The images module process images via URL query string and fragment, such as resize, crop, fit, fill and align images. This article offers some use cases for showing how to use it.

Module
github.com/hugomods/images
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Features

  • Process images via URL query string and fragment, such as resizing, aligning, filtering.
  • Convert images in modern format (webp), and reserve the original format as the fallback via <picture>.
  • Lazy loading by default.
  • Set the intrinsic height and width attributes for images to get rid of CLS (Cumulative Layout Shift) affect.
  • Hashing image URLs.

How It Works?

This module was built on top of render-image render hooks.

Installation

hugo.yaml

1module:
2  imports:
3  - path: github.com/hugomods/images

hugo.toml

1[module]
2[[module.imports]]
3    path = 'github.com/hugomods/images'

hugo.json

1{
2   "module": {
3      "imports": [
4         {
5            "path": "github.com/hugomods/images"
6         }
7      ]
8   }
9}

URL Concepts

The URL syntax as follows.

1URL = scheme ":" ["//" authority] path ["?" query] ["#" fragment]

The query string preceded by a question mark (?), and the fragment preceded by a hash (#).

This module uses the query string to process images, and use fragment to align images.

Example
Example caption
For example, ![Example](featured.jpeg?crop=300x120&brightness=-30#float-end "Example caption"), which crop the image in size 300x120, change the brightness as -30 and floating the image to the end (right).

Image Types

Site (Global) Image Resources

The images located in the assets directory.

To use the site/global image resources, you’ll need to put a leading slash (/) into the URL.

PathExample
assets/images/foo.png![Foo](/images/foo.png)
assets/images/bar.png![Bar](/images/bar.png)

Page Image Resources

The images located in the page’s directory.

You’ll need to organize pages as page bundles, for example.

1content/
2  blog/
3    hello/
4      index.md
5      foo.png
6      bar.png

The content structure above includes one page (blog/hello) that contains two image resources: foo.png and bar.png.

Then you can render the images in the page content file (blog/hello/index.md).

1![Foo](foo.png)
2![Bar](bar.png)

Static (Public) Images

The images located in the static folder.

PathExample
static/images/foo.png![Foo](images/foo.png)
static/images/bar.png![Bar](images/bar.png)

External Images

PathExample
https://example.org/images/foo.png![Foo](https://example.org/images/foo.png)
https://example.org/images/bar.png![Bar](https://example.org/images/bar.png)

Limitations

Most of the processing methods work only on site and page image resources, except for alignment and resizing. However, the resizing is implemented by inline styles for static (public) and external images.

The good news is that Hugo allows mounting the static/* folder, to make them to be site resources, then you can process those images via any methods. The advantage is that the source (static) images are always accessible even you haven’t used it.

hugo.yaml

 1module:
 2  mounts:
 3  - source: content
 4    target: content
 5  - source: static
 6    target: static
 7  - source: layouts
 8    target: layouts
 9  - source: data
10    target: data
11  - source: assets
12    target: assets
13  - source: i18n
14    target: i18n
15  - source: archetypes
16    target: archetypes
17  - source: static/uploads
18    target: assets/uploads

hugo.toml

 1[module]
 2[[module.mounts]]
 3    source = 'content'
 4    target = 'content'
 5[[module.mounts]]
 6    source = 'static'
 7    target = 'static'
 8[[module.mounts]]
 9    source = 'layouts'
10    target = 'layouts'
11[[module.mounts]]
12    source = 'data'
13    target = 'data'
14[[module.mounts]]
15    source = 'assets'
16    target = 'assets'
17[[module.mounts]]
18    source = 'i18n'
19    target = 'i18n'
20[[module.mounts]]
21    source = 'archetypes'
22    target = 'archetypes'
23[[module.mounts]]
24    source = 'static/uploads'
25    target = 'assets/uploads'

hugo.json

 1{
 2   "module": {
 3      "mounts": [
 4         {
 5            "source": "content",
 6            "target": "content"
 7         },
 8         {
 9            "source": "static",
10            "target": "static"
11         },
12         {
13            "source": "layouts",
14            "target": "layouts"
15         },
16         {
17            "source": "data",
18            "target": "data"
19         },
20         {
21            "source": "assets",
22            "target": "assets"
23         },
24         {
25            "source": "i18n",
26            "target": "i18n"
27         },
28         {
29            "source": "archetypes",
30            "target": "archetypes"
31         },
32         {
33            "source": "static/uploads",
34            "target": "assets/uploads"
35         }
36      ]
37   }
38}

The configuration example above mounts the static/uploads on assets/uploads, then you’re able to use the images as we did for the site resources.

