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layer.go
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layer.go
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package ring
import (
"fmt"
"image/color"
"math"
)
// Layer represents a drawable layer of the LED ring.
type Layer struct {
pixels []color.Color
pixArc float64 // pixel arc in radians
rotFloat float64 // float part of rotation in radians
rotInt int // integer part of rotation in radians
opt *LayerOptions
buffer []color.Color
}
// LayerOptions is the list of options of a layer.
type LayerOptions struct {
// Resolution sets the number of pixels a layer has. Usually, this is set
// to the same number of LEDs the ring has.
Resolution int
// ContentMode sets how the layer will be rendered (default: Tile).
ContentMode ContentMode
}
// ContentMode defines how the layer will be rendered.
type ContentMode uint8
const (
// ContentTile sets the layer to crop its content if it is larger that the ring
// and to repeat the content.
ContentTile ContentMode = iota
// ContentCrop sets the layer to crop its content if it is larger than the ring
// and does not repeat the content.
ContentCrop
// ContentScale sets the layer to scale up or down its content to fit the ring.
ContentScale
)
// NewLayer creates a new drawable layer.
func NewLayer(options *LayerOptions) (*Layer, error) {
if options.Resolution == 0 {
return nil, fmt.Errorf("ring: resolution of new layer is 0")
}
l := &Layer{
pixels: make([]color.Color, options.Resolution),
buffer: make([]color.Color, options.Resolution),
pixArc: 2 * math.Pi / float64(options.Resolution),
opt: options,
}
l.SetAll(color.Transparent)
l.update()
return l, nil
}
// SetAll sets all the pixels of a layer to an uniform color.
func (l *Layer) SetAll(c color.Color) {
for i := range l.pixels {
l.pixels[i] = c
}
l.update()
}
// SetPixel sets the color of a single pixel in the layer.
func (l *Layer) SetPixel(i int, c color.Color) {
l.pixels[i] = c
l.update()
}
// Rotate sets the rotation of the layer. A positive angle makes a counter-clockwise rotation.
func (l *Layer) Rotate(angle float64) {
rotArc := angle / l.pixArc
rotInt := math.Floor(rotArc)
l.rotFloat = rotArc - rotInt
l.rotInt = int(rotInt)
l.update()
}
// pixelRotated returns the color of the pixel at position i adjusted for the
// rotation of the layer.
func (l *Layer) pixelRotated(i int) (c color.Color) {
i += l.rotInt
c = blendLerp(l.pixelRaw(i), l.pixelRaw(i+1), l.rotFloat)
return c
}
// Pixel returns the color of the pixel at position i, with layer
// transformations.
func (l *Layer) Pixel(i int) (c color.Color) {
return l.buffer[mod(i, l.opt.Resolution)]
}
// Options returns the options of the layer.
func (l *Layer) Options() *LayerOptions {
return l.opt
}
func (l *Layer) update() {
for i := range l.pixels {
l.buffer[i] = l.pixelRotated(i)
}
}
// pixelRaw returns the color of the pixelRaw at position i.
func (l *Layer) pixelRaw(i int) (c color.Color) {
return l.pixels[mod(i, l.opt.Resolution)]
}
func mod(p, n int) (r int) {
r = p % n
if r < 0 {
r += n
}
return r
}