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Active Forums => Programs => Topic started by: bplus on June 21, 2019, 12:49:32 pm

Title: Color Dialog
Post by: bplus on June 21, 2019, 12:49:32 pm
OK what did I forget?
Code: QB64: [Select]
  2. _TITLE "Color Dialog" 'started by B+ 2019-06-21
  3.  
  4. 'from :"Color CONST for _RGBA32(red, green, blue, alpha)" 'B+ 2019-05-19
  5. '2019-05-26 update this for mouse inputs
  6. '>>>>>>>>>>>> test your colors here
  7. '>>>>>>>>>>>> then create and name Hex string CONSTs if you want to the Clipboard
  8. 'sample clipping
  9. CONST Purple = &HFFB400B4
  10. ' 2019-06-21 start color dialog
  11.  
  12. SCREEN _NEWIMAGE(1200, 700, 32)
  13. _SCREENMOVE 100, 20
  15. COLOR &HFF0000BB, &HFFAAAAAA
  16. FOR i = 1 TO 150
  17.     LINE (RND * 1200, RND * 700)-STEP(RND * 50, RND * 50), _RGB32(RND * 255, RND * 255, RND * 255), BF
  19. PRINT "in 4 secs Color Dialog comes up..."
  22. colorDialog rc
  23. PRINT "Color Dialog returned this:"; rc
  24. IF rc <> 0 THEN LINE (100, 100)-STEP(1000, 500), rc, BF
  25. PRINT: PRINT "End of Color Dialog test..."
  26.  
  27. SUB colorDialog (returnColor AS _UNSIGNED LONG)
  28.  
  29.     'first screen dimensions items to restore at exit
  30.     DIM curRow AS INTEGER, curCol AS INTEGER, autoDisplay AS INTEGER
  32.     DIM curScrn AS LONG, backScrn AS LONG 'some handles
  33.  
  34.     DIM cd AS LONG
  36.     DIM makeConst$, k$
  37.  
  38.     'save old settings to restore at end ofsub
  39.     curRow = CSRLIN
  40.     curCol = POS(0)
  41.     autoDisplay = _AUTODISPLAY
  42.     sw = _WIDTH
  43.     sh = _HEIGHT
  44.     fg = _DEFAULTCOLOR
  45.     bg = _BACKGROUNDCOLOR
  46.     _KEYCLEAR
  47.     'screen snapshot
  48.     curScrn = _DEST
  49.     backScrn = _NEWIMAGE(sw, sh, 32)
  50.     _PUTIMAGE , curScrn, backScrn
  51.  
  52.     cd = _NEWIMAGE(800, 600, 32)
  53.     SCREEN cd
  54.     r = 128: g = 128: b = 128: a = 128
  55.     COLOR &HFFDDDDDD, 0
  56.     DO
  57.         CLS
  58.         makeConst$ = "&H" + RIGHT$(STRING$(8, "0") + HEX$(_RGBA32(r, g, b, a)), 8)
  59.         slider 16, 10, r, "Red"
  60.         slider 16, 60, g, "Green"
  61.         slider 16, 110, b, "Blue"
  62.         slider 16, 160, a, "Alpha"
  63.         _PRINTSTRING (150, 260), "Press enter or spacenbar, if you want to use the color: " + makeConst$
  64.         _PRINTSTRING (210, 280), "Press escape or q, to not use any color, returns 0."
  65.         LINE (90, 300)-(710, 590), , B
  66.         LINE (100, 310)-(700, 580), VAL(makeConst$), BF
  67.  
  68.         WHILE _MOUSEINPUT: WEND
  69.         mb = _MOUSEBUTTON(1)
  70.         IF mb THEN 'clear it
  71.             mx = _MOUSEX: my = _MOUSEY
  72.             IF mx >= 16 AND mx <= 784 THEN
  73.                 IF my >= 10 AND my <= 50 THEN
  74.                     r = _ROUND((mx - 16) / 3)
  75.                 ELSEIF my >= 60 AND my <= 100 THEN
  76.                     g = _ROUND((mx - 16) / 3)
  77.                 ELSEIF my >= 110 AND my <= 150 THEN
  78.                     b = _ROUND((mx - 16) / 3)
  79.                 ELSEIF my >= 160 AND my <= 200 THEN
  80.                     a = _ROUND((mx - 16) / 3)
  81.                 END IF
  82.             END IF
  83.         END IF
  84.         k$ = INKEY$
  85.         IF LEN(k$) THEN
  86.             IF ASC(k$) = 27 OR k$ = "q" THEN returnColor = 0: EXIT DO
  87.             IF ASC(k$) = 13 OR k$ = " " THEN returnColor = _RGBA32(r, g, b, a): EXIT DO
  88.         END IF
  89.         _DISPLAY
  90.         _LIMIT 60
  91.     LOOP
  92.  
  93.     'put things back
  94.     SCREEN curScrn
  95.     COLOR _RGB32(255, 255, 255), _RGB32(0, 0, 0): CLS
  96.     _PUTIMAGE , backScrn
  97.     _DISPLAY
  98.     COLOR fg, bg
  99.     _FREEIMAGE backScrn
  100.     _FREEIMAGE cd
  101.     IF autoDisplay THEN _AUTODISPLAY
  102.     'clear key presses
  103.     _KEYCLEAR
  104.     'clear mouse clicks
  106.     mb = _MOUSEBUTTON(1)
  107.     IF mb THEN 'clear it
  108.         WHILE mb 'OK!
  109.             IF _MOUSEINPUT THEN mb = _MOUSEBUTTON(1)
  110.             _LIMIT 10
  111.         WEND
  112.     END IF
  113.     LOCATE curRow, curCol
  114.  
  116.  
  117. SUB slider (x, y, value, label$)
  118.     DIM c~&, s$
  119.     SELECT CASE label$
  120.         CASE "Red": c~& = &HFFFF0000
  121.         CASE "Green": c~& = &HFF008800
  122.         CASE "Blue": c~& = &HFF0000FF
  123.         CASE "Alpha": c~& = &H88FFFFFF
  124.     END SELECT
  125.     LINE (x, y)-STEP(768, 40), c~&, B
  126.     LINE (x, y)-STEP(3 * value, 40), c~&, BF
  127.     s$ = label$ + " = " + _TRIM$(STR$(value))
  128.     _PRINTSTRING (x + 384 - 4 * LEN(s$), y + 12), s$
  130.  
Title: Re: Color Dialog
Post by: Petr on June 21, 2019, 01:21:53 pm
Hi BPlus, do you remember that Alpha changes color depending on the background color? This means that the resulting color will always be of a different appearance but of the same value if you add a different screen clearing color than black to the CLS command on row 57?