1![Sample](/uploads/images/sample.jpg?width=300px)

Image Partial

This module offers a images/image partial for theme developers.

Image Partial Parameters

ParameterTypeRequireDefaultDescription
FilenamestringY-The filename or url of image.
Altstring--Alternative text.
Captionstring--Figure Caption.
PagePage--The page variable for finding image resources.
ClassNamestring-img-fluidThe class name of <img>.
Originalboolean-falseWhether to describe the original image info via data-* attributes.
LazyLoadingboolean-trueWhether to enable lazy loading.
1{{ partial "images/image" (dict
2  "Page" .
3  "Filename" "/path/to/image.png"
4  "Alt" "Example Image"
5) }}

Site Parameters

NameTypeDefaultDescription
alignment_center_class_namestringd-block text-centerThe class name of <picture>/<figure> when align to center.
alignment_end_class_namestringfloat-end ms-2The class name of <picture>/<figure> when align to end (right).
alignment_start_class_namestringfloat-start me-2The class name of <picture>/<figure> when align to start (left).
class_namestringimg-fluidThe class name of <img>.
figure_class_namestringfigureThe class name of <figure> when caption is set.
figure_caption_class_namestringfigure-captionThe class name of <figcaption>.
figure_image_class_namestringfigure-imgThis class name will be appended into the <img> class list if caption is set.
modern_formatstringwebpGenerate modern format version of image, empty to disable.
 1params:
 2  hugomods:
 3    images:
 4      alignment_center_class_name: d-block text-center
 5      alignment_end_class_name: float-end ms-2
 6      alignment_start_class_name: float-start me-2
 7      class_name: img-fluid
 8      figure_caption_class_name: figure-caption
 9      figure_class_name: figure
10      figure_image_class_name: figure-img
11      modern_format: webp
 1[params]
 2  [params.hugomods]
 3    [params.hugomods.images]
 4      alignment_center_class_name = 'd-block text-center'
 5      alignment_end_class_name = 'float-end ms-2'
 6      alignment_start_class_name = 'float-start me-2'
 7      class_name = 'img-fluid'
 8      figure_caption_class_name = 'figure-caption'
 9      figure_class_name = 'figure'
10      figure_image_class_name = 'figure-img'
11      modern_format = 'webp'
 1{
 2   "params": {
 3      "hugomods": {
 4         "images": {
 5            "alignment_center_class_name": "d-block text-center",
 6            "alignment_end_class_name": "float-end ms-2",
 7            "alignment_start_class_name": "float-start me-2",
 8            "class_name": "img-fluid",
 9            "figure_caption_class_name": "figure-caption",
10            "figure_class_name": "figure",
11            "figure_image_class_name": "figure-img",
12            "modern_format": "webp"
13         }
14      }
15   }
16}

The class names compatible with Bootstrap v5 by default, you may need adjust it to your CSS if you’re not using Bootstrap.

Aligning Images

We can easily align images by adding URL fragments. Such as #center, #float-start and #float-end represents align center, float start and float end respectively.

Aligning Images to Center

Adding the #center fragment for aligning images to the center.

For example: ![Center](featured.jpeg#center).

Center

Floating Images to Start (Left)

Float Start Adding the #float-start fragment for floating images to the start. You may need to clear to avoid breaking your layout, for Bootstrap users, you could wrap the content inside the bootstrap/clearfix shortcode.

For example.

1{{% bootstrap/clearfix %}}
2![Float Start](featured.jpeg#float-start) TEXTS AROUNDS THE IMAGE.
3{{% /bootstrap/clearfix %}}

Floating Images to End (Right)

Float End Similarly, we can also float images to the end by adding the #float-end fragment.

For example.

