45 lines
1.3 KiB
Groff
45 lines
1.3 KiB
Groff
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.TH IM_LAB_MORPH 3 "8 March 2001"
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.SH NAME
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im_lab_morph \- calculate colour differences
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_lab_morph( IMAGE *in, IMAGE *out,
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.br
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DOUBLEMASK *mask,
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.br
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double L_offset, double L_scale,
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.br
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double a_scale, double b_scale )
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.SH DESCRIPTION
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This function tweaks the colour in an LAB image. It's useful for
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making a 'tweaked' image for sending to a colour printer.
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It performs three corrections: first, it straightens the neutral axis (this is
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useful if your printer tends to tint shadows slightly red, for example); it
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moves L* by adding an offset and then multiplying by a scale (useful if your
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printer thinks in relative colorimetry, for example), and finally scales a*
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and b* by a factor (useful if your printer desaturates to avoid gamut
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clipping).
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The neutral axis straightening is specified as a DOUBLEMASK containing L*, a*
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and b* readings taken from a print of a neutral greyscale (one with a* and b*
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zero). For example:
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3 4
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14.23 4.8 -3.95
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18.74 2.76 -2.62
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23.46 1.4 -1.95
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27.53 1.76 -2.01
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This is interpolated to make an a/b offset for each input value of L*. The top
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and tail are interpolated towards [100,0,0] and [0,0,0]. Entries in the mask
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can be in any order.
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.SH RETURN VALUE
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All functions return 0 on success and -1 on error.
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.SH COPYRIGHT
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National Gallery, 2001
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