Slimsy

Effortless Responsive & Lazy Images with LazySizes and Umbraco

Slimsy v6 is made for Umbraco v14+!

Slimsy v5 is made for Umbraco v13.2 < v14!

Slimsy v4 is made for Umbraco v10, v11 & v12!

Release Downloads

NuGet Package:

Prerelease Downloads

NuGet Package:

Installation

1. Install from NuGet

2. Add .AddSlimsy() to program.cs before the call to the .Build() method

e.g.

builder.CreateUmbracoBuilder()
    .AddBackOffice()
    .AddWebsite()
    .AddDeliveryApi()
    .AddComposers()
    .AddSlimsy()
    .Build();

3. Add to _ViewImports.cshtml

@using Slimsy.Enums;
@addTagHelper *, Slimsy
@inject Slimsy.Services.SlimsyService SlimsyService

4. Add lazysizes.min.js & to your templates/views

In your template add the JavaScript files

<script src="/scripts/lazysizes.min.js" async=""></script>

5. Ensure all img elements are set to display: block or display: inline-block;

e.g.

img {
    display:block;
}

If you are using LQIP then you will also need to ensure img elements are set to width:100%;

e.g.

img {
    display:block;
    width:100%;
}

6. Use the <slimsy-picture> tag helper or manually adjust your image elements, adding data-srcset, data-src, sizes="auto" & class="lazyload" attributes

<slimsy-picture media-item="@person.Photo" width="323" height="300" css-class="myClass" render-lqip="true" render-webp-alternative="true"></slimsy-picture>

Use the GetSrcSetUrls UrlHelper extension methods to generate your data-srcset attributes. For these methods to function correctly your image property types should use the built-in Image Cropper.

<div class="employee-grid__item__image">
    <img data-srcset="@Url.GetSrcSetUrls(person.Photo, 323, 300)" srcset="@Url.GetSrcSetUrls(person.Photo, 250, 250, quality: 40)" data-sizes="auto" class="lazyload"/>
</div>

Or inject SlimsyService into your ViewComponents

private readonly SlimsyService _slimsyService;
public ResponsiveImageViewComponent(SlimsyService slimsyService)
{
	_slimsyService = slimsyService;
}

7 (optional). Adjust the rendering of your TinyMce Richtext editors

<div class="col-md-9">
    <article>
        @SlimsyService.ConvertImgToResponsive(Model, "richTextBody", renderPicture:true, pictureSources: new []{"webp"})
    </article>
</div>

8 (optional). Adjust the renderer of media within the Grid editor

There's quite a lot to this - so check it out in the demo site here

Options

Add/Edit appsettings.json

  "Slimsy": {
    "WidthStep": 180,
    "UseCropAsSrc": false,
    "DefaultQuality": 70,
    "Format": "",
    "BackgroundColor": "",
    "AppendSourceDimensions": true,
    "EncodeCommas": true,
    "AutoOrient": true
  }

or edit Startup.cs to modify SlimsyOptions

.AddSlimsy(options =>
{
    options.DefaultQuality = 60;
    options.WidthStep = 60;
    options.UseCropAsSrc = true;
})

TagHelper also has some options in appsettings.json (available in v4.1+)

• SingleSources - allows specific file extensions to only render a single source
• DefaultPictureSources - allows multiple picture sources to be defined, example below is for both avif and webp formats
• ImageDimensions - defines if width and height attributes should be rendered on the img tag

e.g.

  "Slimsy": {
    "WidthStep": 180,
    "UseCropAsSrc": true,
    "DefaultQuality": 70,
    "TagHelper": {
      "SingleSources": [ "gif" ],
      "DefaultPictureSources": [
        {
          "Extension": "avif",
          "Quality": 60
        },
        {
          "Extension": "webp",
          "Quality": 70
        }
      ],
      "ImageDimensions": true
    }
  }

TagHelper has new parameters

• decorative which renders role="presentation" on the img tag
• fetch-priority which renders on the img tag, for example fetchpriority="high"
• image-crop-mode specifies a crop mode such as "Pad"
• image-crop-anchor used with crop-mode to set where cropping should be focussed
• loading (available v4.2+) you can set to Eager to not lazy load, useful for optimzing LCP on the first image rendered on the page

How to use AVIF format in v4.1+

There is not currently a AVIF encoder for ImageSharp, keep an eye on https://github.com/hey-red/ImageSharp.Heif which has amditions of adding a encoder in the future.

Cloudflare Image Resizing does support AVIF encoding and this can be used by Slimsy.

1. Install the CloudflareImageUrlGenerator package

See https://github.com/Jeavon/CloudflareImageUrlGenerator for full details.

dotnet add package Umbraco.Community.CloudflareImageUrlGenerator

2. Add to Startup.cs in the ConfigureServices method

.AddCloudflareImageUrlGenerator()

3. Enable Image Resizing on Cloudflare

https://developers.cloudflare.com/images/image-resizing/enable-image-resizing/

4. Set the avif format as a DefaultPictureSources and enable AppendSourceDimensions in appsettings.json

e.g.

  "Slimsy": {
    "AppendSourceDimensions": true,
    "TagHelper": {
      "DefaultPictureSources": [
        {
          "Extension": "avif",
          "Quality": 60
        },
        {
          "Extension": "webp",
          "Quality": 70
        }
      ]
    }
  }

5. Check the rendered sources

Image paths for avif and webp should begin with /cdn-cgi/image/format=avif,quality=70

Lazysizes.js

Lazysizes.js is awesome and it's part of what makes Slimsy so easy to implement. If you need to find out more information about it or how to hook into it's Javascript events be sure to check out it's GitHub

Test Site & Source Code

A test site is included in the solution, the username and password for Umbraco are [email protected]/password1234567890.

Credits and references

This project includes LazySizes which is MIT licensed.

Without the amazing ImageSharp this package wouldn't exist, so many thanks go to James and all the SixLabors team for creating ImageSharp!

Many thanks to Douglas Robar for naming Slimsy.

Change log

Here