Dim As UInteger col = RGBA(255, 192, 64, 128)
Print Using "Color: _&H\ \"; Hex(col, 8)
r = RGBA_R( col )
g = RGBA_G( col )
b = RGBA_B( col )
a = RGBA_A( col )
Print
Print Using "Red: _&H\\ = ###"; Hex(r, 2); r
Print Using "Green: _&H\\ = ###"; Hex(g, 2); g
Print Using "Blue: _&H\\ = ###"; Hex(b, 2); b
Print Using "Alpha: _&H\\ = ###"; Hex(a, 2); a
`
Dialect Differences

- Not available in the -lang qb dialect unless referenced with the alias `__Rgba`.

Differences from QB

- New to FreeBASIC

See also

- `RGB`
- `Color`
- `#define`