mirror of
https://github.com/gohugoio/hugo.git
synced 2024-12-11 06:04:38 -05:00
162 lines
4.4 KiB
Markdown
162 lines
4.4 KiB
Markdown
---
|
|
title: images.Dither
|
|
description: Returns an image filter that dithers an image.
|
|
categories: []
|
|
keywords: []
|
|
action:
|
|
aliases: []
|
|
related:
|
|
- functions/images/Filter
|
|
- functions/images/Process
|
|
- methods/resource/Colors
|
|
- methods/resource/Filter
|
|
returnType: images.filter
|
|
signatures: ['images.Dither [OPTIONS]']
|
|
toc: true
|
|
---
|
|
|
|
{{< new-in 0.123.0 >}}
|
|
|
|
## Options
|
|
|
|
colors
|
|
: (`string array`) A slice of two or more colors that make up the dithering palette, each expressed as an RGB or RGBA [hexadecimal] value, with or without a leading hash mark. The default values are opaque black (`000000ff`) and opaque white (`ffffffff`).
|
|
|
|
[hexadecimal]: https://developer.mozilla.org/en-US/docs/Web/CSS/hex-color
|
|
|
|
method
|
|
: (`string`) The dithering method. See the [dithering methods](#dithering-methods) section below for a list of the available methods. Default is `FloydSteinberg`.
|
|
|
|
serpentine
|
|
: (`bool`) Applicable to error diffusion dithering methods, serpentine controls whether the error diffusion matrix is applied in a serpentine manner, meaning that it goes right-to-left every other line. This greatly reduces line-type artifacts. Default is `true`.
|
|
|
|
strength
|
|
: (`float`) The strength at which to apply the dithering matrix, typically a value in the range [0, 1]. A value of `1.0` applies the dithering matrix at 100% strength (no modification of the dither matrix). The `strength` is inversely proportional to contrast; reducing the strength increases the contrast. Setting `strength` to a value such as `0.8` can be useful to reduce noise in the dithered image. Default is `1.0`.
|
|
|
|
## Usage
|
|
|
|
Create the options map:
|
|
|
|
```go-html-template
|
|
{{ $opts := dict
|
|
"colors" (slice "222222" "808080" "dddddd")
|
|
"method" "ClusteredDot4x4"
|
|
"strength" 0.85
|
|
}}
|
|
```
|
|
|
|
Create the filter:
|
|
|
|
```go-html-template
|
|
{{ $filter := images.Dither $opts }}
|
|
```
|
|
|
|
Or create the filter using the default settings:
|
|
|
|
```go-html-template
|
|
{{ $filter := images.Dither }}
|
|
```
|
|
|
|
{{% include "functions/images/_common/apply-image-filter.md" %}}
|
|
|
|
## Dithering methods
|
|
|
|
See the [Go documentation] for descriptions of each of the dithering methods below.
|
|
|
|
[Go documentation]: https://pkg.go.dev/github.com/makeworld-the-better-one/dither/v2#pkg-variables
|
|
|
|
Error diffusion dithering methods:
|
|
|
|
- Atkinson
|
|
- Burkes
|
|
- FalseFloydSteinberg
|
|
- FloydSteinberg
|
|
- JarvisJudiceNinke
|
|
- Sierra
|
|
- Sierra2
|
|
- Sierra2_4A
|
|
- Sierra3
|
|
- SierraLite
|
|
- Simple2D
|
|
- StevenPigeon
|
|
- Stucki
|
|
- TwoRowSierra
|
|
|
|
Ordered dithering methods:
|
|
|
|
- ClusteredDot4x4
|
|
- ClusteredDot6x6
|
|
- ClusteredDot6x6_2
|
|
- ClusteredDot6x6_3
|
|
- ClusteredDot8x8
|
|
- ClusteredDotDiagonal16x16
|
|
- ClusteredDotDiagonal6x6
|
|
- ClusteredDotDiagonal8x8
|
|
- ClusteredDotDiagonal8x8_2
|
|
- ClusteredDotDiagonal8x8_3
|
|
- ClusteredDotHorizontalLine
|
|
- ClusteredDotSpiral5x5
|
|
- ClusteredDotVerticalLine
|
|
- Horizontal3x5
|
|
- Vertical5x3
|
|
|
|
## Example
|
|
|
|
This example uses the default dithering options.
|
|
|
|
{{< img
|
|
src="images/examples/zion-national-park.jpg"
|
|
alt="Zion National Park"
|
|
filter="Dither"
|
|
filterArgs=""
|
|
example=true
|
|
>}}
|
|
|
|
## Recommendations
|
|
|
|
Regardless of dithering method, do both of the following to obtain the best results:
|
|
|
|
1. Scale the image _before_ dithering
|
|
2. Output the image to a lossless format such as GIF or PNG
|
|
|
|
The example below does both of these, and it sets the dithering palette to the three most dominant colors in the image.
|
|
|
|
|
|
```go-html-template
|
|
{{ with resources.Get "original.jpg" }}
|
|
{{ $opts := dict
|
|
"method" "ClusteredDotSpiral5x5"
|
|
"colors" (first 3 .Colors)
|
|
}}
|
|
{{ $filters := slice
|
|
(images.Process "resize 800x")
|
|
(images.Dither $opts)
|
|
(images.Process "png")
|
|
}}
|
|
{{ with . | images.Filter $filters }}
|
|
<img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
|
|
{{ end }}
|
|
{{ end }}
|
|
```
|
|
|
|
For best results, if the dithering palette is grayscale, convert the image to grayscale before dithering.
|
|
|
|
```go-html-template
|
|
{{ $opts := dict "colors" (slice "222" "808080" "ddd") }}
|
|
{{ $filters := slice
|
|
(images.Process "resize 800x")
|
|
(images.Grayscale)
|
|
(images.Dither $opts)
|
|
(images.Process "png")
|
|
}}
|
|
{{ with images.Filter $filters . }}
|
|
<img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
|
|
{{ end }}
|
|
```
|
|
|
|
The example above:
|
|
|
|
1. Resizes the image to be 800 px wide
|
|
2. Converts the image to grayscale
|
|
3. Dithers the image using the default (`FloydSteinberg`) dithering method with a grayscale palette
|
|
4. Converts the image to the PNG format
|