{"id":117,"date":"2016-06-14T21:30:04","date_gmt":"2016-06-14T21:30:04","guid":{"rendered":"http:\/\/www.blackestknight.com\/photography\/?p=117"},"modified":"2022-06-10T23:05:39","modified_gmt":"2022-06-10T22:05:39","slug":"5-8-curves","status":"publish","type":"post","link":"https:\/\/www.blackestknight.com\/index.php\/2016\/06\/14\/5-8-curves\/","title":{"rendered":"5.8.\u00a0Curves"},"content":{"rendered":"<p><img decoding=\"async\" loading=\"lazy\" class=\"size-medium wp-image-123 aligncenter\" src=\"http:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/07\/site-icon-300x300.png\" alt=\"site-icon\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/07\/site-icon-300x300.png 300w, https:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/07\/site-icon-150x150.png 150w, https:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/07\/site-icon-500x500.png 500w, https:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/07\/site-icon.png 512w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/>Source: <em><a href=\"https:\/\/docs.gimp.org\/en\/gimp-tool-curves.html\">5.8.\u00a0Curves<\/a><\/em><\/p>\n<div class=\"sect2\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h3 class=\"title\"><a id=\"gimp-tool-curves\"><\/a>5.8. Curves<\/h3>\n<\/div>\n<\/div>\n<\/div>\n<p><a id=\"idp14924784\" class=\"indexterm\"><\/a><br \/>\n<a id=\"idp16955072\" class=\"indexterm\"><\/a><\/p>\n<p>The Curves tool is the most sophisticated tool for changing the color,<br \/>\nbrightness, contrast or transparency of the active layer or a selection.<br \/>\nWhile the Levels tool allows you to work on Shadows and Highlights, the<br \/>\nCurves tool allows you to work on any tonal range. It works on RGB<br \/>\nimages.<\/p>\n<div class=\"sect3\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h4 class=\"title\"><a id=\"idp13704320\"><\/a>5.8.1. Activating the Tool<\/h4>\n<\/div>\n<\/div>\n<\/div>\n<p>You can get to this tool in several ways:<\/p>\n<div class=\"itemizedlist\">\n<ul class=\"itemizedlist\" style=\"list-style-type: disc;\">\n<li class=\"listitem\">In the image menu through<br \/>\n<span class=\"guimenu\">Tools<\/span> \u2192 <span class=\"guisubmenu\">Color Tools<\/span> \u2192 <span class=\"guimenuitem\">Curves<\/span> or<br \/>\n<span class=\"guimenu\">Colors<\/span> \u2192 <span class=\"guimenuitem\">Curves<\/span>.<\/li>\n<li class=\"listitem\">By clicking on the tool icon<br \/>\n<span class=\"guiicon\"><\/p>\n<p><\/span><br \/>\nin Toolbox, if this tool has been installed there. For this, please<br \/>\nrefer to Section 1.7, \u201cToolbox\u201d.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div class=\"sect3\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h4 class=\"title\"><a id=\"idp19190976\"><\/a>5.8.2. <span class=\"quote\">\u201c<span class=\"quote\">Adjust Color Curves<\/span>\u201d<\/span> options<\/h4>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"figure\"><\/div>\n<\/div>\n<\/div>\n<p class=\"title\"><strong>Figure 14.168. The <span class=\"quote\">\u201c<span class=\"quote\">Adjust Color Curves<\/span>\u201d<\/span> dialog<\/strong><\/p>\n<div class=\"figure-contents\">\n<div class=\"mediaobject\"><\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Presets<\/span><\/dt>\n<dd>You can save the color settings of your image by clicking the<br \/>\n<span class=\"guibutton\">Add settings to favourites<\/span> button<br \/>\n<span class=\"guiicon\"><\/p>\n<p><\/span>The<br \/>\n<span class=\"guiicon\"><\/p>\n<p><\/span><br \/>\nbutton opens a menu:<\/p>\n<div class=\"figure\">\n<p>&nbsp;<\/p>\n<p class=\"title\"><strong>Figure 14.169. Preset Menu<\/strong><\/p>\n<div class=\"figure-contents\">\n<div class=\"mediaobject\"><\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>which lets you <span class=\"guilabel\">Import Settings from File<\/span> or<br \/>\n<span class=\"guilabel\">Export Settings to File<\/span>,<br \/>\nand gives you access to the Manage Save Settings dialog:<\/p>\n<div class=\"figure\">\n<p>&nbsp;<\/p>\n<p class=\"title\"><strong>Figure 14.170. Manage saved Settings Dialog<\/strong><\/p>\n<div class=\"figure-contents\">\n<div class=\"mediaobject\"><\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/dd>\n<dt><span class=\"term\">Channel<\/span><\/dt>\n<dd>\n<div class=\"variablelist\">\n<p>There are five options:<\/p>\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Value<\/span><\/dt>\n<dd>The curve represents the Value, i.e. the brightness of<br \/>\npixels as you can see them in the composite image.