This assumes that you apply the obtained value as a color number to different commands. Then there will be color mixing (for alpha < 255) depending on the background. The only way in which background color mixing does not occur is to insert colors into the image directly with the MEM command.
Title: Re: Color Dialog
Post by: Dimster on June 21, 2019, 01:34:58 pm
What a handy little Color Mix Decoder for want of something more descriptive. I don't exactly follow what Petr is pointing out. I do see where, if I set the Alpha to zero there is no color whatever the RBG settings, and with Alpha at it's highest level, color mixes seem more vibrant. I normally work with adding color on a black background, is Petr saying the color mix this program provides ONLY works on a black background?

Thanks bplus - was handy hexidecimeter.
Title: Re: Color Dialog
Post by: Petr on June 21, 2019, 01:52:16 pm
Here I solved it. Fellippe explained it to me. https://www.qb64.org/forum/index.php?topic=1325.0
Title: Re: Color Dialog
Post by: bplus on June 21, 2019, 02:10:38 pm
Hi,

I think what Petr is concerned about is that if I lay a transparent color over another color and then take a POINT reading of that color value, the POINT will return Neither the transparent color value Nor the original color value that it overlaid. POINT will return some blend of those two numbers.

Petr's point gives me the idea to show a range of colors for background, so that one can see how the transparent or even the solid colors being tested compare to other colors side by side.

Correct me please if I am wrong.
Title: Re: Color Dialog
Post by: bplus on June 21, 2019, 02:17:46 pm
Oh, also which would be better to return: the Hexidecimal$ which a FUNCTION can return or the _UNSIGNED LONG value that _RGBA() function gives us which, I think, we can't return with FUNCTIONs (hence my use of a SUB)?
Title: Re: Color Dialog
Post by: Petr on June 21, 2019, 02:30:50 pm
I don't understand exactly your question. Both the SUB and the FUNCTION can return an unsigned long value. Just use ~& in function name, something as FUNCTION GETCOLOR~& to return these values, for SUB, follow these steps:

DIM c AS _UNSIGNED LONG
GetColor c~&
PRINT _ALPHA32(c~&), _RED32(c~&), _GREEN32(c~&), _BLUE32(c~&)


SUB GetColor (OutColor AS _UNSIGNED LONG)
    OutColor~& = &HFFFF0000
END SUB

Quote
Petr's point gives me the idea to show a range of colors for background, so that one can see how the transparent or even the solid colors being tested compare to other colors side by side.

I am curious to the way you want to do it. Perhaps it would be if the user set a background color where he apply a new color... but how do you do this in case, for example, a partially transparent rectangle will paint over many different colors?

Title: Re: Color Dialog
Post by: bplus on June 21, 2019, 03:12:54 pm
Quote
Both the SUB and the FUNCTION can return an unsigned long value. Just use ~& in function name, something as FUNCTION GETCOLOR~& to return these values, for SUB, follow these steps:

Right, there was some reason I did not like or did not want ~& at the end of a function name...

