1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE sect2 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
3                       "http://www.docbook.org/xml/4.3/docbookx.dtd">
4<!-- section history:
5  2008-01-18 lexa: further enhancements to filter description for en, de
6  2007-12-27 lexa: reviewed for color management enhancements
7  2007-05-22 Added Spanish translation by AntI
8  2007-03-18 ude: Re-arranged color proof options
9  2005-12-21 julien: Created en;fr; the "profile" section needs more information
10-->
11<sect2 id="gimp-display-filter-dialog">
12  <title>Display Filters</title>
13
14  <indexterm>
15    <primary>Color</primary>
16    <secondary>Color display</secondary>
17  </indexterm>
18  <para>
19    This command shows a dialog window when executed. This window can be used
20    to manage the display filters and their options. Display filters are not
21    to be confused with the filters in the <guimenu>filters</guimenu>-menu.
22    Display filters do not alter the image data, but only one display of it.
23    You can imagine display filters like big panes before your screen. They
24    change your perception of the image. This can be useful for things like
25    soft proofing prints, controlling the color management but also simulation
26    of color deficient vision.
27  </para>
28
29  <sect3>
30    <title>Activating the Command</title>
31      <para>
32        You can access this command from the image menubar through
33        <menuchoice>
34          <guimenu>View</guimenu>
35          <guimenuitem>Display Filters…</guimenuitem>
36        </menuchoice>.
37      </para>
38  </sect3>
39
40  <sect3>
41    <title>Description of the <quote>Display Filters</quote> Dialog</title>
42    <figure>
43      <title>
44        The <quote>Color Display Filters</quote> dialog
45      </title>
46      <mediaobject>
47        <imageobject>
48          <imagedata format="PNG"
49            fileref="images/menus/view/display-filters.png"/>
50        </imageobject>
51      </mediaobject>
52    </figure>
53    <para>
54      This dialog has two small selectboxes. The left selectbox displays the
55      <guilabel>Available Filters</guilabel>. You can move a filter to the
56      right selectbox by selecting it and clicking on the
57      <guibutton>right arrow</guibutton> button. The
58      <guilabel>Active Filters</guilabel> window on the right displays
59      filters you have chosen and which will be applied if the adjacent box
60      is checked. You can move filters from the right selectbox to the left
61      selectbox by using the <guibutton>left arrow</guibutton> button. If you
62      select a filter by clicking on its name, its options are displayed
63      below the two selectboxes, in the
64      <guilabel>Configure Selected Filter</guilabel> area.
65    </para>
66    <itemizedlist>
67      <listitem>
68        <para>
69          <phrase>Simulation of deficient vision</phrase>
70          (<xref linkend="gimp-deficient-vision"/>;
71          <xref linkend="gimp-contrast-dialog"/>)
72        </para>
73      </listitem>
74      <listitem>
75        <para>
76          <phrase>Digital photography helper</phrase>
77          (<xref linkend="gimp-display-filter-clip-warning"/>)
78        </para>
79      </listitem>
80      <listitem>
81        <para>
82          <phrase>Others</phrase> (<xref linkend="gimp-gamma-dialog"/>)
83        </para>
84      </listitem>
85    </itemizedlist>
86  </sect3>
87
88  <sect3 id="gimp-deficient-vision">
89    <title>Color Deficient Vision</title>
90    <indexterm>
91      <primary>Color</primary>
92      <secondary>Deficient vision</secondary>
93    </indexterm>
94    <para>
95      The images you create, we hope, will be seen by many people on many
96      different systems. The image which looks so wonderful on your screen may
97      look somewhat different to people with sight deficiencies or on a screen
98      with different settings from yours. Some information might not even be
99      visible.
100    </para>
101    <figure>
102      <title>
103        Description of the <quote>Color Deficient Vision</quote> dialog
104      </title>
105      <mediaobject>
106        <imageobject>
107          <imagedata format="PNG"
108            fileref="images/menus/view/display-filters/color-deficient-vision.png"/>
109        </imageobject>
110      </mediaobject>
111    </figure>
112
113    <sect4>
114      <title>Options</title>
115      <variablelist>
116        <varlistentry>
117          <term>Color Deficiency Type</term>
118          <listitem>
119            <para>
120              In this drop-down menu you can select from among:
121            </para>
122            <variablelist>
123              <varlistentry>
124                <term>
125                  Protanopia<footnote>
126                    <para>
127                      Greek:
128                      <foreignphrase>proto</foreignphrase>: first (color in
129                      the <link linkend="glossary-colormodel">RGB Color
130                      System</link>):
131                      <foreignphrase>an</foreignphrase>: negation;
132                      <foreignphrase>op</foreignphrase>: eye, vision.
133                    </para>
134                  </footnote> (insensitivity to red)
135                </term>
136                <listitem>
137                  <para>
138                    Protanopia is a visual deficiency of the color red. It's
139                    the well-known daltonism (red-green color blindness).
