Paperclip uses the imagemagick resize options like 100x50> , 100x50<, 100x50# etc to resize images.
See the link what options are available.

• ('!') Ignore Aspect Ratio
• ('>') Only Shrink Larger
• ('<') Only Enlarge Smaller
• ('^') Fill Given Area
• ('%') Percentage Resize
• ('@') Pixel Area Limit
• ('#') Crop thumbnail centrally and ensure the requested dimensions, not documented at imagemagick doc

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