Even today there are many organizations that rely on fax as a required form of communications. Because of this, receiving faxes is a requirement that much still be met. To do this, many organizations utilize fax services either hosted locally or by a third-party. Many of these services will email received faxes to users as a PDF file.
In a normal facsimile transmission, every other scan-line is skipped. This reduces the amount of data that needs to be sent over the relatively slow connection used to send faxes. To account for the missing scan-lines, the aspect ratio of the pixels is 2:1. It is important to recognize this when displaying the image else you will end up displaying the image incorrectly, making it looked squashed.
Incorrectly Displayed Fax Image
The following image is displayed pixel for pixel from image to screen which assumes that the image’s pixel aspect ratio (2:1) matches the screen’s pixel aspect ratio (1:1). This results in an image that is displayed squashed with half the height it should have when displayed correctly.
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In this example, we load a fax that is embedded in a PDF file and save it as a TIFF. During the process, we ensure that the X and Y resolution of the resulting TIFF matches the that of the FAX in the PDF.