Uploading large images to Cloudinary (or any other cloud-service) involves overcoming challenges such as high storage consumption and a long upload duration. While the former can be tackled (on the server-side) with our incoming-transformation feature, the latter requires client-side intervention to resize the image before upload.
Cloudinary offers client-side resizing as a service with the jQuery upload plugin. Setup instructions are given here: https://github.com/cloudinary/cloudinary_js#client-side-image-resizing-before-upload
We also plan to support this approach on our Mobile SDKs (Android and iOS) as well. In the meantime we invite our users to use 3rd party libraries to achieve the same results and streamline the upload process.