images.Dither

Returns an image filter that dithers an image.

Syntax

images.Dither [OPTIONS]

Returns

images.filter

Options

colors: ([]string) 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).

method: (string) The dithering method. See the dithering methods section below for a list of the available methods. Default is FloydSteinberg.
serpentine: (bool) Applicable to error diffusion dithering methods, whether to apply the error diffusion matrix 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:

{{ $opts := dict
  "colors" (slice "222222" "808080" "dddddd")
  "method" "ClusteredDot4x4"
  "strength" 0.85
}}

Create the filter:

{{ $filter := images.Dither $opts }}

Or create the filter using the default settings:

{{ $filter := images.Dither }}

使用 images.Filter 函數應用濾鏡：

{{ with resources.Get "images/original.jpg" }}
  {{ with . | images.Filter $filter }}
    <img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
  {{ end }}
{{ end }}

您也可以使用 Resource 對象上的 Filter 方法應用濾鏡：

{{ with resources.Get "images/original.jpg" }}
  {{ with .Filter $filter }}
    <img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
  {{ end }}
{{ end }}
{{__hugo_ctx/}}



## 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.



  Original
  
  Processed
  

## Recommendations

Regardless of dithering method, do both of the following to obtain the best results:

1. Scale the image _before_ dithering
1. 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.

{{ $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:

Resizes the image to be 800 px wide
Converts the image to grayscale
Dithers the image using the default (FloydSteinberg) dithering method with a grayscale palette
Converts the image to the PNG format

Last updated: January 1, 0001

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