64 lines
1.4 KiB
Groff
64 lines
1.4 KiB
Groff
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.TH IM_MSB 3 "06 May 2006"
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.SH NAME
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im_msb, im_msb_band \- Convert to uchar by discarding bits
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.SH SYNOPSIS
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.nf
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.B #include <vips/vips.h>
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.sp
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.BI "int im_msb( IMAGE " "*in" ", IMAGE " "*out" " );
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.br
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.BI "int im_msb_band( IMAGE " "*in" ", IMAGE " "*out" ", int " "band" " );
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.fi
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.SH DESCRIPTION
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.B im_msb(3)
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converts char, short, or int images (including LABQ coded ones) into unsigned
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char images, very quickly, by discarding the lower order bits. Once scaled to
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char, signed values are converted to unsigned by adding 128.
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.PP
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For a signed short (16 bit) image,
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.PP
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im_msb( in, out );
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.PP
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is equivalent to:
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.PP
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im_lintra( (1.0/256.0), in, 128.0, temp );
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.br
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im_clip2fmt( temp, out, IM_BANDFMT_UCHAR );
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.PP
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but much faster.
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.PP
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For any image which uses the whole range of values for its band format,
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.PP
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im_msb( in, out );
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.PP
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is equivalent to:
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.PP
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im_scale( in, out );
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.PP
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but a great deal faster, and without evaluating the input twice.
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.PP
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.B im_msb_band(3)
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is as
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.BR im_msb(3) ,
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except that all but one of the bands are also discarded.
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.PP
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im_msb_band( in, out, i );
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.PP
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is equivalent to:
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.PP
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im_msb( in, temp );
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.br
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im_extract_bands( temp, out, i, 1 );
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.PP
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but again, faster.
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.SH RETURN VALUE
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The functions returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_lintra(3), im_scale(3), im_clip(3)
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.SH COPYRIGHT
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.br
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Copyright 2006, The Nottingham Trent University.
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.SH AUTHOR
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Tom Vajzovic
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