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 2017-04-01 elle stone: add enable-color-management.xml 6--> 7<sect2 id="gimp-image-enable-color-management"> 8 <title>Enable Color Management</title> 9 10 <indexterm> 11 <primary>Image</primary> 12 <secondary>Color Management</secondary> 13 <tertiary>Enable Color Management</tertiary> 14 </indexterm> 15 <indexterm> 16 <primary>Color Management</primary> 17 <secondary>Enable Color Management</secondary> 18 </indexterm> 19 <indexterm> 20 <primary>Enable Color Management</primary> 21 </indexterm> 22 23 <para> 24 If unchecked, <guimenuitem>Enable Color Management</guimenuitem> 25 assigns a GIMP built-in sRGB color space to your image. 26 </para> 27 28 <para> 29 Also, if you've selected to 30 display the image's assigned ICC color profile on the title or status bar, 31 unchecking Enable Color Management prints 32 the phrase "not color managed" to the title or status bar in place 33 of the previously assigned color profile. 34 </para> 35 36 <note> 37 <para>Enable Color Management is checked by default. It's best to leave 38 this option checked. 39 </para> 40 </note> 41 42 <sect3> 43 <title>Activating the command</title> 44 <para> 45 You can access this command from the image menu bar through 46 <menuchoice> 47 <guimenu>Image</guimenu> 48 <guisubmenu>Color Management</guisubmenu> 49 <guimenuitem>Enable Color Management</guimenuitem> 50 </menuchoice>. 51 </para> 52 </sect3> 53 54 55 <sect3> 56 <title> 57 Use Notes regarding unchecking 58 <guimenuitem>Enable Color Management</guimenuitem> 59 </title> 60 <para> 61 The best possible advice is to <emphasis role="bold">never uncheck <guimenuitem>Enable Color Management</guimenuitem></emphasis>. 62 </para> 63 </sect3> 64<!-- <para> 65 If your image is already in one of GIMP's built-in sRGB color spaces, 66 unchecking Enable Color Management makes no difference whatsoever in your 67 editing results or in the appearance of your image. 68 </para> 69 <para> 70 If your image is not already in one of GIMP's built-in sRGB color 71 spaces, then the only time unchecking Enable Color Management won't change 72 your image's appearance is if the ICC profile assigned to your image has: 73 </para> 74 <orderedlist> 75 <listitem> 76 <para> 77 The same channel encoding as the channel encoding that 78 GIMP happens to be using at the time you uncheck Enable Color Management. 79 </para> 80 </listitem> 81 <listitem> 82 <para> 83 The same chromaticities as the chromaticities of the 84 built-in GIMP sRGB profiles. 85 </para> 86 </listitem> 87 </orderedlist> 88 <para> 89 In the above case unchecking Enable Color Management is the 90 functional equivalent of assigning the built-in sRGB profile to your image, 91 except that simply assigning the built-in sRGB profile to your image 92 doesn't produce a misleading status or title bar message that the image is 93 "not color managed". 94 </para> 95 </sect3>--> 96 97 <sect3> 98 <title> 99 What does GIMP do when 100 <guimenuitem>Enable Color Management</guimenuitem> is unchecked? 101 </title> 102 <para> 103 When you uncheck the option to 104 <guimenuitem>Enable Color Management</guimenuitem>, GIMP does 105 two things: 106 </para> 107 <orderedlist> 108 <listitem> 109 <para> 110 Whatever ICC profile is currently assigned to the image 111 file is at least temporarily stored (pending subsequent editing, 112 Precision, and Color Management actions), but isn't used. 113 And then a built-in GIMP profile is assigned in place of the previously 114 assigned ICC profile: 115 </para> 116 <itemizedlist> 117 <listitem> 118 <para>If the image is at Perceptual gamma (sRGB) precision, 119 the ICC profile "GIMP built-in sRGB" is assigned. 120 </para> 121 </listitem> 122 <listitem> 123 <para> 124 If the image is at Linear light precision, the ICC 125 profile "GIMP built-in Linear sRGB" is assigned. 126 </para> 127 </listitem> 128 </itemizedlist> 129 <para> 130 You can confirm that one of GIMP's built-in sRGB color spaces has 131 been assigned by checking "Image/Image Properties/Color Profile". 132 </para> 133 </listitem> 134 <listitem> 135 <para> 136 If you have set up the title or status bar to show the 137 image's color space, then the title or status bar will display a message 138 that the image is "not color managed". <emphasis>In reality the image is 139 still color managed</emphasis>, but now the image is color managed 140 "as if" it were in one of GIMP's built-in sRGB color spaces instead of 141 whatever color space it's actually in. 142 </para> 143 </listitem> 144 </orderedlist> 145 </sect3> 146 147 <sect3> 148 <title> 149 When <guimenuitem>Enable Color Management</guimenuitem> 150 is unchecked, what happens to the image 151 and the image appearance? 152 </title> 153 <note> 154 <para> 155 Assigning a new profile to an image doesn't change the image's 156 actual channel values. Assigning a new ICC profile only changes the meaning 157 of the channel values, which means the image appearance will change (unless 158 the original and new profile are functionally equivalent). 159 </para> 160 </note> 161 <para> 162 When <guimenuitem>Enable Color Management</guimenuitem> is unchecked, 163 GIMP assigns one of GIMP's 164 built-in sRGB profiles to the image. Assigning a new ICC profile to an image 165 doesn't change the image's channel values, but it does more or less 166 drastically change the image's appearance: 167 </para> 168 <orderedlist> 169 <listitem> 170 <para>If the image was already in one of GIMP's built-in color 171 spaces (or if the assigned ICC profile is a profile that is functionally 172 equivalent to the assigned GIMP built-in sRGB profile) then the image's 173 appearance will not change. 