DONTBLEND: Difference between revisions

From QB64 Phoenix Edition Wiki
Jump to navigation Jump to search
No edit summary
No edit summary
 
(2 intermediate revisions by the same user not shown)
Line 22: Line 22:
''Example 1:'' Use _DONTBLEND when you want the 32 bit screen surface to be opaque so that it covers up other backgrounds. [[CLS]] works too.
''Example 1:'' Use _DONTBLEND when you want the 32 bit screen surface to be opaque so that it covers up other backgrounds. [[CLS]] works too.
{{CodeStart}}
{{CodeStart}}
{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(1280, 720, 32)
{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}({{Text|1280|#F580B1}}, {{Text|720|#F580B1}}, {{Text|32|#F580B1}})
'{{Cl|CLS}}
{{Text|<nowiki>'CLS</nowiki>|#919191}}
{{Cl|_DONTBLEND}} '<<< comment out to see the difference
{{Cl|_DONTBLEND}} {{Text|<nowiki>'<<< comment out to see the difference</nowiki>|#919191}}


{{Cl|LINE}} (100, 100)-(500, 500), {{Cl|_RGB32}}(255, 255, 0), BF
{{Cl|LINE}} ({{Text|100|#F580B1}}, {{Text|100|#F580B1}})-({{Text|500|#F580B1}}, {{Text|500|#F580B1}}), {{Cl|_RGB32}}({{Text|255|#F580B1}}, {{Text|255|#F580B1}}, {{Text|0|#F580B1}}), BF


b& = SaveBackground&
b& = {{Text|SaveBackground&|#55FF55}}


{{Cl|PRINT}} "This is just test junk"
{{Cl|PRINT}} {{Text|<nowiki>"This is just test junk"</nowiki>|#FFB100}}
{{Cl|PRINT}}
{{Cl|PRINT}}
{{Cl|PRINT}} "Hit any key and the text should disappear, leaving us our pretty yellow box."
{{Cl|PRINT}} {{Text|<nowiki>"Hit any key and the text should disappear, leaving us our pretty yellow box."</nowiki>|#FFB100}}
{{Cl|SLEEP}}
{{Cl|SLEEP}}
RestoreBackground b&
{{Text|RestoreBackground|#55FF55}} b&


{{Cl|END}}
{{Cl|END}}


{{Cl|FUNCTION}} SaveBackground&
{{Cl|FUNCTION}} {{Text|SaveBackground&|#55FF55}}
SaveBackground& = {{Cl|_COPYIMAGE}}(0)
    {{Text|SaveBackground&|#55FF55}} = {{Cl|_COPYIMAGE}}({{Text|0|#F580B1}})
{{Cl|END FUNCTION}}
{{Cl|END FUNCTION}}


{{Cl|SUB}} RestoreBackground (Image {{Cl|AS}} {{Cl|LONG}})
{{Cl|SUB}} {{Text|RestoreBackground|#55FF55}} (Image {{Cl|AS}} {{Cl|LONG}})
{{Cl|_PUTIMAGE}} , Image, 0
    {{Cl|_PUTIMAGE}} , Image, {{Text|0|#F580B1}}
{{Cl|END SUB}}
{{Cl|END SUB}}
{{CodeEnd}}
{{CodeEnd}}


----


''Example 2:'' Turning off blending to create transparency.
''Example 2:'' Turning off blending to create transparency.
{{CodeStart}}
{{CodeStart}}
{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}({{Text|640|#F580B1}}, {{Text|480|#F580B1}}, {{Text|32|#F580B1}})
alphaSprite& = {{Cl|_NEWIMAGE}}({{Text|64|#F580B1}}, {{Text|64|#F580B1}}, {{Text|32|#F580B1}})


{{Cl|SCREEN (statement)|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)
{{Cl|_DONTBLEND}} alphaSprite& {{Text|<nowiki>' turn off alpha-blending</nowiki>|#919191}}
alphaSprite& = {{Cl|_NEWIMAGE}}(64, 64, 32)


{{Cl|_DONTBLEND}} alphaSprite&  ' turn off alpha-blending
{{Text|<nowiki>'Create a simple sprite with transparency</nowiki>|#919191}}
 
'Create a simple sprite with transparency
{{Cl|_DEST}} alphaSprite&
{{Cl|_DEST}} alphaSprite&
{{Cl|FOR}} y = 0 {{Cl|TO}} 63
{{Cl|FOR}} y = {{Text|0|#F580B1}} {{Cl|TO}} {{Text|63|#F580B1}}
  {{Cl|FOR}} x = 0 {{Cl|TO}} 63
    {{Cl|FOR}} x = {{Text|0|#F580B1}} {{Cl|TO}} {{Text|63|#F580B1}}
    alpha = {{Cl|SQR}}((x - 32) ^ 2 + (y - 32) ^ 2) / 32
        alpha = {{Cl|SQR}}((x - {{Text|32|#F580B1}}) ^ {{Text|2|#F580B1}} + (y - {{Text|32|#F580B1}}) ^ {{Text|2|#F580B1}}) / {{Text|32|#F580B1}}
    {{Cl|IF}} alpha < 0 {{Cl|THEN}} alpha = 0
        {{Cl|IF}} alpha < {{Text|0|#F580B1}} {{Cl|THEN}} alpha = {{Text|0|#F580B1}}
    alpha = (1 - alpha * alpha) 'parabolic curve
        alpha = ({{Text|1|#F580B1}} - alpha * alpha) {{Text|<nowiki>'parabolic curve</nowiki>|#919191}}
    {{Cl|PSET}} (x, y), {{Cl|_RGBA32}}(255, 255, 255, alpha * 255)
        {{Cl|PSET}} (x, y), {{Cl|_RGBA32}}({{Text|255|#F580B1}}, {{Text|255|#F580B1}}, {{Text|255|#F580B1}}, alpha * {{Text|255|#F580B1}})
  {{Cl|NEXT}}
    {{Cl|NEXT}}
{{Cl|NEXT}}
{{Cl|NEXT}}


