3. Block Diagram for Algorithm Workflow
Generating an intermediate frame
Image IS Image I1
Fs → F warp
Feature Spec Feature
Fs Spec F
Morph
Color interpolate
Image
Image I2 Image IT
FT → F warp
Feature Feature
Spec F Spec FT
4. 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
7. The Math (contd):
weighting factor for combining transformations of multiple line segment pairs
b
Weighting factor for combining displacements: length p
Weight
a dist
8. 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')
10. 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