What is the best way to store images in App Engine Blob Storage?

Question

I need to store images in two sizes:
1.Thumbnail (100x200px).
2. Big image (1024x2048).

There are few options of storage:
a) Save original image than resize it dynamically when page is loading by using "Image Manipulation API".
b) Resize original image by "Image Manipulation API" than save two copies in different resolutions.

It seems to me that option a) is using lots of "Frontend Instance Hours". But I don't found any information about how to make option b) work.

Answer 1

You can get it for free using the getServingUrl API.
You upload the image to the blobstore and pass the user a url with the resize params.
The backend will resize the image for you in runtime and save a cached version, you will only pay for the bandwidth.