Many thanks to Natasha for this suggestion: 

Online Photo Editor (https://www.freeonlinephotoeditor.com/) allows you, with a photo upload or URL for an image, to resize, sharpen and/or rotate images. Several filters and effects are available to enhance your photo: Red Eye Removal, Sepia, Enhance, Sharpen and Polaroid Effect. Afterwards, you can download your photo or save it online. (The maximum size of a picture you upload is about 6MB. Large pictures are automatically resized to 1024x768.)

Flower image modified by Online Photo Editor

Photo cropped and 'cartooned' in Online Photo Editor.