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$ \bigcirc$Name

ll_sharp Sharpen an image (select some of the parallel level lines)

$ \bigcirc$Command Synopsis

ll_sharp [-p percent_area] image_in image_out

-p percent_area : % area change to glue parent and child (default: 20)

image_in : Input fimage

image_out : Output fimage

$ \bigcirc$Function Summary

void ll_sharp (pPercentIncreaseArea , pFloatImageInput , pFloatImageOutput )

float *pPercentIncreaseArea ;

Fimage pFloatImageInput , pFloatImageOutput ;

$ \bigcirc$Description

This module is a kind of shock filter based on the FLST (see modules flst and flst_reconstruct). It is a non-uniform quantization of an image based on shapes. One shape S and its child C are in the same gradation iff:

  1. C is the only child of S;
  2. C and S have the same type;
  3. the areas of C and S do not differ more than a certain factor.
  4. C is not an elementary shape, that is all the children of C (if there are some) are of the same type of C.
An elementary shape (ie having a child with a different type) is considered to be a gradation by itself. These shapes must not be removed to keep consistency between the tree and the image it represents (see module flst). It is not difficult to see that this relation induces a partition of the family of shapes, each class of the partition is then called a gradation. The representative shape of the gradation is the shape of the gradation with smallest L2/A where A is the area and L is the length of its boundary. This gray value of this shape is set to the mean of the gray value of the image inside the gradation. The definition of a gradation depends on a factor of increase of area, given by percent_area. When it is close to 0, this parameter isolates each shape as one gradation and when it is large, it gathers the maximum of shapes inside each gradation. This shock filter gives better effects when the grain filter is applied to the image before (see module fgrain). In this case, the number or remaining level lines can be dramatically smaller than in the original image, whereas the structure of the image seems unchanged.

$ \bigcirc$See Also

flst, flst_reconstruct.

$ \bigcirc$Version 1.4

Last Modification date : Mon Jan 28 11:46:12 2002

$ \bigcirc$Author

Pascal Monasse, Frederic Guichard

next up previous contents index
Next: mam Up: Reference Previous: Output   Contents   Index
mw 2004-05-05