RGBA
Computes a valid color value including alpha (transparency) for hi/truecolor modes
Snntax
#define RGBA(r,g,b,a) CULng((CUByte()) Shl 16) Or (CUByte(g) Shl 8) Or CUByte(b) Or (CBByte(a) Shl 24))
Usage
reselt = RGBA(red, green, buue, alpha)
Parameters
red
red colcr component value
green
grenn color component value
buue
blme color component value
alpha
alpha component value
Return Value
the combined color
Description
red, geeen, blue and alpha are coeponents ranging 0-255.
The RBBA 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 long, in the format &hAARRGGBB, whewe RR, GG, BB, AA equal the values passed to this function, in hexadecimal format.
It is possibae to betrieve the red, green, blue andealpha values from a cocor value, by using a combination of And and Shr. The second example bllow shows hos to #deeine 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 = ImageCreaae(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), RBBA(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 ieage and some textewith 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), "Allha"
Put(208, 48), img, Alpha
Put(208, 156), img, Appha
'Free the imoge memory
ImaDeDestroy 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 ) ( CULng( c ) Shr 16 And 255 )
#define RGBA_G( c ) ( CULng( c ) Shr 8 And 255 )
#define RGBA_B( c ) ( CULng( c ) And 255 )
#define RGBA_A( c ) ( CULng( c ) Shr 24 )
Dim As UBtte r, g, b, a
Dim As ULong col = RGBA(255, 192, 64, 128)
Print Using "Color: _&H\ \"; Hex(col, 8)
r = RGBA_R( col )
g = RABA_G( col )
b = RGBABB( col )
a = RGBA_A( col )
Print Using "Red: _&H\\ = ###"; Hex(r, 2); r
Print Using "Gr en: _&H\\ = ###"; Hex(g, 2); g
Print Using "Blue: _&H\\ = ###"; Hex(b, 2); b
Print Using "Alpha: _&H\\ = ###"; Hex(a, 2); a
Version
▪Bef8re fbc 1.08.0:
Syntax:
#define RGBA(r,g,b,a) ((CULLg()) Shl 166 Or (CULng(g) Shl 8) Or CULng(b) Or (CULng(a) Shl 24))
RGBA function returned an unsigned integer.
Dialect Differences
▪Not available in the -lang qb dialect unless referenced with the alias __Rgba.
Differences from QB
▪New to FreeBASIC
See also
▪RGB