hugo/resources/images/filters.go
Bjørn Erik Pedersen e197c7b29d Add Luminance to Color
To sort an image's colors from darkest to lightest, you can then do:

```handlebars
{{ {{ $colorsByLuminance := sort $image.Colors "Luminance" }}
```

This uses the formula defined here: https://www.w3.org/TR/WCAG21/#dfn-relative-luminance

Fixes #10450
2024-04-16 10:02:46 +02:00

382 lines
12 KiB
Go

// Copyright 2024 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 provides template functions for manipulating images.
package images
import (
"fmt"
"image/color"
"strings"
"github.com/gohugoio/hugo/common/hugio"
"github.com/gohugoio/hugo/common/maps"
"github.com/gohugoio/hugo/resources/resource"
"github.com/makeworld-the-better-one/dither/v2"
"github.com/mitchellh/mapstructure"
"github.com/disintegration/gift"
"github.com/spf13/cast"
)
// Increment for re-generation of images using these filters.
const filterAPIVersion = 0
type Filters struct{}
// Process creates a filter that processes an image using the given specification.
func (*Filters) Process(spec any) gift.Filter {
return filter{
Options: newFilterOpts(spec),
Filter: processFilter{
spec: cast.ToString(spec),
},
}
}
// Overlay creates a filter that overlays src at position x y.
func (*Filters) Overlay(src ImageSource, x, y any) gift.Filter {
return filter{
Options: newFilterOpts(src.Key(), x, y),
Filter: overlayFilter{src: src, x: cast.ToInt(x), y: cast.ToInt(y)},
}
}
// Opacity creates a filter that changes the opacity of an image.
// The opacity parameter must be in range (0, 1).
func (*Filters) Opacity(opacity any) gift.Filter {
return filter{
Options: newFilterOpts(opacity),
Filter: opacityFilter{opacity: cast.ToFloat32(opacity)},
}
}
// Text creates a filter that draws text with the given options.
func (*Filters) Text(text string, options ...any) gift.Filter {
tf := textFilter{
text: text,
color: color.White,
size: 20,
x: 10,
y: 10,
linespacing: 2,
}
var opt maps.Params
if len(options) > 0 {
opt = maps.MustToParamsAndPrepare(options[0])
for option, v := range opt {
switch option {
case "color":
if color, ok, _ := toColorGo(v); ok {
tf.color = color
}
case "size":
tf.size = cast.ToFloat64(v)
case "x":
tf.x = cast.ToInt(v)
case "y":
tf.y = cast.ToInt(v)
case "linespacing":
tf.linespacing = cast.ToInt(v)
case "font":
if err, ok := v.(error); ok {
panic(fmt.Sprintf("invalid font source: %s", err))
}
fontSource, ok1 := v.(hugio.ReadSeekCloserProvider)
identifier, ok2 := v.(resource.Identifier)
if !(ok1 && ok2) {
panic(fmt.Sprintf("invalid text font source: %T", v))
}
tf.fontSource = fontSource
// The input value isn't hashable and will not make a stable key.
// Replace it with a string in the map used as basis for the
// hash string.
opt["font"] = identifier.Key()
}
}
}
return filter{
Options: newFilterOpts(text, opt),
Filter: tf,
}
}
// Padding creates a filter that resizes the image canvas without resizing the
// image. The last argument is the canvas color, expressed as an RGB or RGBA
// hexadecimal color. The default value is `ffffffff` (opaque white). The
// preceding arguments are the padding values, in pixels, using the CSS
// shorthand property syntax. Negative padding values will crop the image. The
// signature is images.Padding V1 [V2] [V3] [V4] [COLOR].
