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Active Forums => QB64 Discussion => Topic started by: thesolarcode on May 13, 2021, 03:53:00 pm

Title: Help: code not blending to complete black color
Post by: thesolarcode on May 13, 2021, 03:53:00 pm
I have this code and thought that with the _RGBA alpha setting (line 67) drawing over the whole screen the image should get darker and darker, but somehow the lines are stuck at some very dark grey color. Any idea how I can fix this?

Code: QB64: [Select]
  3.  
  4. dim shared screenx%, screeny%, tx1%, ty1%, tx2%, ty2%, x1%, y1%, x2%, y2%, d%
  5. screenx%=800
  6. screeny%=600
  7.        
  8. ' open new (full)screen
  9. SCREEN _NEWIMAGE(screenx%,screeny%,32)
  11.  
  12. tx1%=screenx%*rnd
  13. ty1%=screeny%*rnd
  14. tx2%=screenx%*rnd
  15. ty2%=screeny%*rnd
  16. x1%=screenx%*rnd
  17. y1%=screeny%*rnd
  18. x2%=screenx%*rnd
  19. y2%=screeny%*rnd
  20. d%=3
  21.  
  24.         color _RGB(256*rnd, 256*rnd, 256*rnd)
  25.         smearfx
  26.        
  27.         if x1% < tx1% then
  28.                 x1% = x1% + d%
  29.         ELSE
  30.                 x1% = x1% - d%
  31.         end if
  32.         if ABS(x1%-tx1%) < d% then
  33.                 tx1%=screenx%*rnd
  34.         end if
  35.  
  36.         if y1% < ty1% then
  37.                 y1% = y1% + d%
  38.         ELSE
  39.                 y1% = y1% - d%
  40.         end if
  41.         if abs(y1%-ty1%) < d% then
  42.                 ty1%=screeny%*rnd
  43.         end if
  44.        
  45.         if x2% < tx2% then
  46.                 x2% = x2% + d%
  47.         ELSE
  48.                 x2% = x2% - d%
  49.         end if
  50.         if abs(x2%-tx2%) < d% then
  51.                 tx2%=screenx%*rnd
  52.         end if
  53.  
  54.         if y2% < ty2% then
  55.                 y2% = y2% + d%
  56.         ELSE
  57.                 y2% = y2% - d%
  58.         end if
  59.         if abs(y2%-ty2%) < d% then
  60.                 ty2%=screeny%*rnd
  61.         end if
  64.  
  65. sub smearfx()
  66.     _LIMIT 50
  67.     LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 25), BF
  68.         line (x1%, y1%)-(x2%, y2%)
  69.     _DISPLAY
  71.  
Title: Re: Help: code not blending to complete black color
Post by: bplus on May 13, 2021, 04:36:43 pm
The screen is actually transparent until you cls, just cls will give default black background. That might help?

Hey nice effect!
Title: Re: Help: code not blending to complete black color
Post by: thesolarcode on May 13, 2021, 05:04:10 pm
Thanks,

Not sure how to use CLS without destroying the line effect - I only draw one additional line per screen update, all the other lines are just made darker with one command :)
I'm probably doing the wrong thing - am I effectively just setting transparency to 25% and thus lines are still visible?
Title: Re: Help: code not blending to complete black color
Post by: bplus on May 13, 2021, 05:08:41 pm
Oh just do it first thing before you start drawing, that sets the background to Black instead of transparent which looks black with no drawings on it.

I think you've got it right just CLS first thing, once, before drawing.
Title: Re: Help: code not blending to complete black color
Post by: FellippeHeitor on May 13, 2021, 05:38:39 pm
thesolarcode: I've tried to understand the effect you're seeing with programs I'd written before, like fireworks and others. I never managed to understand why it doesn't eventually end up blacking the whole screen - those trails will remain there until you actually clear the screen with full alpha. I managed to observe the same outcome while playing with other programming languages too, it's still a mystery to me.