Here is mod that returns the Hex$ and shows what the color looks like laid over a host of color!
To use the hex$ value just apply VAL(hex$):
Code: QB64: [Select]
  2. _TITLE "Color Dialog" 'started by B+ 2019-06-21
  3.  
  4. 'from :"Color CONST for _RGBA32(red, green, blue, alpha)" 'B+ 2019-05-19
  5. '2019-05-26 update this for mouse inputs
  6. '>>>>>>>>>>>> test your colors here
  7. '>>>>>>>>>>>> then create and name Hex string CONSTs if you want to the Clipboard
  8. 'sample clipping
  9. CONST Purple = &HFFB400B4
  10. ' 2019-06-21 start Color Dialog
  11.  
  12. SCREEN _NEWIMAGE(1200, 700, 32)
  13. _SCREENMOVE 100, 20
  14. DIM rc$, i
  15. COLOR &HFF0000BB, &HFFAAAAAA
  16. FOR i = 1 TO 150
  17.     LINE (RND * 1200, RND * 700)-STEP(RND * 150, RND * 150), _RGBA32(RND * 256, RND * 256, RND * 256, RND * 256), BF
  19. PRINT "in 4 secs Color Dialog comes up..."
  22. rc$ = colorDialog$
  23. PRINT "Color Dialog returned this:"; rc$
  24. IF rc$ <> "" THEN LINE (100, 100)-STEP(1000, 500), VAL(rc$), BF
  25. PRINT: PRINT "End of Color Dialog test..."
  26.  
  27. FUNCTION colorDialog$
  28.  
  29.     'first screen dimensions items to restore at exit
  30.     DIM curRow AS INTEGER, curCol AS INTEGER, autoDisplay AS INTEGER
  32.     DIM curScrn AS LONG, backScrn AS LONG 'some handles
  33.  
  34.     DIM cd AS LONG
  36.     DIM makeConst$, k$
  37.     DIM f AS SINGLE
  38.  
  39.     'save old settings to restore at end ofsub
  40.     curRow = CSRLIN
  41.     curCol = POS(0)
  42.     autoDisplay = _AUTODISPLAY
  43.     sw = _WIDTH
  44.     sh = _HEIGHT
  45.     fg = _DEFAULTCOLOR
  46.     bg = _BACKGROUNDCOLOR
  47.     _KEYCLEAR
  48.     'screen snapshot
  49.     curScrn = _DEST
  50.     backScrn = _NEWIMAGE(sw, sh, 32)
  51.     _PUTIMAGE , curScrn, backScrn
  52.  
  53.     cd = _NEWIMAGE(800, 600, 32)
  54.     SCREEN cd
  55.     r = 128: g = 128: b = 128: a = 128
  56.     COLOR &HFFDDDDDD, 0
  57.     DO
  58.         CLS
  59.         makeConst$ = "&H" + RIGHT$(STRING$(8, "0") + HEX$(_RGBA32(r, g, b, a)), 8)
  60.         slider 16, 10, r, "Red"
  61.         slider 16, 60, g, "Green"
  62.         slider 16, 110, b, "Blue"
  63.         slider 16, 160, a, "Alpha"
  64.         _PRINTSTRING (150, 260), "Press enter or spacenbar, if you want to use the color: " + makeConst$
  65.         _PRINTSTRING (210, 280), "Press escape or q, to not use any color, returns 0."
  66.         LINE (90, 300)-(710, 590), , B
  67.         FOR i = 100 TO 700
  68.             f = 255 * (i - 100) / 600
  69.             LINE (i, 310)-STEP(0, 30), _RGB32(f, 0, 0)
  70.             LINE (i, 340)-STEP(0, 30), _RGB32(0, f, 0)
