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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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104 lines
3.4 KiB
Plaintext
104 lines
3.4 KiB
Plaintext
{{DISPLAYTITLE:_DONTBLEND}}
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The [[_DONTBLEND]] statement turns off 32 bit alpha blending for the current image or screen mode where [[_BLEND]] is default.
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{{PageSyntax}}
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: [[_DONTBLEND]] [{{Parameter|imageHandle&}}]
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{{Parameters}}
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* If {{Parameter|imageHandle&}} is omitted, it is assumed to be the current [[_DEST]]ination write page.
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{{PageDescription}}
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* If {{Parameter|imageHandle&}} is not valid, an [[ERROR Codes|Invalid handle]] error will occur.
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* [[_DONTBLEND]] is faster than the default [[_BLEND]]. '''You may want to disable it''', unless you really need to use it in 32 bit.
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* '''32 bit screen surface backgrounds (black) have zero [[_ALPHA]] so that they are transparent when placed over other surfaces.'''
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* Use [[CLS]] to make a new surface background [[_ALPHA]] 255 or opaque.
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* Both [[_SOURCE]] and [[_DEST]] must have [[_BLEND]] enabled, or else colors will NOT blend.
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{{PageExamples}}
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''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.
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{{CodeStart}} '' ''
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{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(1280, 720, 32)
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'{{Cl|CLS}}
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{{Cl|_DONTBLEND}} '<<< comment out to see the difference
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{{Cl|LINE}} (100, 100)-(500, 500), {{Cl|_RGB32}}(255, 255, 0), BF
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b& = SaveBackground&
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{{Cl|PRINT}} "This is just test junk"
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{{Cl|PRINT}}
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{{Cl|PRINT}} "Hit any key and the text should disappear, leaving us our pretty yellow box."
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{{Cl|SLEEP}}
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RestoreBackground b&
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{{Cl|END}}
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{{Cl|FUNCTION}} SaveBackground&
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SaveBackground& = {{Cl|_COPYIMAGE}}(0)
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{{Cl|END FUNCTION}}
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{{Cl|SUB}} RestoreBackground (Image {{Cl|AS}} {{Cl|LONG}})
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{{Cl|_PUTIMAGE}} , Image, 0
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{{Cl|END SUB}} '' ''
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{{CodeEnd}}
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''Example 2:'' Turning off blending to create transparency.
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{{CodeStart}}
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{{Cl|SCREEN (statement)|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)
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alphaSprite& = {{Cl|_NEWIMAGE}}(64, 64, 32)
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{{Cl|_DONTBLEND}} alphaSprite& ' turn off alpha-blending
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'Create a simple sprite with transparency
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{{Cl|_DEST}} alphaSprite&
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{{Cl|FOR}} y = 0 {{Cl|TO}} 63
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{{Cl|FOR}} x = 0 {{Cl|TO}} 63
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alpha = {{Cl|SQR}}((x - 32) ^ 2 + (y - 32) ^ 2) / 32
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{{Cl|IF}} alpha < 0 {{Cl|THEN}} alpha = 0
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alpha = (1 - alpha * alpha) 'parabolic curve
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{{Cl|PSET}} (x, y), {{Cl|_RGBA32}}(255, 255, 255, alpha * 255)
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{{Cl|NEXT}}
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{{Cl|NEXT}}
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'Make a simple background texture
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{{Cl|_DEST}} 0
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{{Cl|FOR}} y = 1 {{Cl|TO}} 479
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{{Cl|FOR}} x = 0 {{Cl|TO}} 639
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{{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)
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{{Cl|NEXT}}
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{{Cl|NEXT}}
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'Store background so we can show moveable objects on it
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background& = {{Cl|_COPYIMAGE}}
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'Treat my alpha values as transparency
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{{Cl|_BLEND}} alphaSprite&
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ph = 0
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{{Cl|DO}}: {{Cl|_LIMIT}} 60
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x = 320 - 250 * {{Cl|COS}}(ph) - ({{Cl|_WIDTH (function)|_WIDTH}}(alphaSprite&) \ 2)
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y = 240 - 150 * {{Cl|COS}}(ph * 1.3) - ({{Cl|_HEIGHT}}(alphaSprite&) \ 2)
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ph = ph + 0.03
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{{Cl|_PUTIMAGE}} , background&, 0
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{{Cl|_PUTIMAGE}} (x, y), alphaSprite&, 0
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{{Cl|_DISPLAY}}
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{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|LEN}}({{Cl|INKEY$}}) '' ''
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{{CodeEnd}}{{small|Code by Zom-B}}
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''Explanation:'' To make the alpha image, turn alpha blending off. Otherwise PSET blends the pixel to instead of making the sprite transparent.
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{{PageSeeAlso}}
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* [[_BLEND]]
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* [[_BLEND (function)]]
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* [[Images]]
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{{PageNavigation}}
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<
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