Compressing images

This article suggests several ways to convert your image files to smaller sizes that are still good enough to use in presentations, etc.

Keeping high resolution photos is fine if you have plenty of hard disk space, but if you include lots of them in a presentation, it will slow down your work and result in a huge file.

Image and photo programs

Specialist programs like Pixelmator or Graphic Converter are often included in special-offer software bundles. These can do what is needed and a great deal more.

However, you can also simply open each image in Apple's wonderful Preview program, then choose File: Save As, and choose a smaller resolution/ file size.

iPhoto is another easy program that you could use. A quick tip is to select multiple hi-res images in iPhoto, then Share: Email, and choose from the simple list of small, medium or large size. This creates an email with lower resolution images attached. Don't send it, just drag the images out and into whatever other program needs them. Of course, if you do want to email smaller versions of your photos, this is a great way to do it.

Keynote

To reduce the file size of an individual image that you’ve masked or resized, select the image and choose Format > Image > Reduce Image File Size. (You must save the Keynote document first.)

To reduce the sizes of all masked and resized (shrunk) images, and shortened videos, choose File > Reduce File Size.

Powerpoint

In PowerPoint 2004 and 2008, there is an option in Preferences to compress graphic files. This pdf from UC Davis, California, explains where to find it. This affects all your photos in all your presentations.

PowerPoint 2011 is more flexible (like Keynote) as it helps you shrink individual images, or all images in a particular presentation. You can click on a graphic/picture, and one option in the toolbar will be "compress". The File menu also has a "Reduce File Size" option, to resize all photos within the presentation. It lets you choose the picture quality and you can crop the non-visible portions of any images.

Credits

Contributed by several people in a discussion on the Mac Ministry List in February 2011.