Here, try this one: https://openprocessing.org/sketch/1191793 (same technique of semi-transparent black rectangle to cover previous frame - same trail effect (defect)).
Title: Re: Help: code not blending to complete black color
Post by: johnno56 on May 14, 2021, 03:41:27 am
I had a little problem when I ran this.... Cut and paste into IDE then F5. A small black window view appeared in the top left corner of the screen just for a moment. Pressed F5 again. The black window view appeared again and the whole display locked up. Rebooted. Re-ran. F5 black window again for a moment. F5 and the program ran normally. Escape to end. Tried again and the black window appeared again and locked up the system. Each time it locked up, the only two thing that worked was mouse movement and the system reset button....

I checked the listing. There doesn't seem to be anything there tat I have not used before (except for checking:off).

The time that it ran, it ran very well... I see what you mean about the 'dark grey' lines. Looks a lot like the qbasic screen saver, Mystify... Cool...

As the listing looks 'normal', I'm going to assume that the problem may be with my machine, and pass on running again until I try to figure out the problem.

I am running on Linux Mint 20, 64bit using QB64 1.5 stable from git 3043116
Title: Re: Help: code not blending to complete black color
Post by: johnno56 on May 14, 2021, 03:48:22 am
Ok. First test... Removal of 'checking:off'. Successfully ran the program 7 times in succession... Locked up on the 8th try.... Oh well.... Worth a shot...
Title: Re: Help: code not blending to complete black color
Post by: thesolarcode on May 14, 2021, 04:53:42 am
I changed the code a bit - this time I copy an image over and over to achieve the fading effect, but I have the same problem with the faded lines being still visible.
I guess there is no other way in QB64 as to darken/fade each pixel individually, right?

Code: QB64: [Select]
  2.  
  3. dim shared screenx%, screeny%, tx1%, ty1%, tx2%, ty2%, x1%, y1%, x2%, y2%, d%, handle2&
  4. screenx%=800
  5. screeny%=600
  6.        
  7. SCREEN _NEWIMAGE(screenx%,screeny%,32)
  10.  
  11. ' create new black image with alpha channel
  12. handle2& = _NEWIMAGE(screenx%,screeny%,32)
  13. _DEST handle2&
  14. LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 3), BF
  16.  
  17. tx1%=screenx%*rnd
  18. ty1%=screeny%*rnd
  19. tx2%=screenx%*rnd
  20. ty2%=screeny%*rnd
  21. x1%=screenx%*rnd
  22. y1%=screeny%*rnd
  23. x2%=screenx%*rnd
  24. y2%=screeny%*rnd
  25. d%=3
  26.  
  29.         color _RGB(256*rnd, 256*rnd, 256*rnd)
  30.         smearfx
  31.        
  32.         if x1% < tx1% then
  33.                 x1% = x1% + d%
  34.         ELSE
  35.                 x1% = x1% - d%
  36.         end if
  37.         if ABS(x1%-tx1%) < d% then
  38.                 tx1%=screenx%*rnd
  39.         end if
  40.  
  41.         if y1% < ty1% then
  42.                 y1% = y1% + d%
  43.         ELSE
  44.                 y1% = y1% - d%
  45.         end if
  46.         if abs(y1%-ty1%) < d% then
  47.                 ty1%=screeny%*rnd
  48.         end if
  49.        
  50.         if x2% < tx2% then
  51.                 x2% = x2% + d%
  52.         ELSE
  53.                 x2% = x2% - d%
  54.         end if
  55.         if abs(x2%-tx2%) < d% then
  56.                 tx2%=screenx%*rnd
  57.         end if
  58.  
  59.         if y2% < ty2% then
  60.                 y2% = y2% + d%
  61.         ELSE
  62.                 y2% = y2% - d%
  63.         end if
  64.         if abs(y2%-ty2%) < d% then
  65.                 ty2%=screeny%*rnd
  66.         end if
  69.  
  70. sub smearfx()
  71.     _LIMIT 50
  72.     'LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 25), BF
  73.     _PUTIMAGE (0,0), handle2&, 0
  74.     line (x1%, y1%)-(x2%, y2%)
  75.     _DISPLAY
  77.  
Title: Re: Help: code not blending to complete black color
Post by: johnno56 on May 14, 2021, 06:28:32 am
It's not just QB64. Because of my "screen lock" issue, I tried to replicate the problem, using RCBasic. No screen lockup but the "dark line" issue was still there. Reducing the "alpha" to "30" reduced it a little... Too low and the display looks like only a few lines or too high and the "grey line" is more obvious. I will continue to research...
Title: Re: Help: code not blending to complete black color
Post by: johnno56 on May 14, 2021, 09:17:28 am
Here is a rough conversion of a javascript example (
)

Even in the JS version, the remnants of the fading, was still present.

