# RGB conversion to and from an Array, broadcasting
**URL:** https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721
**Category:** New to Julia
**Created:** [July 15, 2021, 11:59pm UTC](https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721 "2021-07-15T23:59:43Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)
#### Post date: [July 15, 2021, 11:59pm UTC](https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721/1 "2021-07-15T23:59:43Z")
Hi,
I’ve just had a couple of days with Julia - I’m very much enjoying the Pluto, Jupyter and repl environments. Python has been making me bilious.
I have some very ‘early-learner’ questions related to idioms for unpacking and repacking _single_ `RGB` values. The MIT [Introduction to Computational Thinking](https://computationalthinking.mit.edu/Spring21/) course has a very early exercise to write a function that inverts an `RGB` value. I can do it the blah blah way, but…
A. I know how to make an `RGB `value like this `RGB(-1.0, 0.0, 0.0)`, but I cannot find out how to convert an Array containing the same values to a single `RGB` value.
```nohighlight
v = (-1.0, 0.0, 0.0)
v2 = RGB(v) # I can find no examples
```
B. How do I unpack an `RGB` value into an array, without using `[c.r, c.g. c.b]`?
I’d like to do something like `(r,g,b) = c`, or `c.asArray` - preserving order. _My brackets are in dissaray 🙂_
C. I’m disappointed because I can broadcast an operation over an array, but not over an `RBG` value:
```julia
c = RGB(-1.0, 0.0, 0.0)
v = (c.r, c.g, c.b)
v2 = 1 .- v # Works nicely
# I don't know how to covert back to RGB
```
I would like to be able to do:
```julia
c = RGB(-1.0, 0.0, 0.0)
c2 = 1 -. c
```
I tried looking at `cmap` but there were no examples simple enough for me to interpret at my level.
Cheers…
---
### Author:  [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)
#### Post date: [July 16, 2021, 12:15am UTC](https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721/2 "2021-07-16T00:15:33Z")
To unpack a tuple or array into an RGB value, you can use the [`splat` operator](https://docs.julialang.org/en/v1/manual/faq/#...-splits-one-argument-into-many-different-arguments-in-function-calls) like this:
```julia
julia> v2 = RGB(v...)
RGB{Float64}(-1.0,0.0,0.0)
```
I think you want [`mapc`](https://github.com/JuliaGraphics/ColorTypes.jl#functions), not `cmap`. For your example,
```julia
julia> mapc(v -> 1 - v, c)
RGB{Float64}(2.0,1.0,1.0)
```
---
### Author:  [@banksiaboy](https://discourse.julialang.org/u/banksiaboy)
#### Post date: [July 16, 2021, 2:06am UTC](https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721/3 "2021-07-16T02:06:21Z")
Thanks very much! And there it is in the FAQ. 🤪
An insight as to why broadcast doesn’t work on RGB instances?
---
### Author:  [@mkitti](https://discourse.julialang.org/u/mkitti)
#### Post date: [July 16, 2021, 3:27am UTC](https://discourse.julialang.org/t/rgb-conversion-to-and-from-an-array-broadcasting/64721/4 "2021-07-16T03:27:55Z")
Each RGB instance is supposed to be treated as if it were a scalar value. This makes it easier to broadcast over each RGB value collectively rather than each individual component.
See [GitHub - JuliaGraphics/ColorVectorSpace.jl: Treat colors as if they are n-vectors for the purposes of arithmetic](https://github.com/JuliaGraphics/ColorVectorSpace.jl) if you want to treat it like a vector.