Programming Python, 3rd Edition

PyPhoto: An Image Viewer and Resizer

In Chapter 10, we wrote a simple thumbnail image viewer that scrolled its thumbnails in a canvas. That program in turn built on techniques and code we developed at the end of Chapter 9 to handle images. In both places, I promised that we’d eventually meet a more full-featured extension of the ideas we deployed.

In this section, we finally wrap up the thumbnail images thread by studying PyPhoto—an enhanced image viewing and resizing program. PyPhoto’s basic operation is straightforward: given a directory of image files, PyPhoto displays their thumbnails in a scrollable canvas. When a thumbnail is selected, the corresponding image is displayed full size in a pop-up window.

Unlike our prior viewers, though, PyPhoto is clever enough to scroll (rather than crop) images too large for the physical display. Moreover, PyPhoto introduces the notion of image resizing—it supports mouse and keyboard events that resize the image to one of the display’s dimensions and zoom the image in and out. Once images are opened, the resizing logic allows images to be grown or shrunk arbitrarily, which is especially handy for images produced by a digital camera that may be too large to view all at once.

As added touches, PyPhoto also allows the image to be saved in a file (possibly after being resized), and it allows an image directory to be selected and opened in the GUI itself, instead of just as a command-line argument.

Put together, PyPhoto’s features make it an image-processing ...