iOS Programming: The Big Nerd Ranch Guide, Second Edition

Image Manipulation

To display an image within a cell, you could just resize the large image of the possession from the image store. However, doing so would incur a performance penalty because a large number of bytes would need to be read, filtered, and resized to fit within the cell. A better idea is to create and use a thumbnail of the image instead.

To create a thumbnail of a Possession image, you are going to draw a scaled-down version of the full image to an offscreen context and keep a pointer to that new image inside a Possession instance. You’ll create this thumbnail when you take a photo and save the image for a Possession. However, this application will only create a thumbnail when an image is taken, and, if the user exits the application, ...