digital image morphing through field morphing

Ankur Sakhuja

DIGITAL IMAGE MORPHING THROUGH “FIELD MORPHING”

Example

Block Diagram for Algorithm WorkflowGenerating an intermediate frame

Image IS

Feature Spec Fs

Image I2

Feature Spec F

Fs → F warp

FT → F warp

Image I1

Feature Spec F

Image IT

Feature Spec FT

MorphImage

Color interpolate

Algorithm overview

Basic motivation: specification of feature points as lines – more expressive and intuitive

Line features specified in both source and target images and correspondence established

For every intermediate position in morph sequence, a line feature set is generated by interpolating the two sets

Between source and intermediate line feature sets:- Every pair of line features represents a coordinate transformation

for a point from source to target image – results in some spatial displacement

A weighted sum of displacements due to all line pairs gives net displacement of a point – the total warp function

Warp both source and target images to get two intermediate images

Color interpolate to obtain the morph image Repeat for every position in the sequence to obtain the morph

sequence

The Math: Pixel transformation specified by single pair of line segments

The Math (contd):Pixel transformation specified by two pairs of line segments

The Math (contd):weighting factor for combining transformations of multiple line segment pairs

Weighting factor for combining displacements:bp

dista

lengthWeight

Algorithm Pseudocode

• For each pixel X in the destination• DSUM = (0,0)• weightsum = 0 • For each line Pi Qi• calculate u,v based on Pi Qi• calculate X'i based on u,v and Pi'Qi'• calculate displacement Di = Xi' - Xi for this line• dist = shortest distance from X to Pi Qi • weight = (lengthp / (a + dist))b• DSUM += Di * weight • weightsum += weight • X' = X + DSUM / weightsum• destinationImage(X) = sourceImage(X')

MATLAB Implementation and Results

Reference

1. Beier, T. and Neely, S. 1992. Feature-based image metamorphosis. In Proceedings of the 19th Annual Conference on Computer Graphics and interactive Techniques