1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 6.1, http://www.gnu.org/software/texinfo/ -->
<head>
<title>GNU Octave: Color Conversion</title>
<meta name="description" content="GNU Octave: Color Conversion">
<meta name="keywords" content="GNU Octave: Color Conversion">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Image-Processing.html#Image-Processing" rel="up" title="Image Processing">
<link href="Audio-Processing.html#Audio-Processing" rel="next" title="Audio Processing">
<link href="Plotting-on-top-of-Images.html#Plotting-on-top-of-Images" rel="prev" title="Plotting on top of Images">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>
</head>
<body lang="en">
<a name="Color-Conversion"></a>
<div class="header">
<p>
Previous: <a href="Plotting-on-top-of-Images.html#Plotting-on-top-of-Images" accesskey="p" rel="prev">Plotting on top of Images</a>, Up: <a href="Image-Processing.html#Image-Processing" accesskey="u" rel="up">Image Processing</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Color-Conversion-1"></a>
<h3 class="section">32.5 Color Conversion</h3>
<p>Octave supports conversion from the RGB color system to NTSC and HSV
and vice versa.
</p>
<a name="XREFrgb2hsv"></a><dl>
<dt><a name="index-rgb2hsv"></a>Function File: <em><var>hsv_map</var> =</em> <strong>rgb2hsv</strong> <em>(<var>rgb</var>)</em></dt>
<dt><a name="index-rgb2hsv-1"></a>Function File: <em><var>hsv_map</var> =</em> <strong>rgb2hsv</strong> <em>(<var>rgb</var>)</em></dt>
<dd><p>Transform a colormap or image from red-green-blue (RGB) space to
hue-saturation-value (HSV) space.
</p>
<p>A color in the RGB space consists of red, green, and blue intensities.
</p>
<p>A color in HSV space is represented by hue, saturation, and value
(brightness) levels. Value gives the amount of light in the color. Hue
describes the dominant wavelength. Saturation is the amount of hue mixed
into the color.
</p>
<p><strong>See also:</strong> <a href="#XREFhsv2rgb">hsv2rgb</a>, <a href="Representing-Images.html#XREFrgb2ind">rgb2ind</a>, <a href="#XREFrgb2ntsc">rgb2ntsc</a>.
</p></dd></dl>
<a name="XREFhsv2rgb"></a><dl>
<dt><a name="index-hsv2rgb"></a>Function File: <em><var>rgb_map</var> =</em> <strong>hsv2rgb</strong> <em>(<var>hsv_map</var>)</em></dt>
<dt><a name="index-hsv2rgb-1"></a>Function File: <em><var>rgb_img</var> =</em> <strong>hsv2rgb</strong> <em>(<var>hsv_img</var>)</em></dt>
<dd><p>Transform a colormap or image from hue-saturation-value (HSV) space to
red-green-blue (RGB) space.
</p>
<p>A color in HSV space is represented by hue, saturation and value
(brightness) levels. Value gives the amount of light in the color. Hue
describes the dominant wavelength. Saturation is the amount of hue mixed
into the color.
</p>
<p>A color in the RGB space consists of red, green, and blue intensities.
</p>
<p><strong>See also:</strong> <a href="#XREFrgb2hsv">rgb2hsv</a>, <a href="Representing-Images.html#XREFind2rgb">ind2rgb</a>, <a href="#XREFntsc2rgb">ntsc2rgb</a>.
</p></dd></dl>
<a name="XREFrgb2ntsc"></a><dl>
<dt><a name="index-rgb2ntsc"></a>Function File: <em><var>yiq_map</var> =</em> <strong>rgb2ntsc</strong> <em>(<var>rgb_map</var>)</em></dt>
<dt><a name="index-rgb2ntsc-1"></a>Function File: <em><var>yiq_img</var> =</em> <strong>rgb2ntsc</strong> <em>(<var>rgb_img</var>)</em></dt>
<dd><p>Transform a colormap or image from red-green-blue (RGB) color space to
luminance-chrominance (NTSC) space. The input may be of class uint8,
uint16, single, or double. The output is of class double.
</p>
<p>Implementation Note:
The reference matrix for the transformation is
</p>
<div class="example">
<pre class="example">/Y\ 0.299 0.587 0.114 /R\
|I| = 0.596 -0.274 -0.322 |G|
\Q/ 0.211 -0.523 0.312 \B/
</pre></div>
<p>as documented in <a href="http://en.wikipedia.org/wiki/YIQ">http://en.wikipedia.org/wiki/YIQ</a> and truncated to 3
significant figures. Note: The FCC version of NTSC uses only 2 significant
digits and is slightly different.
</p>
<p><strong>See also:</strong> <a href="#XREFntsc2rgb">ntsc2rgb</a>, <a href="#XREFrgb2hsv">rgb2hsv</a>, <a href="Representing-Images.html#XREFrgb2ind">rgb2ind</a>.
</p></dd></dl>
<a name="XREFntsc2rgb"></a><dl>
<dt><a name="index-ntsc2rgb"></a>Function File: <em><var>rgb_map</var> =</em> <strong>ntsc2rgb</strong> <em>(<var>yiq_map</var>)</em></dt>
<dt><a name="index-ntsc2rgb-1"></a>Function File: <em><var>rgb_img</var> =</em> <strong>ntsc2rgb</strong> <em>(<var>yiq_img</var>)</em></dt>
<dd><p>Transform a colormap or image from luminance-chrominance (NTSC) space to
red-green-blue (RGB) color space.
</p>
<p>Implementation Note:
The conversion matrix is chosen to be the inverse of the matrix used for
rgb2ntsc such that
</p>
<div class="example">
<pre class="example">x == ntsc2rgb (rgb2ntsc (x))
</pre></div>
<p><small>MATLAB</small> uses a slightly different matrix where rounding means the
equality above does not hold.
</p>
<p><strong>See also:</strong> <a href="#XREFrgb2ntsc">rgb2ntsc</a>, <a href="#XREFhsv2rgb">hsv2rgb</a>, <a href="Representing-Images.html#XREFind2rgb">ind2rgb</a>.
</p></dd></dl>
<hr>
<div class="header">
<p>
Previous: <a href="Plotting-on-top-of-Images.html#Plotting-on-top-of-Images" accesskey="p" rel="prev">Plotting on top of Images</a>, Up: <a href="Image-Processing.html#Image-Processing" accesskey="u" rel="up">Image Processing</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
