DONTBLEND: Difference between revisions

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{{Parameters}}
{{PageParameters}}
* If {{Parameter|imageHandle&}} is omitted, it is assumed to be the current [[_DEST]]ination write page.
* If {{Parameter|imageHandle&}} is omitted, it is assumed to be the current [[_DEST]]ination write page.


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
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