mirror of
https://github.com/QB64Official/qb64.git
synced 2024-09-28 11:17:47 +00:00
103 lines
2.7 KiB
Markdown
103 lines
2.7 KiB
Markdown
The [_DONTBLEND](_DONTBLEND) statement turns off 32 bit alpha blending for the current image or screen mode where [_BLEND](_BLEND) is default.
|
|
|
|
## Syntax
|
|
|
|
> [_DONTBLEND](_DONTBLEND) [imageHandle&]
|
|
|
|
## Parameter(s)
|
|
|
|
* If imageHandle& is omitted, it is assumed to be the current [_DEST](_DEST)ination write page.
|
|
|
|
## Description
|
|
|
|
* If imageHandle& is not valid, an [ERROR Codes](ERROR-Codes) error will occur.
|
|
* [_DONTBLEND](_DONTBLEND) is faster than the default [_BLEND](_BLEND). **You may want to disable it**, unless you really need to use it in 32 bit.
|
|
* **32 bit screen surface backgrounds (black) have zero [_ALPHA](_ALPHA) so that they are transparent when placed over other surfaces.**
|
|
* Use [CLS](CLS) to make a new surface background [_ALPHA](_ALPHA) 255 or opaque.
|
|
* Both [_SOURCE](_SOURCE) and [_DEST](_DEST) must have [_BLEND](_BLEND) enabled, or else colors will NOT blend.
|
|
|
|
## Example(s)
|
|
|
|
Use _DONTBLEND when you want the 32 bit screen surface to be opaque so that it covers up other backgrounds. [CLS](CLS) works too.
|
|
|
|
```vb
|
|
|
|
SCREEN _NEWIMAGE(1280, 720, 32)
|
|
'CLS
|
|
_DONTBLEND '<<< comment out to see the difference
|
|
|
|
LINE (100, 100)-(500, 500), _RGB32(255, 255, 0), BF
|
|
|
|
b& = SaveBackground&
|
|
|
|
PRINT "This is just test junk"
|
|
PRINT
|
|
PRINT "Hit any key and the text should disappear, leaving us our pretty yellow box."
|
|
SLEEP
|
|
RestoreBackground b&
|
|
|
|
END
|
|
|
|
FUNCTION SaveBackground&
|
|
SaveBackground& = _COPYIMAGE(0)
|
|
END FUNCTION
|
|
|
|
SUB RestoreBackground (Image AS LONG)
|
|
_PUTIMAGE , Image, 0
|
|
END SUB
|
|
|
|
```
|
|
|
|
Turning off blending to create transparency.
|
|
|
|
```vb
|
|
|
|
SCREEN _NEWIMAGE(640, 480, 32)
|
|
alphaSprite& = _NEWIMAGE(64, 64, 32)
|
|
|
|
_DONTBLEND alphaSprite& ' turn off alpha-blending
|
|
|
|
'Create a simple sprite with transparency
|
|
_DEST alphaSprite&
|
|
FOR y = 0 TO 63
|
|
FOR x = 0 TO 63
|
|
alpha = SQR((x - 32) ^ 2 + (y - 32) ^ 2) / 32
|
|
IF alpha < 0 THEN alpha = 0
|
|
alpha = (1 - alpha * alpha) 'parabolic curve
|
|
PSET (x, y), _RGBA32(255, 255, 255, alpha * 255)
|
|
NEXT
|
|
NEXT
|
|
|
|
'Make a simple background texture
|
|
_DEST 0
|
|
FOR y = 1 TO 479
|
|
FOR x = 0 TO 639
|
|
PSET (x, y), _RGB32(x AND 255, y AND 255, (x XOR y) AND 255)
|
|
NEXT
|
|
NEXT
|
|
|
|
'Store background so we can show moveable objects on it
|
|
background& = _COPYIMAGE
|
|
|
|
'Treat my alpha values as transparency
|
|
_BLEND alphaSprite&
|
|
|
|
ph = 0
|
|
DO: _LIMIT 60
|
|
x = 320 - 250 * COS(ph) - (_WIDTH(alphaSprite&) \ 2)
|
|
y = 240 - 150 * COS(ph * 1.3) - (_HEIGHT(alphaSprite&) \ 2)
|
|
ph = ph + 0.03
|
|
_PUTIMAGE , background&, 0
|
|
_PUTIMAGE (x, y), alphaSprite&, 0
|
|
_DISPLAY
|
|
LOOP UNTIL LEN(INKEY$)
|
|
|
|
```
|
|
|
|
*Explanation:* To make the alpha image, turn alpha blending off. Otherwise PSET blends the pixel to instead of making the sprite transparent.
|
|
|
|
## See Also
|
|
|
|
* [_BLEND](_BLEND)
|
|
* [_BLEND (function)](_BLEND-(function))
|
|
* [Images](Images)
|