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Active Forums => QB64 Discussion => Topic started by: bplus on October 04, 2021, 10:16:51 am

Title: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 10:16:51 am
This question came up last night with Dav's Pipe Connecting Puzzle:

Is there a way to fade an image in or out without having to resort to a pixel at a time with Point?

That would be so nice to use for ghostly faces and other Halloween tricks.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: SMcNeill on October 04, 2021, 10:24:59 am
Cover it with an alpha colored box.

Image is from (100,100)-(200,200)

FOR I = 1 TO 10
   LINE(100,100)-(200,200), _RGBA(0, 0, 0, 100), BF
NEXT

Will fade to black over multiple passes.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: SMcNeill on October 04, 2021, 10:30:27 am
Or pre-alpha your image to various levels and save an array of them.  Then you can pick and choose which one you need for the current stage of the effect.

FOR I = 1 TO 10
    CLS, RED
    PUTIMAGE (x, y), faded_image(i)
    SLEEP
NEXT

^fresh red background with you putting 10 different alpha backgrounds over it one at a time.

Which might also be accomplished via SETALPHA.

https://www.qb64.org/wiki/SETALPHA
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: Cobalt on October 04, 2021, 12:37:47 pm
There is a routine in the wiki to do just that.... give me a second...

cant quite remember where it is in the wiki but here is the copy I've been using(how things fade in Dragon Warrior)

Code: QB64: [Select]
  1. SUB Fade_Out (L&)
  2.  FOR n! = 1 TO 0.00 STEP -0.05
  3.   i2& = _COPYIMAGE(L&)
  4.   DarkenImage i2&, n!
  5.   _PUTIMAGE (0, 0), i2&, Layer(0)
  6.   _FREEIMAGE i2&
  7.   _DELAY .06
  10.  
  11. SUB Fade_In (L&)
  12.  FOR n! = 0.01 TO 1 STEP 0.05
  13.   i2& = _COPYIMAGE(L&)
  14.   DarkenImage i2&, n!
  15.   _PUTIMAGE (0, 0), i2&, Layer(0)
  16.   _FREEIMAGE i2&
  17.   _DELAY .06
  20.  
  21. SUB DarkenImage (Image AS LONG, Value_From_0_To_1 AS SINGLE)
  22.  IF Value_From_0_To_1 <= 0 OR Value_From_0_To_1 >= 1 OR _PIXELSIZE(Image) <> 4 THEN EXIT SUB
  23.  DIM Buffer AS _MEM: Buffer = _MEMIMAGE(Image) 'Get a memory reference to our image
  24.  DIM Frac_Value AS LONG: Frac_Value = Value_From_0_To_1 * 65536 'Used to avoid slow floating point calculations
  25.  DIM O AS _OFFSET, O_Last AS _OFFSET
  26.  O = Buffer.OFFSET 'We start at this offset
  27.  O_Last = Buffer.OFFSET + _WIDTH(Image) * _HEIGHT(Image) * 4 'We stop when we get to this offset
  28.  'use on error free code ONLY!
  30.  DO
  31.   _MEMPUT Buffer, O, _MEMGET(Buffer, O, _UNSIGNED _BYTE) * Frac_Value \ 65536 AS _UNSIGNED _BYTE
  32.   _MEMPUT Buffer, O + 1, _MEMGET(Buffer, O + 1, _UNSIGNED _BYTE) * Frac_Value \ 65536 AS _UNSIGNED _BYTE
  33.   _MEMPUT Buffer, O + 2, _MEMGET(Buffer, O + 2, _UNSIGNED _BYTE) * Frac_Value \ 65536 AS _UNSIGNED _BYTE
  34.   O = O + 4
  35.  LOOP UNTIL O = O_Last
  36.  'turn checking back on when done!
  38.  _MEMFREE Buffer
  40.  
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 12:43:06 pm
Thanks again Steve, _SetAlpha is probably the tool I had in mind.

I think I meant to say I wanted a transparent image laid over an background and gradually change from transparent to opaque.

Actually I started to consider random filling another image over a background image with Point at a low to middle transparency.

Oh Cobalt has posted, I will read next.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 12:45:52 pm
@Colbalt very interesting, thank you.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: Cobalt on October 04, 2021, 04:09:47 pm
Your Welcome.
I've found it to be useful.
Layer(0) is basically _DISPLAY
Adjusting the _DELAY can make it fade slower or faster was well as the STEP in the FOR.
And of course you don't have to fade all the way in or out, you can have it stop where ever, but I've only ever used it for full in and outs.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: Pete on October 04, 2021, 04:37:47 pm
Didn't we go over this in my Ghost Town game thread?

Code: QB64: [Select]
  1. SCREEN _NEWIMAGE(600, 600, 32)
  2.  
  3. img& = _LOADIMAGE("C:\QB64\YS.png")
  4.  
  6.     FOR i = 0 TO 255
  7.         CLS
  8.         addAlpha2Img img&, -1 'subtract 1 alpha value from each pixel.
  9.         _PUTIMAGE (0, 0)-(600, 600), img&
  10.         _LIMIT 40
  11.         _DISPLAY
  12.     NEXT
  13.  
  14.     FOR i = 255 TO 0 STEP -1
  15.         addAlpha2Img img&, 1 'subtract 1 alpha value from each pixel.
  16.         _PUTIMAGE (0, 0)-(600, 600), img&
  17.         _LIMIT 40
  18.         _DISPLAY
  19.         CLS
  20.     NEXT
  22.  
  23. SUB addAlpha2Img (img&, alpha AS INTEGER)
  24.     IF img& >= -1 THEN EXIT SUB
  25.     DIM buffer AS _MEM, o AS _OFFSET, o2 AS _OFFSET
  28.     buffer = _MEMIMAGE(img&)
  29.     o = buffer.OFFSET
  30.     o2 = o + _WIDTH(img&) * _HEIGHT(img&) * 4
  31.     DO
  32.         b = _MEMGET(buffer, o + 3, _UNSIGNED _BYTE)
  33.         IF (b + alpha) > 0 AND (b + alpha) < 255 THEN
  34.             _MEMPUT buffer, o + 3, (b + alpha) AS _UNSIGNED _BYTE
  35.         END IF
  36.         o = o + 4
  37.     LOOP UNTIL o = o2
  38.     _MEMFREE buffer
  41.  

To run code, download my Yosemite Sam avatar to the QB64 folder and rename it as YS.png.

Credit to Ashish, who I believe created this effect a few years back. My apologies to whomever did create it, if I got that wrong.

Pete
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 05:17:45 pm
Yeah that was Ashish but I had something more ghostly:
https://www.qb64.org/forum/index.php?topic=4118.msg134736#msg134736
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 05:19:22 pm
@Pete That wasn't a Fade In / Out that was only blocking out the background image.
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: Pete on October 04, 2021, 05:23:56 pm
Sam with a pair of phasers, maybe. Sam with a pair of light sabres, never!

Pete
Title: Re: Looking for Way to Fade In (or Out) an Image
Post by: bplus on October 04, 2021, 05:26:56 pm
Quote from: Pete on October 04, 2021, 05:23:56 pm
Sam with a pair of phasers, maybe. Sam with a pair of light sabres, never!

Pete

Like say, over your dead body! :)
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