# gradient proc

Source: https://ref.dm-lang.org/proc/gradient

### Format
- `gradient(Item1, Item2, ..., index)`
- `gradient(Gradient, index)`


### Args
- `Gradient`: A [color gradient](https://ref.dm-lang.org/notes/color-gradient.md) list
- `Item1, Item2...`: Elements of a [color gradient](https://ref.dm-lang.org/notes/color-gradient.md) list
- `index`: The index along the gradient where the interpolation is done.


### Returns
> A color, represented by a text string in #RRGGBB or #RRGGBBAA format

Interpolates between two or more colors along a [color gradient](https://ref.dm-lang.org/notes/color-gradient.md). By default, gradients extend from an index of 0 to 1, but they are allowed to go beyond that if you choose.

The simplest way to use this proc is to interpolate between two colors:

```dm /gradient/
// 20% of the way from red to black
// prints #cc0000 which is rgb(204,0,0)
src << gradient("red", "black", 0.2)
```

Anything that applies to color gradients can be used in this proc, so you can have a looping gradient, or a gradient that uses a color space other than RGB.

In the first format where you specify all the items separately, you can use [named arguments](https://ref.dm-lang.org/proc/arguments/named.md) for `index` and `space` (the gradient's color space). If you don't specify an argument called "index", the last argument is assumed to be the index.

```dm /gradient/
// This gradient loops through all the hues and goes from 0 to 6.
// Because this is a looping gradient, index=10 becomes index=4.
// In HSL, this will give you blue (#0000ff).
src << gradient(0, "#f00", 3, "#0ff", 6, "#f00", "loop", space=COLORSPACE_HSL, index=10)
```

The `gradient(Gradient, index)` format is used for cases where you want to pass an existing gradient to the proc.

```dm /gradient/
var/candy_cane_gradient = list(0.5,"red",0.5,"white","loop")

// the color output alternates between red and white depending on the current time
src << gradient(candy_cane_gradient, world.time/100)
```

### See also
- [Color gradient](https://ref.dm-lang.org/notes/color-gradient.md)
- [rgb proc](https://ref.dm-lang.org/proc/rgb.md)
- [rgb2num proc](https://ref.dm-lang.org/proc/rgb2num.md)
- [Color space](https://ref.dm-lang.org/appendix/color-space.md)