github.com/kovansky/hugo@v0.92.3-0.20220224232819-63076e4ff19f/resources/images/color.go (about)

     1  // Copyright 2019 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package images
    15  
    16  import (
    17  	"encoding/hex"
    18  	"image/color"
    19  	"strings"
    20  
    21  	"github.com/pkg/errors"
    22  )
    23  
    24  // AddColorToPalette adds c as the first color in p if not already there.
    25  // Note that it does no additional checks, so callers must make sure
    26  // that the palette is valid for the relevant format.
    27  func AddColorToPalette(c color.Color, p color.Palette) color.Palette {
    28  	var found bool
    29  	for _, cc := range p {
    30  		if c == cc {
    31  			found = true
    32  			break
    33  		}
    34  	}
    35  
    36  	if !found {
    37  		p = append(color.Palette{c}, p...)
    38  	}
    39  
    40  	return p
    41  }
    42  
    43  // ReplaceColorInPalette will replace the color in palette p closest to c in Euclidean
    44  // R,G,B,A space with c.
    45  func ReplaceColorInPalette(c color.Color, p color.Palette) {
    46  	p[p.Index(c)] = c
    47  }
    48  
    49  func hexStringToColor(s string) (color.Color, error) {
    50  	s = strings.TrimPrefix(s, "#")
    51  
    52  	if len(s) != 3 && len(s) != 6 {
    53  		return nil, errors.Errorf("invalid color code: %q", s)
    54  	}
    55  
    56  	s = strings.ToLower(s)
    57  
    58  	if len(s) == 3 {
    59  		var v string
    60  		for _, r := range s {
    61  			v += string(r) + string(r)
    62  		}
    63  		s = v
    64  	}
    65  
    66  	// Standard colors.
    67  	if s == "ffffff" {
    68  		return color.White, nil
    69  	}
    70  
    71  	if s == "000000" {
    72  		return color.Black, nil
    73  	}
    74  
    75  	// Set Alfa to white.
    76  	s += "ff"
    77  
    78  	b, err := hex.DecodeString(s)
    79  	if err != nil {
    80  		return nil, err
    81  	}
    82  
    83  	return color.RGBA{b[0], b[1], b[2], b[3]}, nil
    84  }