60 lines
1.7 KiB
Groff
60 lines
1.7 KiB
Groff
.TH IM_XYZ2disp 3 "2 Decemder 1992"
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.SH NAME
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im_LabQ2Lab, im_Lab2LabQ, im_LabQ2LabS, im_LabS2LabQ, im_Lab2LabS, im_LabS2Lab \- pack and unpack LABPACK images.
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_LabQ2Lab(in, out)
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.br
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IMAGE *in, *out;
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int im_Lab2LabQ(in, out)
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.br
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IMAGE *in, *out;
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int im_Lab2LabS(in, out)
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.br
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IMAGE *in, *out;
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int im_LabS2LabQ(in, out)
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.br
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IMAGE *in, *out;
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int im_LabS2Lab(in, out)
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.br
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IMAGE *in, *out;
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int im_LabQ2LabS(in, out)
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.br
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IMAGE *in, *out;
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.SH DESCRIPTION
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These functions pack and unpack LAB images.
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LabQ is Lab packed in to 4 unsigned chars, with the Coding field set to
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LABPACK. It counts as a coded type, since most operations will not give the
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correct result on an image of this type. This is the MARC image type. Bits
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are allocated as 10 for L and 11 for each of a and b. The first three bytes
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contain the 8 most significant bits of Lab respectively, the final byte has
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2/3/3 bits (MSB on left) of Lab respectively.
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im_LabQ2Lab() and im_Lab2LabQ() convert LABPACK images to three band float
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images, scaled to look sensible to humans. This is the most convenient LAB
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format for development work, but is rather slow.
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im_LabQ2LabS() and im_LabS2LabQ() convert LABPACK to and from three band
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signed short images. L is shifted and masked to be in the range [0,32767], a
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and b are shifted and masked to lie in [-32768,32767]. This is the best
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computational LAB format, combining precision and speed. Programs such as
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conv(1X) and similarity(1X), which can operate directly on LABPACK images,
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unpack to LabS for computation.
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.SH RETURN VALUE
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The functions return 0 on success and -1 on error.
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.SH SEE ALSO
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im_col_XYZ2rgb(3), im_dE_fromdisp(3), im_XYZ2disp(3).
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.SH COPYRIGHT
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National Gallery, 1990 - 1993
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.SH AUTHOR
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J. Cupitt \- 21/7/93
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