While Macs don’t come with a specific image editing application, you can use both iPhoto and Preview to perform some basic tasks. Preview is very useful for quickly cropping, resizing and compressing images. A typical need is to open an image, crop it to a certain area, resize it, and then save it out as a compressed file suitable for email or Web display.
You can find Preview in your Application folder. Run it and open any image file. The image will open up and display in a window. You will find a simple toolbar at the top of the window. Click on the Select tool, and make sure it is set to select a rectangular area. Then click and drag a rectangular area matching the portion of the image you want to keep. Then select Tools, Crop or use the keyboard shortcut Command+K. This will get rid of the part of the image outside the selection.
Next, to resize the image, choose Tools, Adjust Size. You will get a control over the window that lets you set the new width and height of the image. You can choose to use different units, such as inches or pixels. You can also check or uncheck “Scale proportionally” to lock the width and height and maintain the same proportions of the original image. DO not worry, however, about the “Resolution” option, as it is not a factor in email or Web-based images. Use 72 pixels/inch as a standard measurement.
After you have cropped and resized the image, you can save it using a standard image format like JPEG. This format will shank the image’s file size considerably, only sacrificing a little quality. Choose File, Save As from the menu bar. At the bottom of the file dialog controller, look for the “Format” pull-down men and choose JPEG. Under that, set the quality. Somewhere between halfway and “Best” is usually a good choice.
Save the file out with a new name, keeping the “.jpg” file extension. You can now use this cropped, resized and compressed image to send in an email message or upload to a Web site. In many cases, this file will be considerably smaller than the original image, making it easier for others to download and view it. For instance, a photo taken with a modern digital camera may start out at 3MB, but once cropped, resized and compressed can be as little as 100KB or less, or about 3% of the original file size.
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