'Make a simple background texture
{{Text|<nowiki>'Make a simple background texture</nowiki>|#919191}}
{{Cl|_DEST}} 0
{{Cl|_DEST}} {{Text|0|#F580B1}}
{{Cl|FOR}} y = 1 {{Cl|TO}} 479
{{Cl|FOR}} y = {{Text|1|#F580B1}} {{Cl|TO}} {{Text|479|#F580B1}}
  {{Cl|FOR}} x = 0 {{Cl|TO}} 639
    {{Cl|FOR}} x = {{Text|0|#F580B1}} {{Cl|TO}} {{Text|639|#F580B1}}
    {{Cl|PSET}} (x, y), {{Cl|_RGB32}}(x {{Cl|AND (boolean)|AND}} 255, y {{Cl|AND (boolean)|AND}} 255, (x {{Cl|XOR (boolean)|XOR}} y) {{Cl|AND (boolean)|AND}} 255)
        {{Cl|PSET}} (x, y), {{Cl|_RGB32}}(x {{Cl|AND}} {{Text|255|#F580B1}}, y {{Cl|AND}} {{Text|255|#F580B1}}, (x {{Cl|XOR}} y) {{Cl|AND}} {{Text|255|#F580B1}})
  {{Cl|NEXT}}
    {{Cl|NEXT}}
{{Cl|NEXT}}
{{Cl|NEXT}}


'Store background so we can show moveable objects on it
{{Text|<nowiki>'Store background so we can show moveable objects on it</nowiki>|#919191}}
background& = {{Cl|_COPYIMAGE}}
background& = {{Cl|_COPYIMAGE}}({{Text|0|#F580B1}})


'Treat my alpha values as transparency
{{Text|<nowiki>'Treat my alpha values as transparency</nowiki>|#919191}}
{{Cl|_BLEND}} alphaSprite&
{{Cl|_BLEND}} alphaSprite&


ph = 0
ph = {{Text|0|#F580B1}}
{{Cl|DO}}: {{Cl|_LIMIT}} 60
{{Cl|DO}}: {{Cl|_LIMIT}} {{Text|60|#F580B1}}
  x = 320 - 250 * {{Cl|COS}}(ph) - ({{Cl|_WIDTH (function)|_WIDTH}}(alphaSprite&) \ 2)
    x = {{Text|320|#F580B1}} - {{Text|250|#F580B1}} * {{Cl|COS}}(ph) - ({{Cl|_WIDTH (function)|_WIDTH}}(alphaSprite&) \ {{Text|2|#F580B1}})
  y = 240 - 150 * {{Cl|COS}}(ph * 1.3) - ({{Cl|_HEIGHT}}(alphaSprite&) \ 2)
    y = {{Text|240|#F580B1}} - {{Text|150|#F580B1}} * {{Cl|COS}}(ph * {{Text|1.3|#F580B1}}) - ({{Cl|_HEIGHT}}(alphaSprite&) \ {{Text|2|#F580B1}})
  ph = ph + 0.03
    ph = ph + {{Text|0.03|#F580B1}}
  {{Cl|_PUTIMAGE}} , background&, 0
    {{Cl|_PUTIMAGE}} , background&, {{Text|0|#F580B1}}
  {{Cl|_PUTIMAGE}} (x, y), alphaSprite&, 0
    {{Cl|_PUTIMAGE}} (x, y), alphaSprite&, {{Text|0|#F580B1}}
  {{Cl|_DISPLAY}}
    {{Cl|_DISPLAY}}
{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|LEN}}({{Cl|INKEY$}})
{{Cl|DO...LOOP|LOOP UNTIL}} {{Cl|LEN}}({{Cl|INKEY$}})
{{CodeEnd}}{{small|Code by Zom-B}}
{{CodeEnd}}
{{Small|Code by Zom-B}}
''Explanation:'' To make the alpha image, turn alpha blending off. Otherwise PSET blends the pixel to instead of making the sprite transparent.
''Explanation:'' To make the alpha image, turn alpha blending off. Otherwise PSET blends the pixel to instead of making the sprite transparent.


Latest revision as of 10:46, 24 March 2023

The _DONTBLEND statement turns off 32 bit alpha blending for the current image or screen mode where _BLEND is default.


Syntax

_DONTBLEND [imageHandle&]


Parameters

  • If imageHandle& is omitted, it is assumed to be the current _DESTination write page.


Description

  • If imageHandle& is not valid, an Invalid handle error will occur.
  • _DONTBLEND is faster than the default _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 so that they are transparent when placed over other surfaces.
  • Use CLS to make a new surface background _ALPHA 255 or opaque.
  • Both _SOURCE and _DEST must have _BLEND enabled, or else colors will NOT blend.


Examples

Example 1: Use _DONTBLEND when you want the 32 bit screen surface to be opaque so that it covers up other backgrounds. CLS works too. 

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

Example 2: Turning off blending to create transparency. 

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(0)

'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$)
Code by Zom-B

Explanation: To make the alpha image, turn alpha blending off. Otherwise PSET blends the pixel to instead of making the sprite transparent.


See also


Navigation:
Main Page with Articles and Tutorials
Keyword Reference - Alphabetical
Keyword Reference - By usage
Report a broken link
Retrieved from "https://qb64phoenix.com/qb64wiki/index.php?title=DONTBLEND&oldid=8315"