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PYRAMID

Section: C Library Functions (3)
Updated: 16 Mar 1998
Index

NAME

pyramid, pyramidAver2, pyramidRank2, pyramidGauss5,mkPyramidAver2, mkPyramidRank2, mkPyramidGauss5 -create a pyramidal raster data structure

SYNTAX

#include <xite/pyramid.h>

int pyramidAver2( IBAND b1, IBAND b2 );

int pyramidRank2( IBAND b1, IBAND b2,
int rank );

int pyramidGauss5( IBAND b1, IBAND b2,
ISS_BAND conv );

int mkPyramidAver2( IBAND b, IMAGE* i, int n );

int mkPyramidRank2( IBAND b, IMAGE* i,
int rank, int n );

int mkPyramidGauss5( IBAND b, IMAGE* i,
ISS_BAND conv, int n );

DESCRIPTION

pyramidAver2performs a 2 by 2 average of pixels inb1and places the result in b2.The 2 by 2 windowis then moved two positions, and the process isrepeated over the whole band. b2should thus be halfthe size of b1vertically as well as horizontally.If this is not the case, only pixels occurring inb2,and with four "subpixels" in b1,are handled.The final division by four will always truncate.

pyramidRank2sorts the four pixel values in a 2 by 2window in b1,looks for the ranksorted sequence, and puts this single value intob2.The 2 by 2 window is then moved two positions,and the process is repeated over the whole band.b2should thus be half the size of b1verticallyas well as horizontally. If this is not the case,only pixels occurring in b2,and with four"subpixels" in b1,are handled.

pyramidGauss5performs a 5 by 5 gaussian filteringof pixels in b1with the filter convand subsampelsthe image by 2. The result is placed in b2.b2shouldthus be half the size of b1vertically as well ashorizontally.

mkPyramidAver2creates a pyramid data structure with nlevels from the input band band returns the result as theoutput image i.The bottom layer will have the same size asthe input band rounded down to nearest even, and each layerupwards the pyramid will have half the size of the previous(integer division by 2). The routine uses pyramidAver2repeatedly. With nequal to zero, use the maximum numberof levels.

mkPyramideRank2creates a pyramid data structure with nlevels from the input band band returns the result as theoutput image i.The bottom layer will have the same size asthe input band rounded down to nearest even, and ach layerupwards the pyramid will have half the size of the previous(integer division by 2). From each 2 by 2 window in one layer,the smallest (rank=1), second smallest (rank=2), secondlargest (rank=3) or largest (rank=4) pixel value will beinserted in the layer above. The rankparameter should thusbe in 1..4. The routine uses pyramidRank2 repeatedly. With nequal to zero, use the maximum number of levels.

mkPyramidGauss5creates a pyramid data structure with nlevels from the input band band returns the result as theoutput image i.The bottom layer will have the same size asthe input band rounded down to nearest even, and each layerupwards the pyramid will have half the size of the previous(integer division by 2). The routine uses pyramidGauss5repeatedly. With nequal to zero, use the maximum number oflevels.

RESTRICTIONS

Input and output pixel types must be unsigned byte.

RETURN VALUE

0 => ok
1 => bad pixel type b1
2 => bad pixel type b2
3 => bad rank value (outside 1..4)

AUTHOR

Tor Lřnnestad, BLAB, ifi, UiO.

REVISED

Helene Schulerud, BLAB, ifi, UiO.

ID

$Id: pyramid.c,v 1.30 1997/06/19 08:40:26 svein Exp $

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