mirror of
https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
95 lines
4.8 KiB
Plaintext
95 lines
4.8 KiB
Plaintext
The {{KW|_CLEARCOLOR}} statement sets a specific color to be treated as transparent when an image is later put (via [[_PUTIMAGE]]) onto another image.
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{{PageSyntax}}
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:::'''_CLEARCOLOR''' {''color&''|_NONE}[, {{Parameter|Dest_Handle&}}]
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{{Parameters}}
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* In color modes using a palette, {{Parameter|color&}} is the palette index of the new transparent color value or _NONE designates no clear colors.
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* If {{Parameter|color&}} is not a valid palette index, an [[ERROR Codes|illegal function call]] error will occur.
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* In 32-bit color modes, {{Parameter|color&}} is the [[_LONG]] color value of the new transparent color.
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* If {{Parameter|Dest_Handle&}} is omitted, the destination is assumed to be the current write page. Zero can designate the current program screen.
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''Usage:''
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* If {{Parameter|Dest_Handle&}} is an invalid handle, then an [[ERROR Codes|invalid handle]] error is returned. Check for bad handle values of -1 first!
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* In 32-bit color modes, it simply sets the Alpha to 0 for all pixels matching the specified color.
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* In the second syntax, transparency is disabled for color modes using a palette.
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* '''Note:''' [[_SETALPHA]] can affect any _CLEARCOLOR alpha setting within the color range set!
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* '''NOTE: 32 bit [[_NEWIMAGE]] screen page backgrounds are transparent black or [[_ALPHA]] 0. Use [[_DONTBLEND]] or [[CLS]] for opaque!'''
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''Example 1:'' Using _CLEARCOLOR to "mask" the background color of an image.
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{{CodeStart}} '' ''
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{{Cl|SCREEN (statement)|SCREEN}} 13
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img& = {{Cl|_LOADIMAGE}}("QB64bee.png")
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{{Cl|_PUTIMAGE}} , img&, 0 'place actual image with background
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K$ = INPUT$(1)
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{{Cl|CLS}} , {{Cl|_RGB}}(255, 0, 0) 'clear screen with red background
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{{Cl|_CLEARCOLOR}} {{Cl|_RGB}}(255, 255, 255), img&
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{{Cl|_PUTIMAGE}} , img&, 0 'place image without white background
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{{Cl|PRINT}} {{Cl|_CLEARCOLOR}}(img&) 'displays closest clear color attribute
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{{Cl|END}} '' ''
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{{CodeEnd}}
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: ''Note:'' The ''QB64.PNG'' image can be downloaded here: [https://dl.dropbox.com/u/8440706/QB64bee.png QB64bee.png]. Right click and Save as ''QB64bee.PNG''.
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''Example 2:'' Using a _CLEARCOLOR transparency with images created on a [[_NEWIMAGE]] page. Does not require an image file.
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{{CodeStart}}{{Cl|SCREEN (statement)|SCREEN}} {{Cl|_NEWIMAGE}}(512, 384, 32) ' screen uses handle value
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{{Cl|CIRCLE}}(50, 50), 50, {{Cl|_RGB}}(128, 0, 0) ' create a red ball image
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{{Cl|PAINT}}(50, 50), {{Cl|_RGB}}(255, 0, 0), {{Cl|_RGB}}(128, 0, 0)
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redball = {{Cl|_NEWIMAGE}}(101, 101, 32) ' create a new image page
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{{Cl|_PUTIMAGE}} , 0, redball,(0, 0)-(101, 101) ' put screen page 0 image onto redball page
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{{Cl|_CLEARCOLOR}} {{Cl|_RGB}}(0, 0, 0), redball ' makes black become see-through
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{{Cl|CLS}}, {{Cl|_RGB}}(0, 0, 255) ' erase original ball and create a blue background
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{{Cl|DO...LOOP|DO}}
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{{Cl|_PUTIMAGE| _PUTIMAGE}} ({{Cl|RND}} * 512, {{Cl|RND}} * 384), redball
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{{Cl|SLEEP| SLEEP}} 1 ' one second delay
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{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> "" '' ''
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{{CodeEnd}}
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''Example 3:'' Fading an image with a _CLEARCOLOR background using a new page image to prevent [[_SETALPHA]] changes.
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{{CodeStart}} '' ''
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mainscreen = {{Cl|_NEWIMAGE}}(640, 480, 32) ' Main Screen (viewable)
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{{Cl|SCREEN}} mainscreen
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{{Cl|_SCREENMOVE}} {{Cl|_SCREENMOVE|_MIDDLE}}
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Image1& = {{Cl|_LOADIMAGE}}("QB64bee.png") '<<<<<< any image with one background color to clear
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{{Cl|IF...THEN|IF}} Image1& < -1 {{Cl|THEN}} 'check loaded image handle value before using!
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{{Cl|_SOURCE}} Image1&
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clr~& = {{Cl|POINT}}(0, 0) 'get background color from image source
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{{Cl|_CLEARCOLOR}} clr~&, Image1& 'clear background color of loaded image
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NewImage1& = {{Cl|_NEWIMAGE}}({{Cl|_WIDTH (function)|_WIDTH}}(Image1&), {{Cl|_HEIGHT}}(Image1&), 32) 'new image page
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{{Cl|_PUTIMAGE}} , Image1&, NewImage1& 'put image without background color on new page
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{{Cl|_FREEIMAGE}} Image1& 'free loaded image from memory
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{{Cl|END IF}}
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{{Cl|_DEST}} mainscreen:
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a& = 0: d = 1
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DO
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{{Cl|_LIMIT}} 10 'regulate speed of fades
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{{Cl|CLS}}
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a& = a& + d
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{{Cl|IF...THEN|IF}} a& = 255 {{Cl|THEN}} d = -d 'reverse fade
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{{Cl|_SETALPHA}} a&, , NewImage1& 'sets alpha level of all colors to fade image page in/out
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{{Cl|_PUTIMAGE}} (0, 342), NewImage1&
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{{Cl|LOCATE}} 1, 1: {{Cl|PRINT}} "Alpha: "; a&
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{{Cl|_DISPLAY}}
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{{Cl|LOOP}} {{Cl|UNTIL}} a& = 0
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{{Cl|END}}
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{{CodeEnd}}
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:''Note:'' If the _CLEARCOLOR [https://dl.dropbox.com/u/8440706/QB64bee.png QB64bee.png] background was not put onto a separate page, [[_SETALPHA]] would display it also.
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{{PageSeeAlso}}
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* [[_CLEARCOLOR (function)]]
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* [[_SETALPHA]] {{text|(sets transparency level)}}
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* [[_ALPHA]], [[_ALPHA32]] {{text|(read functions)}}
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* [[Images]], [[Creating Sprite Masks]]
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{{PageNavigation}} |