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<title>IM_XYZ2disp(3) manual page</title>
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<a href='#toc'>Table of Contents</a><p>
<h2><a name='sect0' href='#toc0'>Name</a></h2>
im_XYZ2disp, im_disp2XYZ, im_Lab2XYZ, im_XYZ2Lab, im_XYZ2Yxy, im_Yxy2XYZ,
im_XYZ2sRGB, im_sRGB2XYZ, im_Lab2LCh, im_LCh2Lab, im_LCh2UCS, im_UCS2LCh
- convert images between various colour spaces
<h2><a name='sect1' href='#toc1'>Synopsis</a></h2>
#include <vips/vips.h>
<p> int im_XYZ2disp(in, out, display) <br>
IMAGE *in, *out; <br>
struct im_col_display *display;
<p> int im_disp2XYZ(in, out, display) <br>
IMAGE *in, *out; <br>
struct im_col_display *display;
<p> int im_Lab2XYZ(in, out) <br>
IMAGE *in, *out;
<p> int im_XYZ2Lab(in, out) <br>
IMAGE *in, *out;
<p> int im_XYZ2Yxy(in, out) <br>
IMAGE *in, *out;
<p> int im_Yxy2XYZ(in, out) <br>
IMAGE *in, *out;
<p> int im_XYZ2sRGB(in, out) <br>
IMAGE *in, *out;
<p> int im_sRGB2XYZ(in, out) <br>
IMAGE *in, *out;
<p> int im_Lab2LCh(in, out) <br>
IMAGE *in, *out;
<p> int im_LCh2Lab(in, out) <br>
IMAGE *in, *out;
<p> int im_LCh2UCS(in, out) <br>
IMAGE *in, *out;
<p> int im_UCS2LCh(in, out) <br>
IMAGE *in, *out;
<p>
<h2><a name='sect2' href='#toc2'>Description</a></h2>
Functions to convert images between the different
colour spaces supported by VIPS: RGB, sRGB, XYZ, Yxy, Lab, LCh and UCS.
RGB and sRGB are three band uchar files. XYZ, Lab, LCh and UCS are three
band float files.
<p> These are the basic conversion routines provided by VIPS.
Other conversions, such as <a href='im_Lab2disp.3.html'>im_Lab2disp(3)</a>
, are built by composing these
functions and are provided as a convenience to the programmer.
<p> The VIPS
colour spaces inter-convert as follows:
<p> +------- sRGB<br>
|<br>
LabQ ----- Lab ----- XYZ ----- RGB<br>
| | |<br>
| | +------- Yxy<br>
| |<br>
| +------- LCh ----- UCS<br>
|<br>
+-------- LabS<br>
<p> The colour spaces are:
<p> LabQ --- This is the principal VIPS colorimetric
storage format. See <a href='im_LabQ2Lab.3.html'>im_LabQ2Lab(3)</a>
for an explanation. You cannot perform
calculations on LabQ images. They are for storage only.
<p> LabS --- This format
represents coordinates in CIE Lab space as 16-bit integers. It is the best
format for computation, being relatively compact, quick, and accurate. Colour
values expressed in this way are hard to visualise. See the page for im_LabQ2LabS().
<p> Lab --- Coordinates in CIE Lab space are represented as float values in the
usual range. This is the easiest format for general work: adding 50 to the
L channel, for example, has the expected result.
<p> XYZ --- CIE XYZ colour space.
<p> Yxy --- CIE Yxy colour space.
<p> RGB --- This format is compatible with the RGB
colour systems used in other packages. If you want to export your image
to a PC, for example, convert your colorimetric image to RGB, then turn
it to TIFF with <a href='vips2TIFF.1.html'>vips2TIFF(1)</a>
. You need to supply a structure which characterises
your display. See the manual page for <a href='im_col_XYZ2rgb.3.html'>im_col_XYZ2rgb(3)</a>
for hints on these
guys.
<p> sRGB --- This is a standard RGB, as defined by:
<p> <a href='http://www.color.org/contrib/sRGB.html'>http://www.color.org/contrib/sRGB.html</a>
<br>
<p> it’s handy for carrying colour information through JPEG compressors, for
example.
<p> LCh --- Like Lab, but the rectangular ab coordinates are replaced
with the polar Ch (Chroma and hue) coordinates. Hue angles are expressed
in degrees.
<p> UCS --- A colour space based on the CMC(1:1) colour difference
measurement. This is a highly uniform colour space, much better than Lab
for expressing small differences. Conversions to and from UCS are extremely
slow.
<p> These conversions set the Type field in the image header to LABQ,
LABS, LAB, XYZ, RGB, sRGB, LCH and UCS respectively. The Type field is for
user information only --- no function reads the Type field to determine its
behaviour. Visualisation programs, such as <a href='ip.1.html'>ip(1)</a>
, use the Type field to
help present the information to the user.
<p> All VIPS colour spaces are based
around D65.
<p> VIPS has functions for finding colour difference images. See
<a href='im_dE_fromLab.3.html'>im_dE_fromLab(3)</a>
.
<p>
<h2><a name='sect3' href='#toc3'>Return Value</a></h2>
The functions return 0 on success and -1 on
error.
<h2><a name='sect4' href='#toc4'>See Also</a></h2>
<a href='im_col_XYZ2rgb.3.html'>im_col_XYZ2rgb(3)</a>
, <a href='im_dE_fromLab.3.html'>im_dE_fromLab(3)</a>
, <a href='im_LabQ2Lab.3.html'>im_LabQ2Lab(3)</a>
, <a href='im_Lab2disp.3.html'>im_Lab2disp(3)</a>
.
<h2><a name='sect5' href='#toc5'>Copyright</a></h2>
National Gallery and Birkbeck College, 1990 - 1993
<h2><a name='sect6' href='#toc6'>Author</a></h2>
K. Martinez
- 2/12/1992 <br>
J. Cupitt - 21/7/93 <p>
<hr><p>
<a name='toc'><b>Table of Contents</b></a><p>
<ul>
<li><a name='toc0' href='#sect0'>Name</a></li>
<li><a name='toc1' href='#sect1'>Synopsis</a></li>
<li><a name='toc2' href='#sect2'>Description</a></li>
<li><a name='toc3' href='#sect3'>Return Value</a></li>
<li><a name='toc4' href='#sect4'>See Also</a></li>
<li><a name='toc5' href='#sect5'>Copyright</a></li>
<li><a name='toc6' href='#sect6'>Author</a></li>
</ul>
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Mandriva
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2010.0
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i586
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media
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files
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