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package colors
import (
"fmt"
"image/color"
"math"
"regexp"
"strconv"
"strings"
)
const (
rgbaString = "rgba(%d,%d,%d,%g)"
rgbaCaptureRegexString = "^rgba\\(\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(0\\.[0-9]*|[01])\\s*\\)$"
rgbaCaptureRegexPercentString = "^rgba\\(\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(0\\.[0-9]*|[01])\\s*\\)$"
)
var (
rgbaCaptureRegex = regexp.MustCompile(rgbaCaptureRegexString)
rgbaCapturePercentRegex = regexp.MustCompile(rgbaCaptureRegexPercentString)
)
// RGBAColor represents an RGBA color
type RGBAColor struct {
R uint8
G uint8
B uint8
A float64
}
// ParseRGBA validates an parses the provided string into an RGBAColor object
// supports both RGBA 255 and RGBA as percentages
func ParseRGBA(s string) (*RGBAColor, error) {
s = strings.ToLower(s)
var isPercent bool
vals := rgbaCaptureRegex.FindAllStringSubmatch(s, -1)
if vals == nil || len(vals) == 0 || len(vals[0]) == 0 {
vals = rgbaCapturePercentRegex.FindAllStringSubmatch(s, -1)
if vals == nil || len(vals) == 0 || len(vals[0]) == 0 {
return nil, ErrBadColor
}
isPercent = true
}
r, _ := strconv.ParseUint(vals[0][1], 10, 8)
g, _ := strconv.ParseUint(vals[0][2], 10, 8)
b, _ := strconv.ParseUint(vals[0][3], 10, 8)
a, _ := strconv.ParseFloat(vals[0][4], 64)
if isPercent {
r = uint64(math.Floor(float64(r)/100*255 + .5))
g = uint64(math.Floor(float64(g)/100*255 + .5))
b = uint64(math.Floor(float64(b)/100*255 + .5))
}
return &RGBAColor{R: uint8(r), G: uint8(g), B: uint8(b), A: a}, nil
}
// RGBA validates and returns a new RGBAColor object from the provided r, g, b, a values
func RGBA(r, g, b uint8, a float64) (*RGBAColor, error) {
if a < 0 || a > 1 {
return nil, ErrBadColor
}
return &RGBAColor{R: r, G: g, B: b, A: a}, nil
}
func FromStdColor(c color.Color) *RGBAColor {
r, g, b, a := c.RGBA()
return &RGBAColor{
R: uint8(r >> 8),
G: uint8(g >> 8),
B: uint8(b >> 8),
A: float64(a>>8) / 0xff,
}
}
// String returns the string representation on the RGBAColor
func (c *RGBAColor) String() string {
return fmt.Sprintf(rgbaString, c.R, c.G, c.B, c.A)
}
// ToHEX converts the RGBAColor to a HEXColor
func (c *RGBAColor) ToHEX() *HEXColor {
return &HEXColor{hex: fmt.Sprintf("#%02x%02x%02x", c.R, c.G, c.B)}
}
// ToRGB converts the RGBAColor to an RGBColor
func (c *RGBAColor) ToRGB() *RGBColor {
return &RGBColor{R: c.R, G: c.G, B: c.B}
}
// ToRGBA converts the RGBAColor to an RGBAColor
// it's here to satisfy the Color interface
func (c *RGBAColor) ToRGBA() *RGBAColor {
return c
}
// IsLight returns whether the color is perceived to be a light color
// NOTE: this is determined only by the RGB values, if you need to take
// the alpha into account see the IsLightAlpha function
func (c *RGBAColor) IsLight() bool {
return c.ToRGB().IsLight()
}
// IsDark returns whether the color is perceived to be a dark color
// NOTE: this is determined only by the RGB values, if you need to take
// the alpha into account see the IsLightAlpha function
func (c *RGBAColor) IsDark() bool {
return !c.IsLight()
}
// IsLightAlpha returns whether the color is perceived to be a light color
// based on RGBA values and the provided background color
// algorithm based of of post here: http://stackoverflow.com/a/12228643/3158232
func (c *RGBAColor) IsLightAlpha(bg Color) bool {
// if alpha is 1 then RGB3 == RGB1
if c.A == 1 {
return c.IsLight()
}
// if alpha is 0 then RGB3 == RGB2
if c.A == 0 {
return bg.IsLight()
}
rgb2 := bg.ToRGB()
r1 := float64(c.R)
g1 := float64(c.G)
b1 := float64(c.B)
r2 := float64(rgb2.R)
g2 := float64(rgb2.G)
b2 := float64(rgb2.B)
r3 := r2 + (r1-r2)*c.A
g3 := g2 + (g1-g2)*c.A
b3 := b2 + (b1-b2)*c.A
rgb, _ := RGB(uint8(r3), uint8(g3), uint8(b3))
return rgb.IsLight()
}
// IsDarkAlpha returns whether the color is perceived to be a dark color
// based on RGBA values and the provided background color
// algorithm based of of post here: http://stackoverflow.com/a/12228643/3158232
func (c *RGBAColor) IsDarkAlpha(bg Color) bool {
return !c.IsLightAlpha(bg)
}
|
