Calculating Image Resolutions in Flex


Photo Scaled 200% inside ImageWell. 50 dpi.

Custom book builders are great rich internet applications that we’ve made at Rain. One core component of custom book builders is allowing users to upload their own photos. The most common user error is uploading and using a photo that cannot be printed at a high quality print resolution. It is our job to let the user know if the image he or she has selected for a particular ImageWell (a rectangle where a photo can be placed) can be printed.

Basics of printing

Printers print according to dpi (dots per inch). Say a 1200 px x 1800 px image is printed onto a 4″ x 6″ sheet of paper. The dpi would then be:

  • width: 1200 px / 4 inches = 300 dpi
  • height: 1800 px / 6 inches = 300 dpi

Print resolutions can vary anywhere from 150 dpi (low/medium quality) to 300 dpi (high quality) and up.

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