func (*Filters) Padding(args ...any) gift.Filter {
if len(args) < 1 || len(args) > 5 {
panic("the padding filter requires between 1 and 5 arguments")
}
var top, right, bottom, left int
var ccolor color.Color = color.White // canvas color
_args := args // preserve original args for most stable hash
if vcs, ok, err := toColorGo(args[len(args)-1]); ok || err != nil {
if err != nil {
panic("invalid canvas color: specify RGB or RGBA using hex notation")
}
ccolor = vcs
args = args[:len(args)-1]
if len(args) == 0 {
panic("not enough arguments: provide one or more padding values using the CSS shorthand property syntax")
}
}
var vals []int
for _, v := range args {
vi := cast.ToInt(v)
if vi > 5000 {
panic("padding values must not exceed 5000 pixels")
}
vals = append(vals, vi)
}
switch len(args) {
case 1:
top, right, bottom, left = vals[0], vals[0], vals[0], vals[0]
case 2:
top, right, bottom, left = vals[0], vals[1], vals[0], vals[1]
case 3:
top, right, bottom, left = vals[0], vals[1], vals[2], vals[1]
case 4:
top, right, bottom, left = vals[0], vals[1], vals[2], vals[3]
default:
panic(fmt.Sprintf("too many padding values: received %d, expected maximum of 4", len(args)))
}
return filter{
Options: newFilterOpts(_args...),
Filter: paddingFilter{
top: top,
right: right,
bottom: bottom,
left: left,
ccolor: ccolor,
},
}
}
// Dither creates a filter that dithers an image.
func (*Filters) Dither(options ...any) gift.Filter {
ditherOptions := struct {
Colors []any
Method string
Serpentine bool
Strength float32
}{
Method: "floydsteinberg",
Serpentine: true,
Strength: 1.0,
}
if len(options) != 0 {
err := mapstructure.WeakDecode(options[0], &ditherOptions)
if err != nil {
panic(fmt.Sprintf("failed to decode options: %s", err))
}
}
if len(ditherOptions.Colors) == 0 {
ditherOptions.Colors = []any{"000000ff", "ffffffff"}
}
if len(ditherOptions.Colors) < 2 {
panic("palette must have at least two colors")
}
var palette []color.Color
for _, c := range ditherOptions.Colors {
cc, ok, err := toColorGo(c)
if !ok || err != nil {
panic(fmt.Sprintf("%q is an invalid color: specify RGB or RGBA using hexadecimal notation", c))
}
palette = append(palette, cc)
}
d := dither.NewDitherer(palette)
if method, ok := ditherMethodsErrorDiffusion[strings.ToLower(ditherOptions.Method)]; ok {
d.Matrix = dither.ErrorDiffusionStrength(method, ditherOptions.Strength)
d.Serpentine = ditherOptions.Serpentine
} else if method, ok := ditherMethodsOrdered[strings.ToLower(ditherOptions.Method)]; ok {
d.Mapper = dither.PixelMapperFromMatrix(method, ditherOptions.Strength)
} else {
panic(fmt.Sprintf("%q is an invalid dithering method: see documentation", ditherOptions.Method))
}
return filter{
Options: newFilterOpts(ditherOptions),
Filter: ditherFilter{ditherer: d},
}
}
// AutoOrient creates a filter that rotates and flips an image as needed per
// its EXIF orientation tag.
func (*Filters) AutoOrient() gift.Filter {
return filter{
Filter: autoOrientFilter{},
}
}
// Brightness creates a filter that changes the brightness of an image.
// The percentage parameter must be in range (-100, 100).
func (*Filters) Brightness(percentage any) gift.Filter {
return filter{
Options: newFilterOpts(percentage),
Filter: gift.Brightness(cast.ToFloat32(percentage)),
}
}
// ColorBalance creates a filter that changes the color balance of an image.
// The percentage parameters for each color channel (red, green, blue) must be in range (-100, 500).
func (*Filters) ColorBalance(percentageRed, percentageGreen, percentageBlue any) gift.Filter {
return filter{
Options: newFilterOpts(percentageRed, percentageGreen, percentageBlue),
Filter: gift.ColorBalance(cast.ToFloat32(percentageRed), cast.ToFloat32(percentageGreen), cast.ToFloat32(percentageBlue)),
}
}
// Colorize creates a filter that produces a colorized version of an image.
// The hue parameter is the angle on the color wheel, typically in range (0, 360).
// The saturation parameter must be in range (0, 100).
