When adding or importing images on Modalyst, we generate thumbnails in the following sizes:
'40x40m','44x44m', '64x64m', '100x100m', '231x231m', '684x684m', ‘1024x1024m’ (in pixels)
If the image is smaller than thumbnail size it is filled with white background to meet thumbnail dimensions.
If image is bigger than thumbnail size it is scaled down and filled with white background to meet thumbnail dimensions.
When exporting products to Shopify exported image is the biggest thumbnail 1024x1024px