140                    Daltonism occurs fairly frequently in the population.
141                  </para>
142                  <para>
143                    Protanopia is actually more complex than this; a person
144                    with this problem cannot see either red or green, although
145                    he is still sensitive to yellow and blue. In addition, he
146                    has a loss of luminance perception and the hues shift
147                    toward the short wavelengths.
148                  </para>
149                </listitem>
150              </varlistentry>
151              <varlistentry>
152                <term>Deuteranopia (insensivity to green)</term>
153                <listitem>
154                  <para>
155                    With deuteranopia, the person has a deficiency in green
156                    vision. Deuteranopia is actually like protanopia, because
157                    the person has a loss of red and green perception, but he
158                    has no luminance loss or hue shift.
159                  </para>
160                </listitem>
161              </varlistentry>
162              <varlistentry>
163                <term>Tritanopia (insensitivity to blue)</term>
164                <listitem>
165                  <para>
166                    With tritanopia, the person is deficient in blue and
167                    yellow perception, although he is still sensitive to red
168                    and green. He lacks some perception of luminance, and the
169                    hues shift toward the long wavelengths.
170                  </para>
171                </listitem>
172              </varlistentry>
173            </variablelist>
174          </listitem>
175        </varlistentry>
176      </variablelist>
177    </sect4>
178
179    <sect4>
180      <title>Examples</title>
181      <figure>
182        <title>Example of protanopia</title>
183        <mediaobject>
184          <imageobject>
185            <imagedata format="PNG"
186              fileref="images/menus/view/display-filters/protanopia-normal.png"/>
187          </imageobject>
188          <caption>
189            <para>Original image</para>
190          </caption>
191        </mediaobject>
192        <mediaobject>
193          <imageobject>
194            <imagedata format="PNG"
195              fileref="images/menus/view/display-filters/protanopia-filtered.png"/>
196          </imageobject>
197          <caption>
198            <!--
199              As you can see, a red-blind person cannot see the red (255,0,0)
200              text on a black (0,0,0) background. You have to change the text
201              color. Daltonism occurs fairly frequently in the population.
202            -->
203            <para>
204              A red-blind person cannot see the red (255,0,0) text on a black
205              (0,0,0) background.
206            </para>
207          </caption>
208        </mediaobject>
209      </figure>
210      <figure>
211        <title>
212          Examples of the three types of vision deficiencies in one image
213        </title>
214        <mediaobject>
215          <imageobject>
216            <imagedata format="PNG"
217              fileref="images/menus/view/display-filters/sight-defects_normal-view.png"/>
218          </imageobject>
219          <caption>
220            <para>Normal vision</para>
221          </caption>
222        </mediaobject>
223        <mediaobject>
224          <imageobject>
225            <imagedata format="PNG"
226              fileref="images/menus/view/display-filters/sight-defects_protanopia.png"/>
227          </imageobject>
228          <caption>
229            <para>Protanopia</para>
230          </caption>
231        </mediaobject>
232        <mediaobject>
233          <imageobject>
234            <imagedata format="PNG"
235              fileref="images/menus/view/display-filters/sight-defects_deuteranopia.png"/>
236          </imageobject>
237          <caption>
238            <para>
239              Deuteranopia; in deuteranopia, yellow is shifted toward red.
240            </para>
241          </caption>
242        </mediaobject>
243        <mediaobject>
244          <imageobject>
245            <imagedata format="PNG"
246              fileref="images/menus/view/display-filters/sight-defects_tritanopia.png"/>
247          </imageobject>
248          <caption>
249            <para>
250              Tritanopia; in tritanopia, green is slightly represented in the
251              blue range.
252            </para>
253          </caption>
254        </mediaobject>
255      </figure>
256    </sect4>
257  </sect3>
258
259  <sect3 id="gimp-gamma-dialog">
260    <title>Gamma</title>
261    <indexterm>
262      <primary>Gamma</primary>
263    </indexterm>
264    <para>
265      <figure>
266        <title>The <quote>Gamma</quote> dialog</title>
267        <mediaobject>
268          <imageobject>
269            <imagedata format="PNG"
270              fileref="images/menus/view/display-filters/gamma.png"/>
271          </imageobject>
272        </mediaobject>
273      </figure>
274    </para>
275    <para>
276      The correspondence between electrical intensity and color brightness
277      is not exact and it depends upon the device (the camera, the scanner,
278      the monitor, etc.). <quote>Gamma</quote> is a coefficient used to
279      correct this correspondence. Your image must be visible in both dark
280      and bright areas, even if it is displayed on a monitor with too much
281      luminence or not enough. The <quote>Gamma</quote> Display Filter
282      allows you to get an idea of the appearance of your image under these
283      conditions.
