Pi Pano Viewer is a free panoramic image processing SDK developed by Labpano for Android platform. It is a set of software development kits that can process panoramic images with great ease. The SDK is designed to be user-friendly and comes with a plethora of features that make it a comprehensive tool for panoramic image processing.

With Pi Pano Viewer, users can browse pictures, play videos and preview video streams effortlessly. The SDK supports various source modes, including one-eye, two-eye, and full21. It also supports various view modes such as immerse, fisheye, asteroid, cylinder, VR, twoscroll, etc. Additionally, there are several filter effects available such as bleach, charcoal, contours, blueberry, pixelated, etc. Pi Pano Viewer also supports a set of transition animations like flip, fade, gate, circle, fold, etc.

In conclusion, Pi Pano Viewer is a top-of-the-line panoramic image processing SDK that offers a wide range of features. It is a must-have tool for anyone who works with panoramic images. However, it is important to note that the SDK is only available for Android platform.