<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html > <head><title>Colour</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="generator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"> <meta name="originator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"> <!-- 3,html --> <meta name="src" content="nipguide.tex"> <meta name="date" content="2010-06-30 13:34:00"> <link rel="stylesheet" type="text/css" href="nipguide.css"> </head><body > <!--l. 29--><div class="crosslinks"><p class="noindent">[<a href="nipguidese15.html" >next</a>] [<a href="#tailnipguidese14.html">tail</a>] [<a href="nipguidech5.html#nipguidese14.html" >up</a>] </p></div> <h3 class="sectionHead"><span class="titlemark">5.1 </span> <a id="x23-450005.1"></a>Colour</h3> <!--l. 30--><p class="noindent" ><a name="nip_label_sec:menu-colour"></a> <!--l. 32--><p class="indent" > This menu groups operations on colorimetric images and patches of colour. A colour patch is three float numbers plus a tag saying how those number should be interpreted as colour (for example, as a colour in CIE LAB colourspace). You can drag and drop between colour patches, and into and from the inkwell in an image paint window. Double-left-click on a colour patch to open a colour select dialog. <!--l. 39--><p class="indent" > <span class="pcrr7t-">nip2 </span>has 9 main types of colorimetric image, see Table <a href="#x23-450011">5.1<!--tex4ht:ref: tb:colour --></a>. All these types are D65 (that is, daylight) absolute colorimetric. When it displays an image, <span class="pcrr7t-">nip2</span> uses the <span class="pcrr7t-">Type </span>field in the image header as a hint on how to transform the numbers in the image into RGB for the display. The current <span class="pcrr7t-">Type </span>is displayed at the end of the caption line below an image thumbnail. <!--l. 46--><p class="indent" > The <span class="pcrr7t-">Mono</span>, <span class="pcrr7t-">GREY16 </span>and <span class="pcrr7t-">RGB16 </span>types are not really calibrated themselves: they are usually whatever you get by loading an image from a file. You’ll usually need an extra step, such as applying an embedded ICC profile, before you get accurate colour. <!--l. 52--><p class="indent" > <a id="x23-450011"></a><hr class="float"><div class="float" > <div class="center" > <!--l. 52--><p class="noindent" > <div class="tabular"> <table id="TBL-2" class="tabular" cellspacing="0" cellpadding="0" rules="groups" ><colgroup id="TBL-2-1g"><col id="TBL-2-1"></colgroup><colgroup id="TBL-2-2g"><col id="TBL-2-2"></colgroup><colgroup id="TBL-2-3g"><col id="TBL-2-3"></colgroup><tr class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr style="vertical-align:baseline;" id="TBL-2-1-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-1-1" class="td11">Name </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-1-2" class="td11">Format </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-1-3" class="td11">Notes </td></tr><tr class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr style="vertical-align:baseline;" id="TBL-2-2-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-2-1" class="td11"><span class="pcrr7t-">Mono </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-2-2" class="td11">One band 8 bit </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-2-3" class="td11">Not calibrated</td> </tr><tr style="vertical-align:baseline;" id="TBL-2-3-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-3-1" class="td11"><span class="pcrr7t-">sRGB </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-3-2" class="td11">Three band 8 bit </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-3-3" class="td11">Screen device space for the sRGB standard </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-4-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-4-1" class="td11"><span class="pcrr7t-">GREY16</span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-4-2" class="td11">One band 16 bit </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-4-3" class="td11">Not calibrated </td></tr><tr style="vertical-align:baseline;" id="TBL-2-5-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-5-1" class="td11"><span class="pcrr7t-">RGB16 </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-5-2" class="td11">Three band 16 bit</td><td style="white-space:nowrap; text-align:left;" id="TBL-2-5-3" class="td11">Not calibrated</td> </tr><tr style="vertical-align:baseline;" id="TBL-2-6-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-6-1" class="td11"><span class="pcrr7t-">Lab </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-6-2" class="td11">Three band float </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-6-3" class="td11">The 1976 version of the CIE perceptual colourspace</td> </tr><tr style="vertical-align:baseline;" id="TBL-2-7-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-7-1" class="td11"><span class="pcrr7t-">LabQ </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-7-2" class="td11">Four band 8 bit </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-7-3" class="td11">Like <span class="pcrr7t-">Lab</span>, but represented as 10:11:11 bits </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-8-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-8-1" class="td11"><span class="pcrr7t-">LabS </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-8-2" class="td11">Three band 16 bit</td><td style="white-space:nowrap; text-align:left;" id="TBL-2-8-3" class="td11">Like <span class="pcrr7t-">Lab</span>, but represented as 15:16:16 bits </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-9-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-9-1" class="td11"><span class="pcrr7t-">LCh </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-9-2" class="td11">Three band float </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-9-3" class="td11"><span class="pcrr7t-">Lab</span>, but with polar coordinates </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-10-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-10-1" class="td11"><span class="pcrr7t-">XYZ </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-10-2" class="td11">Three band float </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-10-3" class="td11">The base CIE colourspace </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-11-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-11-1" class="td11"><span class="pcrr7t-">Yxy </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-11-2" class="td11">Three band float </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-11-3" class="td11">Sometimes useful for colour meters </td> </tr><tr style="vertical-align:baseline;" id="TBL-2-12-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-12-1" class="td11"><span class="pcrr7t-">UCS </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-12-2" class="td11">Three band float </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-12-3" class="td11">Highly uniform space from the CMC(l:c) standard </td> </tr><tr class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr style="vertical-align:baseline;" id="TBL-2-13-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-13-1" class="td11"> </td></tr></table></div></div> <br /><div class="caption" ><span class="id">Table 5.1: </span><span class="content"><span class="pcrr7t-">nip2 </span>colourspaces</span></div><!--tex4ht:label?: x23-450011 --> <!--l. 83--><p class="noindent" ><a name="nip_label_tb:colour"></a> </div><hr class="endfloat" /> <dl class="description"><dt class="description"> <span class="pcrb7t-">New</span> </dt><dd class="description">Make a patch of colour, or pick a colour from a slice through CIELAB colourspace. </dd><dt class="description"> <span class="pcrb7t-">Convert To Colour</span> </dt><dd class="description">Convert anything into a Colour object. </dd><dt class="description"> <span class="pcrb7t-">Colourspace</span> </dt><dd class="description">Change the colourspace. The stored numbers change, but the visual appearance should stay the same. </dd><dt class="description"> <span class="pcrb7t-">Tag As</span> </dt><dd class="description">Change the colourspace tag (the <span class="pcrr7t-">Type </span>field in the image header). The stored numbers stay the same, but the visual appearance should change. </dd><dt class="description"> <span class="pcrb7t-">Colour Temperature</span> </dt><dd class="description">Change the colour temperature. <span class="pcrr7t-">Move Whitepoint </span>just adjusts the ratios of X and Z using the CIE standard illuminants. <!--l. 108--><p class="noindent" ><span class="pcrr7t-">D65 to</span> <span class="pcrr7t-">D50 </span>and <span class="pcrr7t-">D50 to D65 </span>transform using either a 3x3 matrix which is numerically minimal in XYZ space with respect to the colours on a Macbeth Color Checker, or via Bradford cone space. The Bradford transform omits the power term. <!--l. 113--><p class="noindent" >The final two items go from XYZ to LAB and back, but with D50 normalisation rather than the default D65. </dd><dt class="description"> <span class="pcrb7t-">ICC</span> </dt><dd class="description">Transform images (not patches of colour) device space to profile connection space (LAB float) and back. <!--l. 120--><p class="noindent" >You need to be careful about colour temperature issues: all printers work with D50, and <span class="pcrr7t-">nip2 </span>is all D65. Use the D65 to D50 interchange items in the <span class="pcrr7t-">Colour Temperature </span>menu to swap back and forth. <!--l. 125--><p class="noindent" >All printers also work with relative colorimetry, and <span class="pcrr7t-">nip2 </span>is generally absolute. Use <span class="pcrr7t-">Absolute</span> <span class="pcrr7t-">to Relative </span>to scale an absolute colorimetric image by a media white point. </dd><dt class="description"> <span class="pcrb7t-">Radiance</span> </dt><dd class="description"><span class="pcrr7t-">nip2 </span>can read and write images written by the Radiance family of programs (usually with the suffix <span class="pcrr7t-">.hdr</span>), commonly used in HDR photrography. <!--l. 134--><p class="noindent" >Images in this format used a packed floating point layout for their pixels. Items in this menu pack and unpack pixels for you. </dd><dt class="description"> <span class="pcrb7t-">Difference</span> </dt><dd class="description">Calculate various colour difference metrics. You can mix patches of colour and colour images. </dd><dt class="description"> <span class="pcrb7t-">Adjust</span> </dt><dd class="description">Change colour in a colorimetric way. <span class="pcrr7t-">Recombination </span>multiplies each pixel in an image through a matrix. <span class="pcrr7t-">Cast</span> displaces the neutral axis in LAB space. <span class="pcrr7t-">HSB </span>lets you adjust an image in LCh colourspace. </dd><dt class="description"> <span class="pcrb7t-">Similar Colour</span> </dt><dd class="description">find pixels in an image with a similar colour to a patch of colour. </dd><dt class="description"> <span class="pcrb7t-">Measure Colour Chart</span> </dt><dd class="description">This takes a trimmed image of a colour chart (a rectangular grid of coloured squares), measures the average pixel value in the centre 50% of each square, and returns a matrix of the measured values. <!--l. 156--><p class="noindent" >Use <span class="pcrr7t-">Make Synthetic Colour Chart </span>to make a colour chart image from a matrix of measurements. </dd><dt class="description"> <span class="pcrb7t-">Plot ab Scatter</span> </dt><dd class="description">draws a 2 dimensional histogram of the distribution of pixel colours in LAB colourspace. </dd></dl> <!--l. 165--><div class="crosslinks"><p class="noindent">[<a href="nipguidese15.html" >next</a>] [<a href="nipguidese14.html" >front</a>] [<a href="nipguidech5.html#nipguidese14.html" >up</a>] </p></div> <!--l. 165--><p class="indent" > <a id="tailnipguidese14.html"></a> </body></html>