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// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package images
import (
"encoding/hex"
"fmt"
"hash/fnv"
"image/color"
"math"
"strings"
"github.com/gohugoio/hugo/common/hstrings"
)
type colorGoProvider interface {
ColorGo() color.Color
}
type Color struct {
// The color.
color color.Color
// The color prefixed with a #.
hex string
// The relative luminance of the color.
luminance float64
}
// Luminance as defined by w3.org.
// See https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
func (c Color) Luminance() float64 {
return c.luminance
}
// ColorGo returns the color as a color.Color.
// For internal use only.
func (c Color) ColorGo() color.Color {
return c.color
}
// ColorHex returns the color as a hex string prefixed with a #.
func (c Color) ColorHex() string {
return c.hex
}
// String returns the color as a hex string prefixed with a #.
func (c Color) String() string {
return c.hex
}
// For hashstructure. This struct is used in template func options
// that needs to be able to hash a Color.
// For internal use only.
func (c Color) Hash() (uint64, error) {
h := fnv.New64a()
h.Write([]byte(c.hex))
return h.Sum64(), nil
}
func (c *Color) init() error {
c.hex = ColorGoToHexString(c.color)
r, g, b, _ := c.color.RGBA()
c.luminance = 0.2126*c.toSRGB(uint8(r)) + 0.7152*c.toSRGB(uint8(g)) + 0.0722*c.toSRGB(uint8(b))
return nil
}
func (c Color) toSRGB(i uint8) float64 {
v := float64(i) / 255
if v <= 0.04045 {
return v / 12.92
} else {
return math.Pow((v+0.055)/1.055, 2.4)
}
}
// AddColorToPalette adds c as the first color in p if not already there.
// Note that it does no additional checks, so callers must make sure
// that the palette is valid for the relevant format.
func AddColorToPalette(c color.Color, p color.Palette) color.Palette {
var found bool
for _, cc := range p {
if c == cc {
found = true
break
}
}
if !found {
p = append(color.Palette{c}, p...)
}
return p
}
// ReplaceColorInPalette will replace the color in palette p closest to c in Euclidean
// R,G,B,A space with c.
func ReplaceColorInPalette(c color.Color, p color.Palette) {
p[p.Index(c)] = c
}
// ColorGoToHexString converts a color.Color to a hex string.
func ColorGoToHexString(c color.Color) string {
r, g, b, a := c.RGBA()
rgba := color.RGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
if rgba.A == 0xff {
return fmt.Sprintf("#%.2x%.2x%.2x", rgba.R, rgba.G, rgba.B)
}
return fmt.Sprintf("#%.2x%.2x%.2x%.2x", rgba.R, rgba.G, rgba.B, rgba.A)
}
// ColorGoToColor converts a color.Color to a Color.
func ColorGoToColor(c color.Color) Color {
cc := Color{color: c}
if err := cc.init(); err != nil {
panic(err)
}
return cc
}
func hexStringToColor(s string) Color {
c, err := hexStringToColorGo(s)
if err != nil {
panic(err)
}
return ColorGoToColor(c)
}
// HexStringsToColors converts a slice of hex strings to a slice of Colors.
func HexStringsToColors(s ...string) []Color {
var colors []Color
for _, v := range s {
colors = append(colors, hexStringToColor(v))
}
return colors
}
func toColorGo(v any) (color.Color, bool, error) {
switch vv := v.(type) {
case colorGoProvider:
return vv.ColorGo(), true, nil
default:
s, ok := hstrings.ToString(v)
if !ok {
return nil, false, nil
}
c, err := hexStringToColorGo(s)
if err != nil {
return nil, false, err
}
return c, true, nil
}
}
func hexStringToColorGo(s string) (color.Color, error) {
s = strings.TrimPrefix(s, "#")
if len(s) != 3 && len(s) != 4 && len(s) != 6 && len(s) != 8 {
return nil, fmt.Errorf("invalid color code: %q", s)
}
s = strings.ToLower(s)
if len(s) == 3 || len(s) == 4 {
var v string
for _, r := range s {
v += string(r) + string(r)
}
s = v
}
// Standard colors.
if s == "ffffff" {
return color.White, nil
}
if s == "000000" {
return color.Black, nil
}
// Set Alfa to white.
if len(s) == 6 {
s += "ff"
}
b, err := hex.DecodeString(s)
if err != nil {
return nil, err
}
return color.RGBA{b[0], b[1], b[2], b[3]}, nil
}
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