Franklin site has four standard sizes for the image of each object in the archive: original as provided, 1024px wide, 500px wide, 100x100px thumbnail. In the archive/imageImages folder of the site, there are subfolders original, thumbnail, 1024 and 500

For the batch of new images from Parks Canada, I created a new folder for each size containing the original images. I then
cd into the 500 folder
sips --resampleWidth 500 *.jpg [image is 500px wide by Ypx high to maintain aspect ratio of original]
cd into the 1024 folder
sips --resampleWidth 1024 *.jpg [image is 1024px wide by Ypx high to maintain aspect ratio of original]
cd into the thumbnail folder
sips --resampleHeightWidth 100 100 *.jpg [image is 100px wide by 100px high, aspect ratio will be sacrificed - image distorted]

Then I copied those images into the appropriate subfolder in the archive/imageImages folder