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IVM Concepts

To understand this API's various URL resources and the data they exchange, you need to familiarize yourself with these concepts:

  • Preset Transformations: Image and Video Manager automatically transforms a website's images by creating derivative images of various sizes and formats, and dynamically selecting the appropriate image when requested by an end user. You can create policies to modify how a website's images are transformed.

  • On-Demand Transformations: Image and Video Manager also supports on-demand transformations, using query string parameters. These parameters allow you to specify which derivative image to select, force the selection of a particular output format, or specify a different policy.

  • API Key: Like other Akamai APIs, this API uses hostname tokens to authenticate requests. However, in this API you need to pass in an additional Luna-Token header with each request. You get this key from the Image and Video Manager behavior in your Property Manager configuration that applies to the set of images you're working on.

  • Policy: A policy is a set of specifications applied to a derivative image. Policies may contain information about the image sizes to use for various screens, desired output formats (WebP, JPEG, and PNG), and image manipulations like watermarks. After a policy is applied to a derivative image, Image and Video Manager transforms the image based on the information in that policy.

  • Default Policy: Image and Video Manager automatically applies the default .auto policy unless a request includes a parameter indicating a valid custom policy name. It provides the baseline settings that determine how the policy generates derivatives. You can modify the .auto policy to select different image transformations, but you can't delete it. The .auto policy is always active on both the staging and production networks. By default, the .auto policy has a quality setting of 85. The default image widths in pixels are 320, 640, 1024, 2048, and 5000.

  • Cache Key: Image and Video Manager adds the policy name and version to an image's cache key. Be aware that any policy modification invalidates any images using the policy. For the default policy, this may cause an unexpected surge in traffic to your origin image content. You should test out any policy changes in the Akamai staging network. Once you complete testing, activate the policy in production.

  • Transformations: Each policy specifies a set of transformations to perform on a source image. Some transformations are only performed if certain conditions are met. See Transformation types for more information.

  • Variables: Within a policy, you can define a set of variables that supply the values to use with transformations.

  • Quality (default): Using a quality value from 1-100 resembles JPEG quality across output formats. The default is 85.

  • Perceptual Quality: Dynamically tunes the quality parameter for each image format based on the human-perceived quality of the output image. For better byte savings without compromising perception of the image, use perceptualQuality instead of quality to encode many images at a much lower quality. For certain images that need to maintain human-perceived quality, encode them at a slightly higher quality.