  71.             LINE (i, 370)-STEP(0, 30), _RGB32(0, 0, f)
  72.             LINE (i, 400)-STEP(0, 30), _RGB32(f, f, 0)
  73.             LINE (i, 430)-STEP(0, 30), _RGB32(0, f, f)
  74.             LINE (i, 460)-STEP(0, 30), _RGB32(f, 0, f)
  75.             LINE (i, 490)-STEP(0, 30), _RGB32(f, f, f)
  76.             LINE (i, 520)-STEP(0, 30), _RGB32(0, 0, 0)
  77.             LINE (i, 550)-STEP(0, 30), _RGB32(255, 255, 255)
  78.         NEXT
  79.         LINE (100, 310)-(700, 580), VAL(makeConst$), BF
  80.         WHILE _MOUSEINPUT: WEND
  81.         mb = _MOUSEBUTTON(1)
  82.         IF mb THEN 'clear it
  83.             mx = _MOUSEX: my = _MOUSEY
  84.             IF mx >= 16 AND mx <= 781 THEN
  85.                 IF my >= 10 AND my <= 50 THEN
  86.                     r = INT((mx - 16) / 3)
  87.                 ELSEIF my >= 60 AND my <= 100 THEN
  88.                     g = INT((mx - 16) / 3)
  89.                 ELSEIF my >= 110 AND my <= 150 THEN
  90.                     b = INT((mx - 16) / 3)
  91.                 ELSEIF my >= 160 AND my <= 200 THEN
  92.                     a = INT((mx - 16) / 3)
  93.                 END IF
  94.             END IF
  95.         END IF
  96.         k$ = INKEY$
  97.         IF LEN(k$) THEN
  98.             IF ASC(k$) = 27 OR k$ = "q" THEN EXIT DO
  99.             IF ASC(k$) = 13 OR k$ = " " THEN colorDialog$ = makeConst$: EXIT DO
  100.         END IF
  101.         _DISPLAY
  102.         _LIMIT 60
  103.     LOOP
  104.  
  105.     'put things back
  106.     SCREEN curScrn
  107.     COLOR _RGB32(255, 255, 255), _RGB32(0, 0, 0): CLS
  108.     _PUTIMAGE , backScrn
  109.     _DISPLAY
  110.     COLOR fg, bg
  111.     _FREEIMAGE backScrn
  112.     _FREEIMAGE cd
  113.     IF autoDisplay THEN _AUTODISPLAY
  114.     'clear key presses
  115.     _KEYCLEAR
  116.     'clear mouse clicks
  118.     mb = _MOUSEBUTTON(1)
  119.     IF mb THEN 'clear it
  120.         WHILE mb 'OK!
  121.             IF _MOUSEINPUT THEN mb = _MOUSEBUTTON(1)
  122.             _LIMIT 10
  123.         WEND
  124.     END IF
  125.     LOCATE curRow, curCol
  126.  
  128.  
  129. SUB slider (x, y, value, label$)
  130.     DIM c~&, s$
  131.     SELECT CASE label$
  132.         CASE "Red": c~& = &HFFFF0000
  133.         CASE "Green": c~& = &HFF008800
  134.         CASE "Blue": c~& = &HFF0000FF
  135.         CASE "Alpha": c~& = &H88FFFFFF
  136.     END SELECT
  137.     LINE (x, y)-STEP(765, 40), c~&, B
  138.     LINE (x, y)-STEP(3 * value, 40), c~&, BF
  139.     s$ = label$ + " = " + _TRIM$(STR$(value))
  140.     _PRINTSTRING (x + 384 - 4 * LEN(s$), y + 12), s$
  142.  

