Images Go API Overview

The Images API provides the ability to serve images directly from Google Cloud Storage or Blobstore, and to optionally resize or crop those images on the fly. To view the contents of the image package, see the image package reference.

Image formats

The service accepts image data in the JPEG, PNG, WEBP, GIF (including animated GIF), BMP, TIFF and ICO formats.

It can return transformed images in the JPEG, WEBP and PNG formats. If the input format and the output format are different, the service converts the input data to the output format before performing the transformation.

Serving and re-sizing images

The image.ServingURL function allows you to generate a stable, dedicated URL for serving web-suitable image thumbnails. You simply store a single copy of your original image in Blobstore, and then request a high-performance per-image URL. This special URL can serve that image resized and/or cropped automatically, and serving from this URL does not incur any CPU or dynamic serving load on your application (though bandwidth is still charged as usual). Images are served with low latency from a highly optimized, cookieless infrastructure.

The URL returned by the function is always public, but not guessable; private URLs are not currently supported. If you wish to stop serving the URL, delete it using the image.DeleteServingURL function.

If you pass an image.ServingURLOptions value to the function, it returns a URL encoded with those options. If you pass nil, the function returns the default URL for the image, for example:

You can resize and crop the image dynamically by specifying the arguments in the URL. The available arguments are:

  • =sxx where xx is an integer from 0–2560 representing the length, in pixels, of the image's longest side. For example, adding =s32 resizes the image so its longest dimension is 32 pixels.
  • =sxx-c where xx is an integer from 0–2560 representing the cropped image size in pixels, and -c tells the system to crop the image.
# Resize the image to 32 pixels (aspect-ratio preserved)

# Crop the image to 32 pixels

Serving images from Cloud Storage using the Blobstore API

If you use Cloud Storage for image storage, but serve the images with the Blobstore API, you will need to create a blobkey for the Cloud Storage object, as described in Using the Blobstore API with Google Cloud Storage.

A note about deletion

Whether you store your images in Cloud Storage or Blobstore, the right way to stop an image from being publicly accessible through the serving URL is to call the image.DeleteServingURL function.

If you merely delete the underlying stored image from Cloud Storage or Blobstore, under some circumstances the image may remain accessible through the serving URL.

Serving URLs will stop working if the application that created them is disabled or deleted, even if the underlying image remains available.

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