CS U540 Computer Graphics. Prof. Harriet Fell Spring 2007 Lecture 34 – April 4, 2007. Today’s Topics. Morphing Two Towers > Disk 4 > Visual Effects > Weka Digital. Morphing History. Morphing is turning one image into another through a seamless transition.
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Prof. Harriet Fell
Lecture 34 – April 4, 2007
Visual Effects > Weka Digital
There are two ways to warp an image:
(x, y )
(x, y )
(1-t)Image1 + (t)Image2
T = .5
SPHarriet & MandrillMatching Eyes
Match the endpoints of a line in the source with the endpoints of a line in the destination.
X=(x ,y )
vLine Pair Map
The line pair maptakes the source image to an image the same size as the destinations and take the line segment in the source to the line segment in the destination.
DPFinding u and v
u is the proportion of the distance from DP to DQ.
v is the distance to travel in the perpendicular direction.
% Scale image Source to one size DW, DH with line pair mapping
function Dest = forwardMap(Source, DW, DH, SP, SQ, DP, DQ);
% Source is the source image
% DW is the destination width
% DH is the destination height
% SP, SQ are endpoints of a line segment in the Source [y, x]
% DP, DQ are endpoints of a line segment in the Dest [y, x]
Dest = zeros(DH, DW,3); % rows x columns x RGB
SW = length(Source(1,:,1)); % source width
SH = length(Source(:,1,1)); % source height
for y= 1:DH
for x = 1:DW
u = ([x,y]-DP)*(DQ-DP)'/((DQ-DP)*(DQ-DP)');
v = ([x,y]-DP)*perp(DQ-DP)'/norm(DQ-DP);
SourcePoint = SP+u*(SQ-SP) + v*perp(SQ-SP)/norm(SQ-SP);
SourcePoint = max([1,1],min([SW,SH], SourcePoint));
% display the image
title('line pair map');
function Vperp = perp(V)
Vperp = [V(2), - V(1)];
Find Xi' for the ith pair of lines.
Di = Xi' – X
Use a weighted average of the Di.
Weight is determined by the distance from X to the line.
length = length of the line
dist is the distance from the pixel to the line
a, b, and p are used to change the relative effect of the lines.
Add average displacement to X to determine X‘.