 


Well the solid colors will just be one solid block... :)
Oh wait... got another idea :)
Title: Re: Color Dialog
Post by: bplus on June 21, 2019, 03:37:12 pm
Side by side and overlay:
Code: QB64: [Select]
  2. _TITLE "Color Dialog" 'started by B+ 2019-06-21
  3.  
  4. 'from :"Color CONST for _RGBA32(red, green, blue, alpha)" 'B+ 2019-05-19
  5. '2019-05-26 update this for mouse inputs
  6. '>>>>>>>>>>>> test your colors here
  7. '>>>>>>>>>>>> then create and name Hex string CONSTs if you want to the Clipboard
  8. 'sample clipping
  9. CONST Purple = &HFFB400B4
  10. ' 2019-06-21 start Color Dialog
  11.  
  12. SCREEN _NEWIMAGE(1200, 700, 32)
  13. _SCREENMOVE 100, 20
  14. DIM rc$, i
  15. COLOR &HFF0000BB, &HFFAAAAAA
  16. FOR i = 1 TO 150
  17.     LINE (RND * 1200, RND * 700)-STEP(RND * 150, RND * 150), _RGBA32(RND * 256, RND * 256, RND * 256, RND * 256), BF
  19. PRINT "in 4 secs Color Dialog comes up..."
  22. rc$ = colorDialog$
  23. PRINT "Color Dialog returned this:"; rc$
  24. IF rc$ <> "" THEN LINE (100, 100)-STEP(1000, 500), VAL(rc$), BF
  25. PRINT: PRINT "End of Color Dialog test..."
  26.  
  27. FUNCTION colorDialog$
  28.  
  29.     'first screen dimensions items to restore at exit
  30.     DIM curRow AS INTEGER, curCol AS INTEGER, autoDisplay AS INTEGER
  32.     DIM curScrn AS LONG, backScrn AS LONG 'some handles
  33.  
  34.     DIM cd AS LONG
  36.     DIM makeConst$, k$
  37.     DIM f AS SINGLE
  38.  
  39.     'save old settings to restore at end ofsub
  40.     curRow = CSRLIN
  41.     curCol = POS(0)
  42.     autoDisplay = _AUTODISPLAY
  43.     sw = _WIDTH
  44.     sh = _HEIGHT
  45.     fg = _DEFAULTCOLOR
  46.     bg = _BACKGROUNDCOLOR
  47.     _KEYCLEAR
  48.     'screen snapshot
  49.     curScrn = _DEST
  50.     backScrn = _NEWIMAGE(sw, sh, 32)
  51.     _PUTIMAGE , curScrn, backScrn
  52.  
  53.     cd = _NEWIMAGE(800, 600, 32)
  54.     SCREEN cd
  55.     r = 128: g = 128: b = 128: a = 128
  56.     COLOR &HFFDDDDDD, 0
  57.     DO
  58.         CLS
  59.         makeConst$ = "&H" + RIGHT$(STRING$(8, "0") + HEX$(_RGBA32(r, g, b, a)), 8)
  60.         slider 16, 10, r, "Red"
  61.         slider 16, 60, g, "Green"
  62.         slider 16, 110, b, "Blue"
  63.         slider 16, 160, a, "Alpha"
  64.         _PRINTSTRING (150, 260), "Press enter or spacenbar, if you want to use the color: " + makeConst$
  65.         _PRINTSTRING (210, 280), "Press escape or q, to not use any color, returns 0."
  66.         LINE (90, 300)-(710, 590), , B
  67.         FOR i = 100 TO 700
  68.             f = 255 * (i - 100) / 600
  69.             LINE (i, 310)-STEP(0, 30), _RGB32(f, 0, 0): LINE (i, 310)-STEP(0, 20), VAL(makeConst$)
  70.             LINE (i, 340)-STEP(0, 30), _RGB32(0, f, 0): LINE (i, 340)-STEP(0, 20), VAL(makeConst$)
