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Movie creation from a mosaic of images

Emilio Casanova
Departement of Microengineering

Student semester project, June 2001
Introduction

The presentation of static images in the form of a video offers interesting possibilities like focusing the attention of public on a detail or following a didactic course on the images. In one preceding project various functions were developed making it possible to create an big image starting from a series of small images , this using techniques of mosaicing. For this application we require that the images have a recovery two to two significant. In this work we describe on the one hand, a series of routines allowing to improve creation of the mosaic. In addition we implemented a program which creates a video by simulating the trajectory of a virtual camera in the mosaic. These various stages have summers carried out using interpolation tools of the Biomedical Imaging Group (BIG).
Mosaic of 18 images of a young mouse cell.
Mosaic size : 3329 x 1114 px
Images size : 768 x 576 px
Quality : maximum
Time taken : 500 sec
Click on the image to enlarge (232 Ko)
Movie construction

The interpolation of the trajectory and the zoom by cubic B-splines gave us satisfactory results. In what relates to the tools for interpolation for the calculation of the images, we noticed the following points :
  • The first approach consisting in using IDL routines allows a fast calculation of the images but causes effects of pixelisation significant with large zoom (Nearest-neighbor interpolation). We will thus use this method in order to make a video test quickly.
Click on the image for seeing the movie.
  • In the second approach we used the routine Affine (of the Biomedical Imaging Group) allowing to have results of better quality ( B-spline cubic interpolation) but requiring a more significant calculating time (surroundings 12 times more). It is this method which we will use to create the final movie.
Click on the image for seeing the movie.
Conclusions

The objective of this project was initially to improve creation of a mosaic of images. A user interface, making it possible to visualize and align the images, as well as an algorithm allowing to choose automatically the pairs of images to be aligned were thus implemented. The mosaic creation is more robust. Some alignment problems of the images in rotation were solved.
It appears interesting to us to build color mosaics for thus benefitting from various colourings (fluorescence) possible in optical microscopy.
With regard to the video creation, we have at disposal a complete interface. Thanks to this one we can load an image, define a course and its characteristics (zoom...), define a video size and build a film. This approach has a great potential in the exploitation of big images.
 
EPFL Swiss Federal Institute of Technology Lausanne
BIG Biomedical Imaging Group
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Last updated : 7 November 2001