As part of release 4.8, the Image Picker (which supports jpg, gif or png files) functionality has been enhanced to provide the ability to select SharePoint Image Renditions. This feature allows the content author to upload dimension images and choose image sizing for the Image Picker. This functionality is in addition to the existing add, crop and resize of images.
For any content app where an image can be specified, the Image Picker will be displayed to select an image. Click “Select Image” to open the image picker modal to select an existing image or upload a new image.
Click on an image to highlight your selection. Hover over the select button and click to choose original size or image rendition size.
After choosing the image size and clicking select, the image is added to the current content item.
The below example displays the original image has been added to the content item.
The below example displays the image rendition has been added to the content item.