  71.             LINE (i, 370)-STEP(0, 30), _RGB32(0, 0, f): LINE (i, 370)-STEP(0, 20), VAL(makeConst$)
  72.             LINE (i, 400)-STEP(0, 30), _RGB32(f, f, 0): LINE (i, 400)-STEP(0, 20), VAL(makeConst$)
  73.             LINE (i, 430)-STEP(0, 30), _RGB32(0, f, f): LINE (i, 430)-STEP(0, 20), VAL(makeConst$)
  74.             LINE (i, 460)-STEP(0, 30), _RGB32(f, 0, f): LINE (i, 460)-STEP(0, 20), VAL(makeConst$)
  75.             LINE (i, 490)-STEP(0, 30), _RGB32(f, f, f): LINE (i, 490)-STEP(0, 20), VAL(makeConst$)
  76.             LINE (i, 520)-STEP(0, 30), _RGB32(0, 0, 0): LINE (i, 520)-STEP(0, 20), VAL(makeConst$)
  77.             LINE (i, 550)-STEP(0, 30), _RGB32(255, 255, 255): LINE (i, 550)-STEP(0, 20), VAL(makeConst$)
  78.         NEXT
  79.         WHILE _MOUSEINPUT: WEND
  80.         mb = _MOUSEBUTTON(1)
  81.         IF mb THEN 'clear it
  82.             mx = _MOUSEX: my = _MOUSEY
  83.             IF mx >= 16 AND mx <= 781 THEN
  84.                 IF my >= 10 AND my <= 50 THEN
  85.                     r = INT((mx - 16) / 3)
  86.                 ELSEIF my >= 60 AND my <= 100 THEN
  87.                     g = INT((mx - 16) / 3)
  88.                 ELSEIF my >= 110 AND my <= 150 THEN
  89.                     b = INT((mx - 16) / 3)
  90.                 ELSEIF my >= 160 AND my <= 200 THEN
  91.                     a = INT((mx - 16) / 3)
  92.                 END IF
  93.             END IF
  94.         END IF
  95.         k$ = INKEY$
  96.         IF LEN(k$) THEN
  97.             IF ASC(k$) = 27 OR k$ = "q" THEN EXIT DO
  98.             IF ASC(k$) = 13 OR k$ = " " THEN colorDialog$ = makeConst$: EXIT DO
  99.         END IF
  100.         _DISPLAY
  101.         _LIMIT 60
  102.     LOOP
  103.  
  104.     'put things back
  105.     SCREEN curScrn
  106.     COLOR _RGB32(255, 255, 255), _RGB32(0, 0, 0): CLS
  107.     _PUTIMAGE , backScrn
  108.     _DISPLAY
  109.     COLOR fg, bg
  110.     _FREEIMAGE backScrn
  111.     _FREEIMAGE cd
  112.     IF autoDisplay THEN _AUTODISPLAY
  113.     'clear key presses
  114.     _KEYCLEAR
  115.     'clear mouse clicks
  117.     mb = _MOUSEBUTTON(1)
  118.     IF mb THEN 'clear it
  119.         WHILE mb 'OK!
  120.             IF _MOUSEINPUT THEN mb = _MOUSEBUTTON(1)
  121.             _LIMIT 10
  122.         WEND
  123.     END IF
  124.     LOCATE curRow, curCol
  125.  
  127.  
  128. SUB slider (x, y, value, label$)
  129.     DIM c~&, s$
  130.     SELECT CASE label$
  131.         CASE "Red": c~& = &HFFFF0000
  132.         CASE "Green": c~& = &HFF008800
  133.         CASE "Blue": c~& = &HFF0000FF
  134.         CASE "Alpha": c~& = &H88FFFFFF
  135.     END SELECT
  136.     LINE (x, y)-STEP(765, 40), c~&, B
  137.     LINE (x, y)-STEP(3 * value, 40), c~&, BF
  138.     s$ = label$ + " = " + _TRIM$(STR$(value))
  139.     _PRINTSTRING (x + 384 - 4 * LEN(s$), y + 12), s$
  141.  

