CLEARCOLOR: Difference between revisions
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{{DISPLAYTITLE:_CLEARCOLOR}} | {{DISPLAYTITLE:_CLEARCOLOR}} | ||
The [[_CLEARCOLOR]] statement sets a specific color to be treated as transparent when an image is later put (via [[_PUTIMAGE]]) onto another image. | The [[_CLEARCOLOR]] statement sets a specific color to be treated as transparent when an image is later put (via [[_PUTIMAGE]]) onto another image. | ||
{|align="right" | {|align="right" | ||
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{{PageExamples}} | {{PageExamples}} | ||
''Example 1:'' Using _CLEARCOLOR to "mask" the background color of an image. | ''Example 1:'' Using _CLEARCOLOR to "mask" the background color of an image. | ||
{{CodeStart}} | {{CodeStart}} | ||
{{Cl|SCREEN (statement)|SCREEN}} 13 | {{Cl|SCREEN (statement)|SCREEN}} 13 | ||
img& = {{Cl|_LOADIMAGE}}("qb64_trans.png") | img& = {{Cl|_LOADIMAGE}}("qb64_trans.png") | ||
Line 35: | Line 35: | ||
{{Cl|_PUTIMAGE}} , img&, 0 'place image without white background | {{Cl|_PUTIMAGE}} , img&, 0 'place image without white background | ||
{{Cl|PRINT}} {{Cl|_CLEARCOLOR}}(img&) 'displays closest clear color attribute | {{Cl|PRINT}} {{Cl|_CLEARCOLOR}}(img&) 'displays closest clear color attribute | ||
{{Cl|END}} | {{Cl|END}} | ||
{{CodeEnd}} | {{CodeEnd}} | ||
Line 50: | Line 50: | ||
{{Cl|_PUTIMAGE| _PUTIMAGE}} ({{Cl|RND}} * 512, {{Cl|RND}} * 384), redball | {{Cl|_PUTIMAGE| _PUTIMAGE}} ({{Cl|RND}} * 512, {{Cl|RND}} * 384), redball | ||
{{Cl|SLEEP| SLEEP}} 1 ' one second delay | {{Cl|SLEEP| SLEEP}} 1 ' one second delay | ||
{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> "" | {{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> "" | ||
{{CodeEnd}} | {{CodeEnd}} | ||
''Example 3:'' Fading an image with a _CLEARCOLOR background using a new page image to prevent [[_SETALPHA]] changes. | ''Example 3:'' Fading an image with a _CLEARCOLOR background using a new page image to prevent [[_SETALPHA]] changes. | ||
{{CodeStart}} | {{CodeStart}} | ||
mainscreen = {{Cl|_NEWIMAGE}}(640, 480, 32) ' Main Screen (viewable) | mainscreen = {{Cl|_NEWIMAGE}}(640, 480, 32) ' Main Screen (viewable) | ||
{{Cl|SCREEN}} mainscreen | {{Cl|SCREEN}} mainscreen | ||
Line 76: | Line 76: | ||
{{Cl|CLS}} | {{Cl|CLS}} | ||
a& = a& + d | a& = a& + d | ||
{{Cl|IF...THEN|IF}} a& = 255 {{Cl|THEN}} d = -d 'reverse fade | {{Cl|IF...THEN|IF}} a& = 255 {{Cl|THEN}} d = -d 'reverse fade | ||
{{Cl|_SETALPHA}} a&, , NewImage1& 'sets alpha level of all colors to fade image page in/out | {{Cl|_SETALPHA}} a&, , NewImage1& 'sets alpha level of all colors to fade image page in/out | ||
{{Cl|_PUTIMAGE}} (0, 342), NewImage1& | {{Cl|_PUTIMAGE}} (0, 342), NewImage1& | ||
{{Cl|LOCATE}} 1, 1: {{Cl|PRINT}} "Alpha: "; a& | {{Cl|LOCATE}} 1, 1: {{Cl|PRINT}} "Alpha: "; a& | ||
{{Cl|_DISPLAY}} | {{Cl|_DISPLAY}} |
Revision as of 01:14, 23 January 2023
The _CLEARCOLOR statement sets a specific color to be treated as transparent when an image is later put (via _PUTIMAGE) onto another image.