<\/dd>\n<dt><span class=\"term\">Red; Green; Blue<\/span><\/dt>\n<dd>The curve represents the quantity of color in each of the<br \/>\nthree RGB channels. Here, <span class=\"emphasis\"><em>dark<\/em><\/span> means<br \/>\n<span class=\"emphasis\"><em>little<\/em><\/span> of the color.<br \/>\n<span class=\"emphasis\"><em>Light<\/em><\/span> means <span class=\"emphasis\"><em>a lot<\/em><\/span><br \/>\nof the color.<\/dd>\n<dt><span class=\"term\">Alpha<\/span><\/dt>\n<dd>The curve represents the opacity of the pixels.<br \/>\n<span class=\"emphasis\"><em>Dark<\/em><\/span> means<br \/>\n<span class=\"emphasis\"><em>very transparent<\/em><\/span>.<br \/>\n<span class=\"emphasis\"><em>Light<\/em><\/span> means <span class=\"emphasis\"><em>very<br \/>\nopaque<\/em><\/span>. Your image or active layer must have<br \/>\nan Alpha channel for this option to be enabled.<\/dd>\n<\/dl>\n<\/div>\n<\/dd>\n<dt><span class=\"term\">Reset Channel<\/span><\/dt>\n<dd>This button deletes all changes made to the selected channel and<br \/>\nreturns to default values.<\/dd>\n<dt><span class=\"term\">Linear and Logarithmic buttons<\/span><\/dt>\n<dd>These buttons allow to choose the Linear or Logarithmic type of<br \/>\nthe histogram. You can also use the same options in Tool Options<br \/>\ndialog. This grayed out histogram is not displayed by default.<\/dd>\n<dt><span class=\"term\">Main Editing Area<\/span><\/dt>\n<dd>\n<div class=\"itemizedlist\">\n<ul class=\"itemizedlist\" style=\"list-style-type: disc;\">\n<li class=\"listitem\"><span class=\"emphasis\"><em>The horizontal gradient<\/em><\/span>: it represents<br \/>\nthe input tonal scale. It, too, ranges from 0 (black) to 255<br \/>\n(white), from Shadows to Highlights. When you<br \/>\nadjust the curve, it splits up into two parts; the upper part<br \/>\nthen represents the <span class=\"emphasis\"><em>tonal balance<\/em><\/span> of the<br \/>\nlayer or selection.<\/li>\n<li class=\"listitem\"><span class=\"emphasis\"><em>The vertical gradient<\/em><\/span>: it represents the<br \/>\ndestination, the output tonal scale. It ranges from 0 (black)<br \/>\nto 255 (white), from Shadows to Highlights.<\/li>\n<li class=\"listitem\"><span class=\"emphasis\"><em>The chart<\/em><\/span>: the curve is drawn on a grid<br \/>\nand goes from the bottom left corner to the top right corner.<br \/>\nThe pointer x\/y position is permanently displayed in the top<br \/>\nleft part of the grid. By default, this curve is straight,<br \/>\nbecause every input level corresponds to the same<br \/>\nouput tone. GIMP automatically places an anchor at both<br \/>\nends of the curve, for black (0) and white (255).If you click on the curve, a new <span class=\"emphasis\"><em>anchor<\/em><\/span><br \/>\nis created. When the mouse pointer goes over an anchor, it<br \/>\ntakes the form of a small hand. You can<br \/>\nclick-and-drag the anchor to bend the curve. If you click<br \/>\noutside of the curve, an anchor is also created, and the<br \/>\ncurve includes it automatically.<\/p>\n<p>Unactive anchors are black. The active anchor is white. You<br \/>\ncan activate an anchor by clicking on it. You can also swap<br \/>\nthe anchor activation by using the Left and Right arrow keys<br \/>\nof your keyboard. You can move the anchor vertically with the<br \/>\nUp and Down arrow keys. This allows you to fine tune the<br \/>\nanchor position. Holding the <span class=\"keycap\"><strong>Shift<\/strong><\/span> down lets<br \/>\nyou move it by increments of 15 pixels.<\/p>\n<p>Two anchors define a <span class=\"emphasis\"><em>curve segment<\/em><\/span> which<br \/>\nrepresents a tonal range in the layer. You can click-and-drag<br \/>\nthis segment (this creates a new anchor). Of course, you<br \/>\ncan&#8217;t drag it beyond the end anchors.