Algorithms Used by Google Search

This was a question asked to me by Kalra

• Scale Invariant Feature Transform (SIFT)

For extracting key points and descriptors:

• Principal Component Analysis based Scale Invariant Feature Transform (PCA-SIFT)
• Speeded Up Robust Features (SURF)

For Indexing and matching:

• Locally-sensitive Hashing (LSH)

Note

In Computer Vision, SIFT is a feature descriptor
Other feature descriptors:

• GIFT
• HOG ^ffb7e9
• SURF
• GLOH
• LBP
• VLAD