Code: QB64: [Select]
  1. DIM SHARED canvWidth
  2. DIM SHARED canvHeight
  3.  
  4. canvWidth = 800
  5. canvHeight = 600
  6. SCREEN _NEWIMAGE(canvWidth, canvHeight, 32)
  7.  
  10.  
  11. DIM SHARED x1, y1, x2, y2
  12. DIM SHARED xv1, yv1, xv2, yv2
  13.  
  14. DIM SHARED x1b, y1b, x2b, y2b
  15. DIM SHARED xv1b, yv1b, xv2b, yv2b
  16.  
  17. DIM SHARED alpha
  18.  
  19. cyan = _RGB32(0, 255, 255)
  20. yellow = _RGB32(255, 255, 0)
  21.  
  22. '   Init
  23. x1 = INT(RND * canvWidth)
  24. y1 = INT(RND * canvHeight)
  25. x2 = INT(RND * canvWidth)
  26. y2 = INT(RND * canvHeight)
  27.  
  28. x1b = INT(RND * canvWidth)
  29. y1b = INT(RND * canvHeight)
  30. x2b = INT(RND * canvWidth)
  31. y2b = INT(RND * canvHeight)
  32.  
  33. xv1 = 5 - INT(RND * 10)
  34. yv1 = 5 - INT(RND * 10)
  35. xv2 = 5 - INT(RND * 10)
  36. yv2 = 5 - INT(RND * 10)
  37.  
  38. xv1b = 5 - INT(RND * 10)
  39. yv1b = 5 - INT(RND * 10)
  40. xv2b = 5 - INT(RND * 10)
  41. yv2b = 5 - INT(RND * 10)
  42.  
  43. alpha = 30
  44.  
  46.     update
  48.  
  49. SUB update
  50.     _LIMIT 60
  51.     LINE (0, 0)-(canvWidth - 1, canvHeight - 1), _RGBA(0, 0, 64, alpha), BF
  52.     alpha = 15
  53.  
  54.     x1 = x1 + xv1
  55.     y1 = y1 + yv1
  56.     x2 = x2 + xv2
  57.     y2 = y2 + yv2
  58.     x1b = x1b + xv1b
  59.     y1b = y1b + yv1b
  60.     x2b = x2b + xv2b
  61.     y2b = y2b + yv2b
  62.  
  63.     IF x1 < 0 OR x1 > canvWidth THEN
  64.         xv1 = xv1 * -1
  65.     END IF
  66.     IF y1 < 0 OR y1 > canvHeight THEN
  67.         yv1 = yv1 * -1
  68.     END IF
  69.     IF x2 < 0 OR x2 > canvWidth THEN
  70.         xv2 = xv2 * -1
  71.     END IF
  72.     IF y2 < 0 OR y2 > canvHeight THEN
  73.         yv2 = yv2 * -1
  74.     END IF
  75.  
  76.     IF x1b < 0 OR x1b > canvWidth THEN
  77.         xv1b = xv1b * -1
  78.     END IF
  79.     IF y1b < 0 OR y1b > canvHeight THEN
  80.         yv1b = yv1b * -1
  81.     END IF
  82.     IF x2b < 0 OR x2b > canvWidth THEN
  83.         xv2b = xv2b * -1
  84.     END IF
  85.     IF y2b < 0 OR y2b > canvHeight THEN
  86.         yv2b = yv2b * -1
  87.     END IF
  88.  
  89.     LINE (x1, y1)-(x2, y2), _RGB32(0, 255, 255)
  90.     LINE (x1b, y1b)-(x2b, y2b), _RGB32(255, 255, 0)
  91.     _DISPLAY
  93.  
Title: Re: Help: code not blending to complete black color
Post by: NOVARSEG on May 15, 2021, 01:44:52 am
Quote
I guess there is no other way in QB64 as to darken/fade each pixel individually, right?