284    </para>
285    <tip>
286      <para>
287        In case you want not only to change the gamma of the current display,
288        but the change the gamma within the image itself, you can find a
289        description in <xref linkend="gimp-tool-levels"/>.
290      </para>
291    </tip>
292  </sect3>
293
294  <sect3 id="gimp-contrast-dialog">
295    <title>Contrast</title>
296    <indexterm>
297      <primary>Contrast</primary>
298    </indexterm>
299    <para>
300      <figure>
301        <title>The <quote>Contrast</quote> dialog</title>
302        <mediaobject>
303          <imageobject>
304            <imagedata format="PNG"
305              fileref="images/menus/view/display-filters/contrast.png"/>
306          </imageobject>
307        </mediaobject>
308      </figure>
309    </para>
310    <para>
311      Here, we are back in the medical domain.
312      <quote>Contrast Sensitivity</quote>
313      is the capacity of the visual system to distinguish slight differences
314      in contrast. Some people with cataracts (which means that the lens has
315      opaque crystals that scatter light over the retina) or retinal disease
316      (for instance, due to diabetes, which destroys the rods and cones) have
317      a deficiency in sensitivity to contrast: for example, they would have
318      difficulties distinguishing spots on a dress.
319    </para>
320    <para>
321      If you are interested in this subject, you can browse the Web for
322      <quote>contrast sensitivity</quote>.
323    </para>
324
325    <sect4>
326      <title>Options</title>
327      <variablelist>
328        <varlistentry>
329          <term>Contrast Cycles</term>
330          <listitem>
331            <para>
332              With the <quote>Contrast</quote>
333              Filter, you can see the image as if you were suffering from
334              cataracts. You may have to increase the contrast of the image so
335              that your grandmother can see it well. In most cases, only very
336              low values of the <guilabel>Contrast Cycles</guilabel>
337              parameter are of interest. Higher values create a side-effect
338              which doesn't interest us here: if you increase the luminosity
339              value above 255, the complementary color appears.
340            </para>
341          </listitem>
342        </varlistentry>
343      </variablelist>
344    </sect4>
345  </sect3>
346
347  <sect3 id="gimp-display-filter-clip-warning">
348    <title>Clip Warning</title>
349    <indexterm>
350      <primary>Clip Warning</primary>
351    </indexterm>
352    <figure>
353      <title>The <quote>Clip Warning</quote> dialog</title>
354      <mediaobject>
355        <imageobject>
356          <imagedata format="PNG"
357            fileref="images/menus/view/display-filters/clip-warning.png"/>
358        </imageobject>
359      </mediaobject>
360    </figure>
361    <para>
362      This filter allows to visualize underexposed and overexposed areas of
363      a photo with user-configurable colors. For now, it’s mostly geared
364      towards images where colors are stored with floating point precision.
365      You will mostly benefit from this, if you work on 16-/32-bit per channel
366      float images such as EXR and TIFF.
367    </para>
368
369    <sect4>
370      <title>Options</title>
371      <variablelist>
372        <varlistentry>
373          <term>Show shadows</term>
374          <listitem>
375            <para>
376              Enable visualization for underexposed pixels (less than 0 in
377              32-bit float mode).
378            </para>
379          </listitem>
380        </varlistentry>
381        <varlistentry>
382          <term>Shadows color</term>
383          <listitem>
384            <para>
385              User-configurable color that will be used to fill underexposed
386              pixels.
387            </para>
388          </listitem>
389        </varlistentry>
390        <varlistentry>
391          <term>Show highlights</term>
392          <listitem>
393            <para>
394              Enable visualization for overexposed pixels (more than 1 in
395              32-bit float mode).
396            </para>
397          </listitem>
398        </varlistentry>
399        <varlistentry>
400          <term>Highlights color</term>
401          <listitem>
402            <para>
403              User-configurable color that will be used to fill overexposed
404              pixels.
405            </para>
406          </listitem>
407        </varlistentry>
408        <varlistentry>
409          <term>Show bogus</term>
410          <listitem>
411            <para>
412              Enable visualization for not-a-number (NaN) pixels, only visible
413              when there is a division by zero error and suchlike.
414            </para>
415          </listitem>
416        </varlistentry>
417        <varlistentry>
418          <term>Bogus color</term>
419          <listitem>
420            <para>
421              User-configurable color that will be used to fill NaN     pixels.
422            </para>
423          </listitem>
424        </varlistentry>
425        <varlistentry>
426          <term>Include alpha component</term>
427          <listitem>
428            <para>
429              When enabled, include the alpha component in the warning.
430            </para>
431          </listitem>
432        </varlistentry>
433        <varlistentry>
434          <term>Include transparent pixels</term>
435          <listitem>
436            <para>
437              When enabled, include fully transparent pixels in the warning.
438            </para>
439          </listitem>
440        </varlistentry>
441      </variablelist>
442    </sect4>
443  </sect3>
444</sect2>
445