I have done an implementation of this paper from CG&A for image reconstruction.

Original and a greyscale from CIE luminance

8x magnification - greyscale

8x scale using gimp

DDT method (8 passes using yms optimisation)

8x magnification - colour

8x scale using gimp

DDT method (8 passes using yms optimisation)

DDT method (3 passes using yms optimisation)

Photo from a recent shuttle mission

original photo

zoomed section original

4x magnification using gimp

DDT method (8 passes using yms optimisation

A simple example

Original

My implementation

Gimp version

Another edge-directed algorithm on the same image

[ICO]NameLast modifiedSizeDescription

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[IMG]costfunc.png 2002-05-30 21:10 3.4K 
[IMG]flow.png 2002-06-09 21:35 53K 
[IMG]flowerg-gimp.png 2002-06-25 21:53 50K 
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[   ]imagefilt-rob.tar.gz 2003-01-06 13:57 37K 
[IMG]lisa-gimp8.png 2002-06-08 14:51 310K 
[IMG]lisa-gimp8c.png 2002-06-08 14:32 710K 
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[IMG]s110e5004.jpg 2002-06-08 15:52 1.4M 
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[IMG]thigh.png 2002-06-12 11:39 306K 
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[TXT]truck-distance-8pass..>2002-06-11 07:13 681  
[TXT]truck-distance-8pass..>2002-06-11 07:13 340  
[TXT]truck-yms-8pass.txt 2002-06-11 07:13 340  
[IMG]truck.png 2002-06-11 07:30 224K