Is there a faster way to do this glow circle effect?

[justsomeguy]

I created this a while back for a project. It uses a look up table of distances to set the intensity of the pixel, giving it a soft edge. With very little modification to the color mixing, you can create different colors of spot lights.

Code: (Select All)

'#######################################################

'#                Spolight Demo                      #

'#######################################################

_TITLE "Spotlight Demo"

CONST spotLightSize = 128



DIM AS DOUBLE distLUT(spotLightSize * 2, spotLightSize * 2)

DIM AS LONG scr, img, colour, iter

DIM AS STRING fl

DIM AS DOUBLE xp, yp, xl, yl

DIM AS DOUBLE dist, percentage



'#######################################################

'#          Setup Screen and load Image                #

'#######################################################

' main draw screen

scr = _NEWIMAGE(1000, 600, 32)

' hidden reference image

backscr = _NEWIMAGE(1000, 600, 32)

' Change this to whatever image you want to open.

fl = "cactus.jpg"

img = _LOADIMAGE(fl, 32)

' Draw it to the hidden screen

_PUTIMAGE (100, 50)-(900, 550), img, backscr,

SCREEN scr

'#######################################################

'#          Lookup Table for distance                  #

'#######################################################

FOR yp = 0 TO spotLightSize * 2

FOR xp = 0 TO spotLightSize * 2

  distLUT(xp, yp) = SQR(((xp - spotLightSize) ^ 2) + ((yp - spotLightSize) ^ 2))

NEXT

NEXT

'#######################################################

'#                  Main Loop                          #

'#######################################################

xl = _WIDTH / 2: yl = _HEIGHT / 2

DO

CLS

' Scan over the area of the spotlight and lighten the pixel

FOR yp = yl - spotLightSize TO yl + spotLightSize

  FOR xp = xl - spotLightSize TO xl + spotLightSize

  dist = distLUT(xp - xl + spotLightSize, yp - yl + spotLightSize)

  IF dist < spotLightSize THEN

    percentage = clamp((dist / spotLightSize), 0, 1)

    _SOURCE backscr

    colour = colorMixer(POINT(xp, yp), 0, 1 - percentage)

    PSET (xp, yp), colour

  END IF

  NEXT

NEXT

' Mouse routine

DO WHILE _MOUSEINPUT

  xl = _MOUSEX: yl = _MOUSEY

LOOP

_DISPLAY

LOOP



'#######################################################

'#              Helper Functions                      #

'#######################################################

FUNCTION colorChannelMixer%% (colorChannelA AS _UNSIGNED _BYTE, colorChannelB AS _UNSIGNED _BYTE, amountToMix AS DOUBLE)

DIM AS DOUBLE channelA, channelB

channelA = colorChannelA * amountToMix

channelB = colorChannelB * (1 - amountToMix)

colorChannelMixer = INT(channelA + channelB)

END FUNCTION



FUNCTION colorMixer& (rgbA AS LONG, rgbB AS LONG, amountToMix AS DOUBLE)

DIM AS _UNSIGNED _BYTE r, g, b

r = colorChannelMixer(_RED(rgbA), _RED(rgbB), amountToMix)

g = colorChannelMixer(_GREEN(rgbA), _GREEN(rgbB), amountToMix)

b = colorChannelMixer(_BLUE(rgbA), _BLUE(rgbB), amountToMix)

colorMixer = _RGB(r, g, b)

END FUNCTION



FUNCTION clamp# (a AS DOUBLE, hi AS DOUBLE, low AS DOUBLE)

DIM AS DOUBLE NDa

NDa = a

IF hi < low THEN SWAP hi, low

IF NDa < low THEN NDa = low

IF NDa > hi THEN NDa = high

clamp# = NDa

END FUNCTION

[Dav]

Well that works very well also, @justsomeguy.  Good coding.  

This forum is great, so many quick replies with great code!

- Dav