1{{% bootstrap/clearfix %}}
2![Float End](featured.jpeg#float-end) TEXTS AROUNDS THE IMAGE.
3{{% /bootstrap/clearfix %}}

Resizing Images

We use the URL query of image for resizing images. For example:

Specify the Width and Preserve Ratio

1![Resize](featured.jpeg?width=300px)

Resize

Specify the Height and Preserve Ratio

1![Resize](featured.jpeg?height=180px)

Resize

Specify the Width and Height

1![Resize](featured.jpeg?width=300px&height=180px)

Resize

Cropping Images

Crop an image to match the given dimensions without resizing. You must provide both width and height. Use the anchor1 option to change the crop box anchor point.

1![Crop Image](featured.jpeg?crop=[width]x[height],[anchor])
  • The size [width]x[height] is required.
  • [anchor] is optional.
Examples
Crop Image
crop=200x200,TopLeft
Crop Image
crop=200x200,Top
Crop Image
crop=200x200,TopRight
Crop Image
crop=200x200,Left
Crop Image
crop=200x200,Center
Crop Image
crop=200x200,Right
Crop Image
crop=200x200,BottomLeft
Crop Image
crop=200x200,Bottom
Crop Image
crop=200x200,BottomRight

Fill Images

Crop and resize an image to match the given dimensions. You must provide both width and height. Use the anchor1 option to change the crop box anchor point.

1![Fill Image](featured.jpeg?fill=[width]x[height],[anchor])
  • The size [width]x[height] is required.
  • [anchor] is optional.
Examples
Fill Image
fill=150x200,TopLeft
Fill Image
fill=150x200,Top
Fill Image
fill=150x200,TopRight
Fill Image
fill=150x200,Left
Fill Image
fill=150x200,Center
Fill Image
fill=150x200,Right
Fill Image
fill=150x200,BottomLeft
Fill Image
fill=150x200,Bottom
Fill Image
fill=150x200,BottomRight

Fitting Images

Downscale an image to fit the given dimensions while maintaining aspect ratio. You must provide both width and height.

1![Fit Image](featured.jpeg?fit=[width]x[height])

Fit Image

Image Filters

Brightness

The brightness must be in range (-100, 100).

1![Image Brightness](featured.jpeg?brightness=-30)

Image Brightness

ColorBalance

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).

1![Image ColorBalance](featured.jpeg?colorBalance=-50,50,150)

Image ColorBalance

Colorize

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).

1![Image Colorize](featured.jpeg?colorize=-100,50,150)

Image Colorize

Contrast

The contrast must be in range (-100, 100).

1![Image Contrast](featured.jpeg?contrast=50)

Image Contrast

Gamma

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.

1![Image Gamma](featured.jpeg?gamma=2)

Image Gamma

GaussianBlur

Applies a gaussian blur to an image.

1![Image GaussianBlur](featured.jpeg?gaussianBlur=2)

Image GaussianBlur

Grayscale

Grayscale creates a filter that produces a grayscale version of an image.

1![Image Grayscale](featured.jpeg?grayscale)

Image Grayscale

Hue

Hue creates a filter that rotates the hue of an image. The hue angle shift is typically in range -180 to 180.

1![Image Hue](featured.jpeg?hue=90)

Image Hue

Invert

Invert creates a filter that negates the colors of an image.

1![Image Invert](featured.jpeg?invert)

Image Invert

Opacity

Apply a opacity filter on an image.

1![Image Opacity](featured.jpeg?opacity=0.5)

Image Opacity

Pixelate

Pixelate creates a filter that applies a pixelation effect to an image.

1![Image Pixelate](featured.jpeg?pixelate=8)

Image Pixelate

Saturation

Saturation creates a filter that changes the saturation of an image.

1![Image Saturation](featured.jpeg?saturation=100)

Image Saturation

Sepia

Sepia creates a filter that produces a sepia-toned version of an image.

1![Image Sepia](featured.jpeg?sepia=200)

Image Sepia

Sigmoid

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.

1![Image Sigmoid](featured.jpeg?sigmoid=2,5)

Image Sigmoid

UnsharpMask

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.

1![Image UnsharpMask](featured.jpeg?unsharpMask=10,1,0.05)

Image UnsharpMask

Examples

Static Images Examples

Static Example

External Images

External Example

SVG Example


  1. When using the Crop or Fill method, the anchor determines the placement of the crop box. You may specify TopLeft, Top, TopRight, Left, Center, Right, BottomLeft, Bottom, BottomRight, or Smart. The default value is Smart↩︎ ↩︎