Syntax
- _CLEARCOLOR {color&|_NONE}[, Dest_Handle&]
- In color modes using a palette, color& is the palette index of the new transparent color value or _NONE designates no clear colors.
- If color& is not a valid palette index, an illegal function call error will occur.
- In 32-bit color modes, color& is the _LONG color value of the new transparent color.
- If Dest_Handle& is omitted, the destination is assumed to be the current write page. Zero can designate the current program screen.
Description
- If Dest_Handle& is an invalid handle, then an invalid handle error is returned. Check for bad handle values of -1 first.
- In 32-bit color modes, it simply sets the Alpha to 0 for all pixels matching the specified color.
- In the second syntax, transparency is disabled for color modes using a palette.
- Note: _SETALPHA can affect any _CLEARCOLOR alpha setting within the color range set.
- NOTE: 32 bit _NEWIMAGE screen page backgrounds are transparent black or _ALPHA 0. Use _DONTBLEND or CLS for opaque.
Examples
Example 1: Using _CLEARCOLOR to "mask" the background color of an image.
SCREEN 13 img& = _LOADIMAGE("qb64_trans.png") _PUTIMAGE , img&, 0 'place actual image with background K$ = INPUT$(1) CLS , _RGB(255, 0, 0) 'clear screen with red background _CLEARCOLOR _RGB(255, 255, 255), img& _PUTIMAGE , img&, 0 'place image without white background PRINT _CLEARCOLOR(img&) 'displays closest clear color attribute END |
Example 2: Using a _CLEARCOLOR transparency with images created on a _NEWIMAGE page. Does not require an image file.
SCREEN _NEWIMAGE(512, 384, 32) ' screen uses handle value CIRCLE(50, 50), 50, _RGB(128, 0, 0) ' create a red ball image PAINT(50, 50), _RGB(255, 0, 0), _RGB(128, 0, 0) redball = _NEWIMAGE(101, 101, 32) ' create a new image page _PUTIMAGE , 0, redball,(0, 0)-(101, 101) ' put screen page 0 image onto redball page _CLEARCOLOR _RGB(0, 0, 0), redball ' makes black become see-through CLS, _RGB(0, 0, 255) ' erase original ball and create a blue background DO _PUTIMAGE (RND * 512, RND * 384), redball SLEEP 1 ' one second delay LOOP UNTIL INKEY$ <> "" |
Example 3: Fading an image with a _CLEARCOLOR background using a new page image to prevent _SETALPHA changes.
mainscreen = _NEWIMAGE(640, 480, 32) ' Main Screen (viewable) SCREEN mainscreen _SCREENMOVE _MIDDLE Image1& = _LOADIMAGE("qb64_trans.png") '<<<<<< any image with one background color to clear IF Image1& < -1 THEN 'check loaded image handle value before using! _SOURCE Image1& clr~& = POINT(0, 0) 'get background color from image source _CLEARCOLOR clr~&, Image1& 'clear background color of loaded image NewImage1& = _NEWIMAGE(_WIDTH(Image1&), _HEIGHT(Image1&), 32) 'new image page _PUTIMAGE , Image1&, NewImage1& 'put image without background color on new page _FREEIMAGE Image1& 'free loaded image from memory END IF _DEST mainscreen: a& = 0: d = 1 DO _LIMIT 10 'regulate speed of fades CLS a& = a& + d IF a& = 255 THEN d = -d 'reverse fade _SETALPHA a&, , NewImage1& 'sets alpha level of all colors to fade image page in/out _PUTIMAGE (0, 342), NewImage1& LOCATE 1, 1: PRINT "Alpha: "; a& _DISPLAY LOOP UNTIL a& = 0 END |
- Note: If the _CLEARCOLOR image background was not put onto a separate page, _SETALPHA would display it also.
See also
- _CLEARCOLOR (function)
- _SETALPHA (sets transparency level)
- _ALPHA, _ALPHA32 (read functions)
- Images, Creating Sprite Masks