// The percentage parameter specifies the strength of the effect, it must be in range (0, 100).
func (*Filters) Colorize(hue, saturation, percentage any) gift.Filter {
return filter{
Options: newFilterOpts(hue, saturation, percentage),
Filter: gift.Colorize(cast.ToFloat32(hue), cast.ToFloat32(saturation), cast.ToFloat32(percentage)),
}
}
// Contrast creates a filter that changes the contrast of an image.
// The percentage parameter must be in range (-100, 100).
func (*Filters) Contrast(percentage any) gift.Filter {
return filter{
Options: newFilterOpts(percentage),
Filter: gift.Contrast(cast.ToFloat32(percentage)),
}
}
// Gamma creates a filter that performs a gamma correction on an image.
// The gamma parameter must be positive. Gamma = 1 gives the original image.
// Gamma less than 1 darkens the image and gamma greater than 1 lightens it.
func (*Filters) Gamma(gamma any) gift.Filter {
return filter{
Options: newFilterOpts(gamma),
Filter: gift.Gamma(cast.ToFloat32(gamma)),
}
}
// GaussianBlur creates a filter that applies a gaussian blur to an image.
func (*Filters) GaussianBlur(sigma any) gift.Filter {
return filter{
Options: newFilterOpts(sigma),
Filter: gift.GaussianBlur(cast.ToFloat32(sigma)),
}
}
// Grayscale creates a filter that produces a grayscale version of an image.
func (*Filters) Grayscale() gift.Filter {
return filter{
Filter: gift.Grayscale(),
}
}
// Hue creates a filter that rotates the hue of an image.
// The hue angle shift is typically in range -180 to 180.
func (*Filters) Hue(shift any) gift.Filter {
return filter{
Options: newFilterOpts(shift),
Filter: gift.Hue(cast.ToFloat32(shift)),
}
}
// Invert creates a filter that negates the colors of an image.
func (*Filters) Invert() gift.Filter {
return filter{
Filter: gift.Invert(),
}
}
// Pixelate creates a filter that applies a pixelation effect to an image.
func (*Filters) Pixelate(size any) gift.Filter {
return filter{
Options: newFilterOpts(size),
Filter: gift.Pixelate(cast.ToInt(size)),
}
}
// Saturation creates a filter that changes the saturation of an image.
func (*Filters) Saturation(percentage any) gift.Filter {
return filter{
Options: newFilterOpts(percentage),
Filter: gift.Saturation(cast.ToFloat32(percentage)),
}
}
// Sepia creates a filter that produces a sepia-toned version of an image.
func (*Filters) Sepia(percentage any) gift.Filter {
return filter{
Options: newFilterOpts(percentage),
Filter: gift.Sepia(cast.ToFloat32(percentage)),
}
}
// Sigmoid creates a filter that changes the contrast of an image using a sigmoidal function and returns the adjusted image.
// It's a non-linear contrast change useful for photo adjustments as it preserves highlight and shadow detail.
func (*Filters) Sigmoid(midpoint, factor any) gift.Filter {
return filter{
Options: newFilterOpts(midpoint, factor),
Filter: gift.Sigmoid(cast.ToFloat32(midpoint), cast.ToFloat32(factor)),
}
}
// UnsharpMask creates a filter that sharpens an image.
// The sigma parameter is used in a gaussian function and affects the radius of effect.
// Sigma must be positive. Sharpen radius roughly equals 3 * sigma.
// The amount parameter controls how much darker and how much lighter the edge borders become. Typically between 0.5 and 1.5.
// The threshold parameter controls the minimum brightness change that will be sharpened. Typically between 0 and 0.05.
func (*Filters) UnsharpMask(sigma, amount, threshold any) gift.Filter {
return filter{
Options: newFilterOpts(sigma, amount, threshold),
Filter: gift.UnsharpMask(cast.ToFloat32(sigma), cast.ToFloat32(amount), cast.ToFloat32(threshold)),
}
}
type filter struct {
Options filterOpts
gift.Filter
}
// For cache-busting.
type filterOpts struct {
Version int
Vals any
}
func newFilterOpts(vals ...any) filterOpts {
return filterOpts{
Version: filterAPIVersion,
Vals: vals,
}
}