Time for action – flipping

Imagine that you are building a symmetric image using a bunch of basic shapes. To create such an image, an operation that can flip (or mirror) the image would come in handy. So let's see how image flipping can be accomplished.

1. Write the following code in a Python source file.

   1 import Image
   2 inPath = "C:\\images\\Flip.png"
   3 img = Image.open(inPath)
   4 outPath = "C:\\images\\Flip_out.png"
   5 foo = img.transpose(Image.FLIP_LEFT_RIGHT)
   6 foo.save(outPath)

2. In this code, the image is flipped horizontally by calling the transpose method. To flip the image vertically, replace line 5 in the code with the following:

   foo = img.transpose(Image.FLIP_TOP_BOTTOM)

3. The following illustration shows the output of the preceding code when the image is flipped horizontally and vertically.
   
4. The same effect can be achieved using the ImageOps module. To flip the image horizontally, use ImageOps.mirror, and to flip the image vertically, use ImageOps.flip.

   import ImageOps
   
   # Flip image horizontally
   foo1 = ImageOps.mirror(img)
   # Flip image vertically
   foo2 = ImageOps.flip(img)

What just happened?

With the help of example, we learned how to flip an image horizontally or vertically using Image.transpose and also by using methods in class ImageOps. This operation will be applied later in this book for further image processing such as preparing composite images.

Capturing screenshots

How do you capture the desktop screen or a part of it using Python? There is ImageGrab module in PIL. This simple line of code will capture the whole screen.

img = ImageGrab.grab()

Where, img is an instance of class Image.

However, note that in PIL Version 1.1.6, the ImageGrab module supports screen grabbing only for Windows platform.