How can we compress images in DAM AEM6.3?

问题

We are trying to increase the page score (google) for our website. One of the options to do this is "Image optimization".

As we have a huge number of images in the DAM, how can we compress/optimize them? Does AEM have any such tool to achieve this?

ImageMagick is one of the tool to achieve this. Do we need to integrate that with AEM or we'll have to re-upload all the images after compressing them using the tool?

Any suggestions?

回答1:

In contrast to CSS, JS and HTML files which can be gzipped using dispatcher, images can be compressed only by reducing quality or resizing them.

It is a quite common case for AEM projects and there are a couple of options to do that, some of them are coming out-of-the-box and do not even require programming:

• You can extend DAM Update Asset with CreateWebEnabledImageProcess Workflow Process Step. It allows you to generate new image rendition with parameters like size, quality, mime-type. Depending on workflow launcher configuration, this rendition can be generated during creation or modification of assets. You can also trigger the workflow to be run on chosen or all assets.

• In case that CreateWebEnabledImageProcess configuration is not sufficient for your requirements, you can implement your own Workflow Process Step and generate proper rendition programmatically, using for example ImageHelper or some Java framework for images transformation. That might be also needed if you want to generate the compressed images on the fly, for example, instead of generating rendition for each uploaded image, you can implement servlet attached to proper selectors and image extensions (i.e. imageName.mobile.png) which return the compressed image.

• Eventually, integration with ImageMagick is possible, Adobe documentation describes how it can be achieved using CommandLineProcess Workflow Process Step. However, you need to be aware of security vulnerabilities related to this mentioned in the documentation.

It is also worth to mention that if your client needs more advanced solutions for images transformation in the future, then integration with Dynamic Media can also be considered as a possibility, however, this is the most costly solution.

回答2:

There are many ways to optimise Images in AEM. Here I will go through 3 of those ways.

1) Using DAM Update Asset Workflow.

This is an out of the box workflow in AEM, Where on upload of images renditions get created . You can use those renditions path in img src attribute.

2) Using ACS commons Image transformer

Install ACS commons Package , Use Image transformer Servlet config to generate optimised or transformed images acc to requirement. For more Info on this check ACS AEM commons.

3) Using Google PageSpeed in dispatcher level

If you want to reduce the size of image, Google PageSpeed is an option to consider. Install PageSpeed in dispatcher level and add image optimise rules to achieve your requirement. This rule Insights detects the images on the page that can be optimized to reduce their filesize without significantly impacting their visual quality. for more info check here Optimising Images

回答3:

AEM offers options for "image optimisation" but this is a broad topic so there is no "magic" switch you can turn to "optimise" your images. It all boils down to the amount of kilo- or megabytes that are transferred from AEM to the users browser.

The size of an asset is influenced by two things:

1. Asset dimension (width and height).
2. Compression.

The biggest gains can be achieved by simply reducing the assets dimensions. AEM does that already. If you have a look at your assets renditions you will notice that there is not just the so called original rendition but several other renditions with different dimensions.

MyImage.jpg
└── jcr:content
    └── renditions/
        ├── cq5dam.thumbnail.140.100.png
        ├── cq5dam.thumbnail.319.319.png
        ├── cq5dam.thumbnail.48.48.png
        └── original

The numbers in the renditions name are the width and height of the rendition. So there is a version of MyImage.jpg that has a width of 140px and a height of 100px and so on.

This is all done by the DAM Update Asset workflow when the image is uploaded and can be modified to generate more renditions with different dimensions.

But generating images with different dimensions is only half of the story. AEM has to select the rendition with the right dimension at the right moment. This is commonly referred to as "responsive images". The AEM image component does not support "responsive" images out of the box and there are several ways to implement this feature.

The gist of it is that your image component has to contain a list of URLs for different sized renditions. When the page is rendered client side JavaScript determines which rendition is the best for current screen size and adds the URL to the img tags src attribute.

I would recommend that you have a look at the fairly new AEM Core components which are not included with AEM. Those core components contain an image component that supports responsive images. You can read more about those here:

1. AEM Core Components Image Component (GitHub)
2. AEM Core Components Documentation

Usually, components like that will not use "static" renditions that were already generated by the DAM Update Asset workflow but will rely on a Adaptive Image Servlet. This servlet basically gets the asset path and the target width and will return the asset in the requested width. To avoid doing this over and over you should allow the Dispatcher to cache the resulting image.

Those are just the basic things you can do. There are a lot of other things that can be done but all of them with less and less gains in terms of "optimisation".

回答4:

I had the same need, and I looked at ImageMagick too and researched various options. Ultimately I customized the workflows that we use to create our image renditions to integrate with another tool. I modified them to use the Kraken.io API to automatically send the rendition images AEM produced to Kraken where they would be fully web-optimized (using the default Kraken settings). I used their Java integration library to get the basic code for this integration. So eventually I ended up with properly web-optimized images for all the generated renditions (and the same could be done to the original) that were automatically optimized during a workflow without authors having to manually re-upload images. This API usage required a Kraken license.

So I believe the answer is that at this time AEM does not provide a feature to achieve this, and your best bet is to integrate with another tool that does it (custom code).

TinyPng.com was another image optimization service that looked like it would be good for this need and that also had an API.

And for the record, I also submitted this as a feature request to our AEM rep. It seems like a glaring product gap to me, and something I am surprised hasn't been built into the product yet to allow customers to make images fully web-optimized.

来源：https://stackoverflow.com/questions/46121027/how-can-we-compress-images-in-dam-aem6-3