174 </para> 175 </listitem> 176 <listitem> 177 <para> 178 If the image was not already in one of GIMP's built-in 179 color spaces (and is not in a color space that is functionally 180 equivalent to the assigned GIMP built-in sRGB profile), 181 the image's appearance will change more 182 or less drastically depending on three things: 183 </para> 184 <itemizedlist> 185 <listitem> 186 <para> 187 What GIMP Precision channel encoding — 188 Linear light or Perceptual gamma (sRGB) — the image was in 189 before the <guimenuitem>Enable Color Management</guimenuitem> box was unchecked. 190 </para> 191 </listitem> 192 <listitem> 193 <para> 194 How far the image's originally assigned ICC profile's 195 channel encoding ("TRC") is from the GIMP Precision channel encoding. 196 </para> 197 </listitem> 198 <listitem> 199 <para> 200 How far the image's originally assigned ICC profile's 201 Red, Green, and Blue chromaticities are from GIMP's built-in sRGB 202 chromaticities. 203 </para> 204 </listitem> 205 </itemizedlist> 206 </listitem> 207 </orderedlist> 208 </sect3> 209 210 <sect3> 211 <title> 212 Two screenshots showing examples of correct and incorrect image 213 appearances after unchecking 214 <guimenuitem>Enable Color Management</guimenuitem> 215 </title> 216 <para> 217 In both screenshots shown below, the image is color 218 managed: An ICC profile is assigned to the image, and that profile is being 219 used to send the image colors to the screen. 220 </para> 221 <para> 222 But in the second screenshot, after unchecking Enable Color 223 Management, one of GIMP's built-in sRGB profiles has been incorrectly 224 assigned to the image, so the colors look wrong. 225 </para> 226 <para> 227 In screenshot 1 below, the image is already in a GIMP built-in sRGB 228 color space. So unchecking <guimenuitem>Enable Color Management</guimenuitem> 229 makes no difference in the appearance of the image. In this 230 particular case unchecking <guimenuitem>Enable Color Management</guimenuitem> actually makes 231 no difference at all, except that if you've selected to show the 232 image's assigned ICC profile in the title or status bar, then instead 233 of showing the assigned ICC profile, the title or status bar will 234 show the words "not color managed". But in reality the image is still 235 color managed: 236 </para> 237 <mediaobject> 238 <imageobject> 239 <imagedata fileref="images/menus/image/color-management/enable-cm-gimp-built-in-perceptual-srgb-color-space-enabled-disabled.png" format="PNG"/> 240 </imageobject> 241 </mediaobject> 242 243 <para> 244 In screenshot 2 below, the channel encoding of the original profile 245 matches the GIMP channel encoding (both are linear), but the 246 LargeRGB-elle-V4-g10.icc profile chromaticities don't match the GIMP built-in 247 sRGB chromaticities. So after unchecking 248 <guimenuitem>Enable Color Management</guimenuitem>, the tonality 249 is correct but the colors are wrong. The image is still color managed, 250 but it's color managed using the wrong ICC profile: 251 </para> 252 <mediaobject> 253 <imageobject> 254 <imagedata fileref="images/menus/image/color-management/enable-cm-linear-precision-mismatched-chromaticities.png" format="PNG"/> 255 </imageobject> 256 </mediaobject> 257 <caution> 258 <para> 259 If your image's originally assigned ICC profile doesn't have the same 260 channel encoding and chromaticities as the GIMP built-in sRGB profile, and 261 you uncheck and then immediately change your mind 262 and recheck <guimenuitem>Enable Color Management</guimenuitem>, 263 the originally assigned ICC profile 264 will be reassigned to your image and your image channel values will be 265 unchanged. 266 </para> 267 <para> 268 Otherwise, whether or not you can recover the originally 269 assigned ICC profile and correct colors for your image depends on what 270 else you've done between the unchecking and rechecking of 271 <guimenuitem>Enable Color Management</guimenuitem>. 272 </para> 273 <para> 274 Again, the best possible advice is to <emphasis role="bold">never uncheck <guimenuitem>Enable Color Management</guimenuitem></emphasis>. 275 </para> 276 </caution> 277<!-- 278 <para>In screenshot 3 below, the chromaticities match, but the channel 279 encoding does not match:</para> 280 <mediaobject> 281 <imageobject> 282 <imagedata fileref="images/menus/image/color-management/enable-cm-linear-precision-mismatched-channel-encoding.png" format="PNG"/> 283 </imageobject> 284 </mediaobject> 285 <para>In screenshot 3 above, the sRGB-elle-V4-srgbtrc.icc chromaticities 286 match the chromaticities of the GIMP built-in linear sRGB profile, but the 287 sRGB-elle-V4-srgbtrc.icc profile channel encoding doesn't match the current 288 GIMP linear channel encoding. So after unchecking Enable Color 289 Management, the colors are correct but the tonality is wrong.</para> 290 <para>In screenshot 4 below, both the channel encoding and chromaticities 291 are mismatched:</para> 292 <mediaobject> 293 <imageobject> 294 <imagedata fileref="images/menus/image/color-management/enable-cm-mismatched-chromaticities-and-channel-encoding.png" format="PNG"/> 295 </imageobject> 296 </mediaobject> 297 <para>In Screenshot 4 above, the channel encoding of the original 298 LargeRGB-elle-V4-g10.icc profile is linear, but GIMP is using the 299 Perceptual gamma (sRGB) encoding. Also the LargeRGB-elle-V4-g10.icc 300 chromaticities don't match the GIMP built-in sRGB chromaticities. 301 So after unchecking Enable Color Management, the tonality is 302 wrong (it's too dark) and the colors are wrong.</para>--> 303 </sect3> 304 305</sect2> 306