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2.11 Mosaicing

See figure 2.13.

These functions are useful for joining many small images together to make one large image. They can cope with unstable contrast, and arbitary sub-image layout, but will not do any geometric correction. The mosaicing functions can be grouped into layers:

The lowest level functions are im_correl(). and im_affine(). im_correl() searches a large image for a small sub-image, returning the position of the best sub-image match. im_affine() performs a general affine transform on an image: that is, any transform in which parallel lines remain parallel.

Next, im_lrmerge() and im_tbmerge() blend two images together left-right or up-down.

Next up are im_lrmosaic() and im_tbmosaic(). These use the two low-level merge operations to join two images given just an approximate overlap as a start point. Optional extra parameters let you do 'balancing' too: if your images have come from a source where there is no precise control over the exposure (for example, images from a tube camera, or a set of images scanned from photographic sources), im_lrmosaic() and im_tbmosaic() will adjust the contrast of the left image to match the right, the right to the left, or both to some middle value.

The functions im_lrmosaic1() and im_tbmosaic1() are first-order analogues of the basic mosaic functions: they take two tie-points and use them to rotate and scale the right-hand or bottom image before starting to join.

Finally, im_global_balance() can be used to re-balance a mosaic which has been assembled with these functions. It will generally do a better job than the low-level balancer built into im_lrmosaic() and im_tbmosaic(). See the man page. im_remosaic() uses the same techniques, but will reassemble the image from a different set of source images.

Figure 2.13: Mosaic functions
\begin{figure}\begin{quote}
\begin{verbatim}example% vips -help mosaicing
func...
...st-order top-bottom mosaic of ref and sec\end{verbatim}
\end{quote}
\end{figure}


next up previous contents
Next: 2.12 Other Up: 2. VIPS packages Previous: 2.10 Morphology   Contents
John Cupitt 2004-11-02