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Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 9135

Posted: 07:38pm 19 Mar 2021

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I can see that it's a way to map colours into 8-bit mode, but is there anything to gain over simply having colours in an array. e.g. col(2)=rgb(255,0,0) then using col(2) as the colour? I feel like I must be missing something.

Mick

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matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 11870

Posted: 08:03pm 19 Mar 2021

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In 8-bit mode there are 256 colours available which I have setup using a RGB332 approach (3 bits red, 3 bits green, 2 bits blue). Say you wanted a greyscale image, you could use map to create a full set of 256 grey shades.

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 9135

Posted: 08:28pm 19 Mar 2021

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Ah, so you can use MAP(700) meaning 7 red, 0 green, 0 blue in RGB332, but it might act as RGB(0,255,0) or whatever. The actual number in MAP() is meaningless as a colour, it's simply an 8-bit pointer. I hadn't grasped that...

Thanks. :)

Mick

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twofingers

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Joined: 02/06/2014
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Posted: 08:39pm 19 Mar 2021

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Hi Mixtel90,

I would think the Mandelbrot code is a good example.

Regards
Michael

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TassyJim

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Joined: 07/08/2011
Location: Australia
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Posted: 08:42pm 19 Mar 2021

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Or try this one:

' Set up an array to hold the colour mappings we are going to use
DIM INTEGER cmap(6)

'Clear the screen
CLS

'Set up 6 colours in the array
cmap(1)=RGB(RED)
cmap(2)=RGB(GREEN)
cmap(3)=RGB(BLUE)
cmap(4)=RGB(YELLOW)
cmap(5)=RGB(MAGENTA)
cmap(6)=RGB(CYAN)

' Do an initial update of the CLUT to set up our colours
mapclut

'Display an outer circle in white
CIRCLE MM.HRES/2,MM.VRES/2,MM.VRES/2-1,0,,RGB(WHITE),RGB(WHITE)

' Now draw a simple colour pie chart using our new colours with the ARC command
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,0,60,MAP(1)
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,60,120,MAP(2)
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,120,180,MAP(3)
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,180,240,MAP(4)
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,240,300,MAP(5)
ARC MM.HRES/2,MM.VRES/2,0,MM.VRES/2-10,300,360,MAP(6)

' Start a never ending loop
DO

' each time round the loop move the colours in our array one place to the left
' Use array element 0 to store the first element that is going to be at the end
cmap(0)=cmap(1)
cmap(1)=cmap(2)
cmap(2)=cmap(3)
cmap(3)=cmap(4)
cmap(4)=cmap(5)
cmap(5)=cmap(6)
cmap(6)=cmap(0)

' reset the colour map
mapclut

' pause so we can see the change
PAUSE 200
LOOP

' This subroutine updates the colour map for the colours we are using
' set map positions 1 to 6 to the new colours
' then apply the change
SUB mapclut
MAP(1)=cmap(1)
MAP(2)=cmap(2)
MAP(3)=cmap(3)
MAP(4)=cmap(4)
MAP(5)=cmap(5)
MAP(6)=cmap(6)
MAP set
END SUB

Map allows you to draw a screen then change all the instances of one colour to something different 'instantly'

Jim

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