Rgba

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RGBA

Returns a colour value from red, green, blue and alpha parts of 0 to 255.

Syntax

#define RGBA(r,g,b,a) CULng((CUByte(r) Shl 16) Or (CUByte(g) Shl 8) Or CUByte(b) Or (CUByte(a) Shl 24))

Parameters

• red
• green
• blue
• alpha

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 long, 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.

Return Value

the combined color

Remarks

Usage

result = RGBA(red, green, blue, alpha)

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

Examples

'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 ) ( 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 UByte 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 = 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

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Category: 2D Drawing Functions
Kind: keyword

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.