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Title: Re: Color Dialog
Post by: SMcNeill on June 21, 2019, 03:39:30 pm
Quote from: Petr on June 21, 2019, 01:21:53 pm
Hi BPlus, do you remember that Alpha changes color depending on the background color? This means that the resulting color will always be of a different appearance but of the same value if you add a different screen clearing color than black to the CLS command on row 57?

This assumes that you apply the obtained value as a color number to different commands. Then there will be color mixing (for alpha < 255) depending on the background. The only way in which background color mixing does not occur is to insert colors into the image directly with the MEM command.

Or set _DONTBLEND.

https://www.qb64.org/wiki/BLEND
https://www.qb64.org/wiki/DONTBLEND
Title: Re: Color Dialog
Post by: SMcNeill on June 21, 2019, 03:59:15 pm
A quick demo to highlight the difference of blended and unblended colors.:

Code: [Select]
SCREEN _NEWIMAGE(640, 480, 32)

CLS , &HFF000000~&
_BLEND
LINE (0, 0)-(640, 480), &H99FFFFFF~&, BF 'faded white background box
PRINT "Black color: "; HEX$(&HFF000000~&)
PRINT "Box color: "; HEX$(&H99FFFFFF~&)
PRINT "Mixed color: "; HEX$(POINT(300, 300))
PRINT "(These are values of blended colors.)"

SLEEP 'Pause for user input


CLS , &HFF000000~&
_DONTBLEND
LINE (0, 0)-(640, 480), &H99FFFFFF~&, BF 'faded white background box
PRINT "Black color: "; HEX$(&HFF000000~&)
PRINT "Box color: "; HEX$(&H99FFFFFF~&)
PRINT "Mixed color: "; HEX$(POINT(300, 300))
PRINT "(These are values of unblended colors.)"

If the color mixer is going to have alpha settings, you'll probably want to run your program in a _DONTBLEND state so that the background doesn't affect the true appearance of the chosen color.  (Or else add a toggle button to swap between Blend and Not Blend, so the user could see how the alpha value would end up actually looking in real conditions with their backgrounds.)
Title: Re: Color Dialog
Post by: Petr on June 21, 2019, 04:15:53 pm
Yes. If the user exactly specifies the area where the color will be applied, then the resulting color with the alpha channel application can be shown to the user and set. Without background knowledge, there is no way to determine how the color see, if the alpha channel will be less than 255.
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