<\/p>\n<p>To delete all anchors (apart from both ends), click on the<br \/>\n<span class=\"guilabel\">Reset Channel<\/span> button. To delete only one<br \/>\nanchor, move beyond any adjacent anchor on horizontal axis.<\/p>\n<p>Meanwhile, on the canvas, the mouse pointer has the form of<br \/>\nan eye-dropper. If you click on a pixel, a vertical line<br \/>\nappears on the chart, positioned to the source value of this<br \/>\npixel in the selected channel. If you<br \/>\n<span class=\"keycap\"><strong>Shift<\/strong><\/span>-click, you create an anchor in the<br \/>\nselected channel. If you <span class=\"keycap\"><strong>Ctrl<\/strong><\/span>-click, you<br \/>\ncreate an anchor in all channels, possibly including the<br \/>\nAlpha channel. You can also <span class=\"keycap\"><strong>Shift<\/strong><\/span>-drag and<br \/>\n<span class=\"keycap\"><strong>Ctrl<\/strong><\/span>-drag: this<br \/>\nwill move the vertical line and the anchor will show up when<br \/>\nreleasing the mouse left button.<\/p>\n<p>The histogram of the active layer or selection for the<br \/>\nselected channel is represented grayed out in the chart. It&#8217;s<br \/>\nonly a reference.<\/li>\n<\/ul>\n<\/div>\n<\/dd>\n<dt><span class=\"term\">Curve type<\/span><\/dt>\n<dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Smooth<\/span><\/dt>\n<dd>This the default mode. It constrains the curve type to a<br \/>\nsmooth line with tension. It provides a more realistic<br \/>\nrender than the following.<\/dd>\n<dt><span class=\"term\">Free Hand<\/span><\/dt>\n<dd>With this mode, you can draw a broken line that you can<br \/>\nsmooth by clicking the <span class=\"guibutton\">Curve Type<\/span><br \/>\nbutton again.<\/dd>\n<\/dl>\n<\/div>\n<\/dd>\n<dt><span class=\"term\">Preview<\/span><\/dt>\n<dd>The Preview button makes all changes to the levels dynamically so<br \/>\nthat the new level settings can be viewed immediately.<\/dd>\n<\/dl>\n<\/div>\n<div class=\"variablelist\">\n<p class=\"title\"><strong>Tool Options dialog<\/strong><\/p>\n<p>Although this tool is not present in the Toolbox by default (For this,<br \/>\nplease refer to Section 1.7, \u201cToolbox\u201d if you want to add<br \/>\nit), nevertheless it has a Tool Option Dialog under the Toolbox. These<br \/>\noptions are described here:<\/p>\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Histogram Scale<\/span><\/dt>\n<dd>These two options have the same action as the Logarithmic<br \/>\n<span class=\"guiicon\"><\/p>\n<p><\/span><br \/>\nand Linear<br \/>\n<span class=\"guiicon\"><\/p>\n<p><\/span><br \/>\nbuttons in the Curves dialog.<\/dd>\n<dt><span class=\"term\">Sample Average<\/span><\/dt>\n<dd>This slider sets the <span class=\"quote\">\u201c<span class=\"quote\">radius<\/span>\u201d<\/span> of the color-picking<br \/>\narea. This area appears as a more or less enlarged square when you<br \/>\nmaintain the click on a pixel. Here, the eye-dropper is used to<br \/>\nlocate a pixel: radius = 1 seems the best.<\/dd>\n<\/dl>\n<\/div>\n<div class=\"sect3\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h4 class=\"title\"><a id=\"idp17823296\"><\/a>5.8.3. Using the <span class=\"quote\">\u201c<span class=\"quote\">Curves<\/span>\u201d<\/span> tool<\/h4>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"sect4\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h5 class=\"title\"><a id=\"idp19155008\"><\/a>5.8.3.1. Summary and basic shapes<\/h5>\n<\/div>\n<\/div>\n<\/div>\n<p>We create anchors and segments on the curve and we move them to<br \/>\nshape the curve. This curve maps <span class=\"quote\">\u201c<span class=\"quote\">input<\/span>\u201d<\/span> tones of<br \/>\nthe active layer or selection to <span class=\"quote\">\u201c<span class=\"quote\">output<\/span>\u201d<\/span> tones.<\/p>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp16299232\"><\/a>How the Curves tool works<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<p>Moving the anchor of a pixel upwards makes this pixel brighter.