MEMGET and MEMPUT to the rescue


Code: QB64: [Select]
  2.  
  3. DIM SHARED screenx%, screeny%, tx1%, ty1%, tx2%, ty2%, x1%, y1%, x2%, y2%, d%, handle2&
  7.  
  10. DIM handle AS LONG
  11. screenx% = 800
  12. screeny% = 600
  13.  
  14. handle = _NEWIMAGE(screenx%, screeny%, 32)
  15.  
  16. m = _MEMIMAGE(handle)
  17.  
  18. SCREEN handle
  19.  
  21.  
  22. ' create new black image with alpha channel
  23. 'handle2& = _NEWIMAGE(screenx%, screeny%, 32)
  24. '_DEST handle2&
  25. 'LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 255), BF
  26. '_DEST 0
  27.  
  28. tx1% = screenx% * RND
  29. ty1% = screeny% * RND
  30. tx2% = screenx% * RND
  31. ty2% = screeny% * RND
  32. x1% = screenx% * RND
  33. y1% = screeny% * RND
  34. x2% = screenx% * RND
  35. y2% = screeny% * RND
  36. d% = 3
  37.  
  40.     COLOR _RGB(256 * RND, 256 * RND, 256 * RND)
  41.     ' smearfx
  42.  
  43.  
  44.     FOR T = 0 TO (800 * 600 - 1) * 4 STEP 4
  45.         B = _MEMGET(m, m.OFFSET + T, _UNSIGNED _BYTE)
  46.         G = _MEMGET(m, m.OFFSET + T + 1, _UNSIGNED _BYTE)
  47.         R = _MEMGET(m, m.OFFSET + T + 2, _UNSIGNED _BYTE)
  48.         IF B > 1 THEN B = B - 2
  49.         IF B = 1 THEN B = 0
  50.         IF G > 1 THEN G = G - 2
  51.         IF G = 1 THEN G = 0
  52.         IF R > 1 THEN R = R - 2
  53.         IF R = 1 THEN R = 0
  54.         _MEMPUT m, m.OFFSET + T, B
  55.         _MEMPUT m, m.OFFSET + T + 1, G
  56.         _MEMPUT m, m.OFFSET + T + 2, R
  57.     NEXT T
  58.  
  59.     IF x1% < tx1% THEN
  60.         x1% = x1% + d%
  61.     ELSE
  62.         x1% = x1% - d%
  63.     END IF
  64.     IF ABS(x1% - tx1%) < d% THEN
  65.         tx1% = screenx% * RND
  66.     END IF
  67.  
  68.     IF y1% < ty1% THEN
  69.         y1% = y1% + d%
  70.     ELSE
  71.         y1% = y1% - d%
  72.     END IF
  73.     IF ABS(y1% - ty1%) < d% THEN
  74.         ty1% = screeny% * RND
  75.     END IF
  76.  
  77.     IF x2% < tx2% THEN
  78.         x2% = x2% + d%
  79.     ELSE
  80.         x2% = x2% - d%
  81.     END IF
  82.     IF ABS(x2% - tx2%) < d% THEN
  83.         tx2% = screenx% * RND
  84.     END IF
  85.  
  86.     IF y2% < ty2% THEN
  87.         y2% = y2% + d%
  88.     ELSE
  89.         y2% = y2% - d%
  90.     END IF
  91.     IF ABS(y2% - ty2%) < d% THEN
  92.         ty2% = screeny% * RND
  93.     END IF
  94.  
  95.     LINE (x1%, y1%)-(x2%, y2%)
  97.  
  100. SUB smearfx ()
  101.     _LIMIT 50
  102.     LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 10), BF
  103.     '_PUTIMAGE (0, 0), handle2&, 0
  104.     LINE (x1%, y1%)-(x2%, y2%)
  105.     _DISPLAY

Title: Re: Help: code not blending to complete black color
Post by: thesolarcode on May 15, 2021, 02:32:34 am
Yes, that is it - the effect looks really great now (even better if you decrease by 1 - then it fades really slowly towards black color).
Today I learned something new (how to use MEMGET/PUT for gfx).
Thanks :)
Title: Re: Help: code not blending to complete black color
Post by: NOVARSEG on May 15, 2021, 03:09:54 am
Decrease by 1 does look better.

