Hex/string/float problem

Blitz3D Forums/Blitz3D Programming/Hex/string/float problem

-Rick-

(Posted 2014) [#1]

I've used a bit of code before that picks the color of a pixel and then breaks it down into its component colors

hired# = (rgb2 And $FF0000)/$10000		; <--- Red value of pixel
higrn# = (rgb2 And $FF00)/$100			; <--- Grn value of pixel
hiblu# = (rgb2 And $FF)					; <--- Blu value of pixel

Now, rather than get my color from a pixel I want to use Constants to store color values and then just set my color from there.

Const RED$ = "$FF0000"
Const GREEN$ = "$00FF00"
Const BLUE$ = "$0000FF"
Const LPINK$ = "$FD89D8"

global done

while not done
     cls()
     if keyhit(1) then done = true
     ExtractColor(LPINK)
     rect 0,0,300,200
     flip()
wend
end

Function ExtractColor(Val$)
     R# = (val And $FF0000)/$10000
     G# = (val And $FF00)/$100
     B# = (val And $FF)
     Color r,g,b
End Function

This keeps giving me a value of 0 for each R,G,B. However, if I replace the 'val' in each line with the hex value of my designated pink color then it works fine. Hex values are a bit beyond my understanding and thought a simple tinker would fix this, but I really don't understand why it works with the actual value but not if I use a string variable with the value.

This works -
R# = ($FD89D8 and $FF0000)/$10000
but this doesn't -
val$ = "$FD89D8"
R# =(val and $FF0000)/$10000

Can anyone explain why and what the solution would be?

xlsior

(Posted 2014) [#2]

You're comparing num instead of val$ ?

num isn't defined anywhere, so it will always be zero.

-Rick-

(Posted 2014) [#3]

Sorry, mixed up two versions I'd tried. Num should be Val. Silly mistake on my part. I've edited it.

xlsior

(Posted 2014) [#4]

Floyd

(Posted 2014) [#5]

Blitz3D has three kinds of variables/constants. Float and Int are numbers, and there are also strings.

The $ symbol marks a value as a string, so s$ is a string variable.
x# is a float and n%, or simply n, is an integer.

There is another use for $, as a prefix for a hexadecimal 'literal' value.

Just as 123 is an integer literal in decimal notation $7B is the same integer value as a hexadecimal literal.

Blitz also auto-converts between the three kinds of values. So if n is an integer variable and we do

n = "123"

the string "123" is converted to integer 123 and assigned to n.

The conversion of string to number stops at the first non-valid character.
So n = "12J3" assigns the value 12 to n.

This string-to-number conversion understands only decimal. I suppose Blitz could recognize the $ prefix and 'switch gears' for hexadecimal, but it doesn't.

That's why n = "$7B" results in n = 0. The conversion stops at $, an invalid symbol in a decimal number.

Here is a working example. All values are integer, except for the string value returned by the Hex$( ) function.

Const RED = $FF0000
Const GREEN = $00FF00
Const BLUE = $0000FF
Const LPINK = $FD89D8


val = LPINK

R = (val And $FF0000)/$10000
G = (val And $FF00)/$100
B = (val And $FF)
Print r
Print b
Print g
Print
Print Hex(r)
Print Hex(g)
Print Hex(b)

WaitKey

-Rick-

(Posted 2014) [#6]

Floyd, thanks for this. I don't know why I had so much trouble. I have to chalk it up to not much experience working directly with hex numbers. I could almost swear I started out as your example but obviously I didn't and made a wrong assumption with it somewhere that led me into the wrong direction.

I knew I was misplacing symbols somewhere and that it was something simple but just couldn't get onto it correctly. You've saved me many hours of head scratching!