The photos you see featured in each Keynote theme are actually media placeholders. By dragging your own images or movie files to these placeholders, your media is automatically sized, positioned, and framed to fit the slide’s theme.
To test whether the media on a slide is a placeholder, let the pointer rest over it and see if a help tag appears instructing you to drag your own media file to the placeholder.
To replace a media placeholder with your own image, movie, or audio file, drag it from the Media Browser, the Finder, or another application to the placeholder. For a list of supported file formats, see Importing Images.
To resize or reposition your image within a media placeholder, click the Edit Mask button that hovers over the image after you’ve dropped it onto the placeholder, and then do any of the following:
To resize your image within the placeholder, drag the resize handle above the Edit Mask button.
To reposition your image within the placeholder, position the pointer over the image (the pointer may appear as a hand), and then drag the image to position it where you want.
To replace an item you’ve already placed in a media placeholder, drag a new file to it. You don’t have to delete the old file first.
To reposition a media placeholder on the slide canvas, drag the placeholder to where you want.
To remove a media placeholder from the slide canvas, select the placeholder and press the Delete key.
To learn about creating media placeholders, or converting them to non-placeholders, in order to customize a master slide, see Defining Media Placeholders.