Title: Re: Help: code not blending to complete black color
Post by: NOVARSEG on May 15, 2021, 03:51:29 am
small bug . changed
 FOR T = 0 TO (800 * 600 - 1) * 4 STEP 4
to
FOR T = 0 TO 800 * 600 * 4 - 1 STEP 4


Code: QB64: [Select]
  2.  
  3. DIM SHARED screenx%, screeny%, tx1%, ty1%, tx2%, ty2%, x1%, y1%, x2%, y2%, d%, handle2&
  7.  
  10. DIM handle AS LONG
  11. screenx% = 800
  12. screeny% = 600
  13.  
  14. handle = _NEWIMAGE(screenx%, screeny%, 32)
  15.  
  16. m = _MEMIMAGE(handle)
  17.  
  18. SCREEN handle
  19.  
  21.  
  22. ' create new black image with alpha channel
  23. 'handle2& = _NEWIMAGE(screenx%, screeny%, 32)
  24. '_DEST handle2&
  25. 'LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 255), BF
  26. '_DEST 0
  27.  
  28. tx1% = screenx% * RND
  29. ty1% = screeny% * RND
  30. tx2% = screenx% * RND
  31. ty2% = screeny% * RND
  32. x1% = screenx% * RND
  33. y1% = screeny% * RND
  34. x2% = screenx% * RND
  35. y2% = screeny% * RND
  36. d% = 3
  37.  
  40.     COLOR _RGB(256 * RND, 256 * RND, 256 * RND)
  41.     ' smearfx
  42.  
  43.     FOR T = 0 TO 800 * 600 * 4 - 1 STEP 4
  44.         B = _MEMGET(m, m.OFFSET + T, _UNSIGNED _BYTE)
  45.         G = _MEMGET(m, m.OFFSET + T + 1, _UNSIGNED _BYTE)
  46.         R = _MEMGET(m, m.OFFSET + T + 2, _UNSIGNED _BYTE)
  47.         IF B > 1 THEN B = B - 1
  48.         'IF B = 1 THEN B = 0
  49.         IF G > 1 THEN G = G - 1
  50.         ' IF G = 1 THEN G = 0
  51.         IF R > 1 THEN R = R - 1
  52.         'IF R = 1 THEN R = 0
  53.         _MEMPUT m, m.OFFSET + T, B
  54.         _MEMPUT m, m.OFFSET + T + 1, G
  55.         _MEMPUT m, m.OFFSET + T + 2, R
  56.     NEXT T
  57.  
  58.     IF x1% < tx1% THEN
  59.         x1% = x1% + d%
  60.     ELSE
  61.         x1% = x1% - d%
  62.     END IF
  63.     IF ABS(x1% - tx1%) < d% THEN
  64.         tx1% = screenx% * RND
  65.     END IF
  66.  
  67.     IF y1% < ty1% THEN
  68.         y1% = y1% + d%
  69.     ELSE
  70.         y1% = y1% - d%
  71.     END IF
  72.     IF ABS(y1% - ty1%) < d% THEN
  73.         ty1% = screeny% * RND
  74.     END IF
  75.  
  76.     IF x2% < tx2% THEN
  77.         x2% = x2% + d%
  78.     ELSE
  79.         x2% = x2% - d%
  80.     END IF
  81.     IF ABS(x2% - tx2%) < d% THEN
  82.         tx2% = screenx% * RND
  83.     END IF
  84.  
  85.     IF y2% < ty2% THEN
  86.         y2% = y2% + d%
  87.     ELSE
  88.         y2% = y2% - d%
  89.     END IF
  90.     IF ABS(y2% - ty2%) < d% THEN
  91.         ty2% = screeny% * RND
  92.     END IF
  93.  
  94.     LINE (x1%, y1%)-(x2%, y2%)
  96.  
  99. SUB smearfx ()
  100.     _LIMIT 50
  101.     LINE (0, 0)-(screenx%, screeny%), _RGBA(0, 0, 0, 1), BF
  102.     _PUTIMAGE (0, 0), handle2&, 0
  103.     LINE (x1%, y1%)-(x2%, y2%)
  104.     _DISPLAY
  106.  
Title: Re: Help: code not blending to complete black color
Post by: johnno56 on May 15, 2021, 07:16:33 am
I still have difficulty executing. Eventually it started and the fade effect is much better... Well done!
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