=== by Bob Sutherland ===
This is a series of lessons I have created showing how to resize digital photographs. In each lesson I use a different photo editing program running on a Macintosh computer. With each photo editing program I open a large photograph and then reduce the width of the photo to 1024 pixels. The software should automatically calculate the new height of the photograph to maintain the original width to height aspect ratio. I then investigate the options available for saving or exporting the resized photograph to create a new JPEG and/or TIFF file.
I tried using the free photo editing programs RawTherapee and darktable but I was not able to figure out how to resize a photograph using either of those programs. So far I have not had much success trying to learn how to use these programs for any photo editing task.
I tried using the Photos application by Apple that is factory installed on all new Macintosh computers, iPads and iPhones. The only method that I could find to resize a photograph with Photos on my Macintosh computer was to export the photograph file directly to Apple's Mail application. During the export operation I was given a choice of small, medium or large. Two of those choices create photographs that were much too small. The third choice created a photograph that was too large in comparison to my objective of trying to resize the photograph to a width of 1024 pixels.
I have not created a lesson for RAW Power by Gentlemen Coders for Macintosh computers. There is also a version available for iPad and iPhone mobile devices. In the Macintosh version there is no option within the program menus to resize a photograph. Instead there is an option to resize your photograph as you are exporting it. After mouse clicking on the Export button you will be given an opportunity to type a new filename, choose a file type (JPEG, TIFF or PNG), and an Output Size for your photograph. From a short list I was allowed to choose 1024 pixels for the longest side.
The creator of XnView MP for Windows, Macintosh and Linux computers has created a variety of software programs for many different types of computers and mobile devices including applications designed to resize photographs. You may find a program for your machine on his website that more specifically meets your needs.