Hugo Images Module

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

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

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

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

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.

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.

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.

External Images

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.

 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

 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'

 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

1{{ partial "images/image" (dict
2  "Page" .
3  "Filename" "/path/to/image.png"
4  "Alt" "Example Image"
5) }}

Site Parameters

 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).

Floating Images to Start (Left)

For example.

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

Floating Images to End (Right)

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)

Specify the Height and Preserve Ratio

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

Specify the Width and Height

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

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

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

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])

Image Filters

Brightness

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

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

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)

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)

Contrast

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

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

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)

GaussianBlur

Applies a gaussian blur to an image.

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

Grayscale

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

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

Invert

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

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

Opacity

Apply a opacity filter on an image.

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

Pixelate

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

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

Saturation

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

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

Sepia

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

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

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)

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)

Examples

Static Images Examples

External Images