# Project 1 (Hybrid Images)

- Emanuel Zgraggen (ez), September 24th, 2011

## Introduction

The task given by this assignment is to build hybrid images using a modification of the approach described in the SIGGRAPH 2006 paper by Oliva, Torralba, and Schyns.

## Approach

**Hybrid Images**

The algorithm takes two input images. For each of the images a laplacian pyramid with height *N* is constructed.
The algorithm constructs a new laplacian pyramid by taking the upper *K* levels (high frequencies) of the first pyramid
and the lower *N - K* levels (low frequencies) of the second pyramid. To obtain a hybrid image, this new pyramid gets
collapsed back into a single image.

**Image blending**

Laplacian pyramids can also be used to seamlessly blend images together. The implemented algorithm follows the approach
described in this
paper by Burt and Adelson (Section 3.2).

The general idea is two create two laplacian pyramids *LA* and *LB* from the two input images *A* and *B*, and
a gaussian pyramid *GR* from the binary mask *R*. *R* indicates which pixels to take from which image.
A new laplacian pyramid *LS* is created by applying the following formula at each level of the pyramids:
*LS(i,j) = GR(i,j,)*LA(i,j) + (1-GR(i,j))*LB(i,j)*

To obtain the blended image, we simply need to collapse *LS* back into a single image.

## Results

**Hybrid Images**

**Image blending**