<\/p>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p lang=\"en\" xml:lang=\"en\">Moving the anchor upwards<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp17074352\"><\/a>Making the curve more horizontal<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<p>Making the curve more horizontal forces all the input tonal range to<br \/>\noccupy a shrunk output tonal range.<\/p>\n<p>The histogram shows the compression of pixels into the output range.<br \/>\nDarkest and brightest pixels disappeared: contrast decreases.<\/p>\n<div class=\"figure\">\n<p>&nbsp;<\/p>\n<p class=\"title\"><strong>Figure 14.171. Making the curve more horizontal<\/strong><\/p>\n<div class=\"figure-contents\">\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>Make the curve more horizontal<\/p>\n<\/div>\n<\/div>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>The resulting histogram<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp18604208\"><\/a>Making the curve more vertical<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<p>Moving the upper end point to the left and the lower end point to<br \/>\nthe right is the same as moving the white slider to the left and the<br \/>\nblack slider to the right in the Levels tool: all pixels whose value<br \/>\nis more than the white point (the flat part of the curve) are made<br \/>\nwhite (more colored \/ more opaque according to the selected<br \/>\nchannel). All pixels whose value is less than the black point (the<br \/>\nlower flattened curve) are made black (black \/ completely<br \/>\ntransparent). Pixels corresponding to points of the curve that have<br \/>\nmoved up are made lighter. Pixels corresponding to points of the<br \/>\ncurve that have moved down are made darker (green arrows). All<br \/>\nthese pixels will be extended to the whole output tonal range.<\/p>\n<p>The histogram shows the extension of values, from black (0) to White<br \/>\n(255): contrast is increased. Since the Value channel is selected,<br \/>\nchanges affect all color channels and colors increase.<\/p>\n<div class=\"figure\">\n<p>&nbsp;<\/p>\n<p class=\"title\"><strong>Figure 14.172. Making the curve more vertical<\/strong><\/p>\n<div class=\"figure-contents\">\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>Make the curve more vertical<\/p>\n<\/div>\n<\/div>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>Result and its histogram<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div class=\"sect4\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h5 class=\"title\"><a id=\"idp13926304\"><\/a>5.8.3.2. Practical cases<\/h5>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp13927040\"><\/a>Invert colors<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>Inverted curve<\/p>\n<\/div>\n<\/div>\n<p>Black is made White (fully colored \/ fully opaque). White is made<br \/>\nblack (black, fully transparent). All pixels adopt the complementary<br \/>\ncolor. Why that? Because subtracting the channel values from 255<br \/>\ngives the complementary color. For example: 19;197;248 a sky blue<br \/>\ngives 255-19; 255-197; 255-248 = 236;58;7, a bright red.<\/p>\n<\/div>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp10380528\"><\/a>Enhance contrast<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>Contrast enhanced<\/p>\n<\/div>\n<\/div>\n<p>Contrast is increased in mid tones because the curve is steeper<br \/>\nthere. Highlights and Shadows are increased but contrast is slightly<br \/>\nless in these areas because the curve is flatter.<\/p>\n<\/div>\n<div class=\"simplesect\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h6 class=\"title\"><a id=\"idp26673136\"><\/a>Working on color channels<\/h6>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"mediaobject\"><\/div>\n<p>For every channel, we moved the white point horizontally to the<br \/>\nleft, to the first Highlights. This lightens Highlights up. Then we<br \/>\nshaped the curve to lighten Mid tons and Shadows while keeping<br \/>\nblack.<\/p>\n<div class=\"mediaobject\">\n<div class=\"caption\">\n<p>The original image and the result<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"navfooter\">\n<hr \/>\n<table summary=\"Navigation footer\" width=\"100%\">\n<tbody>\n<tr>\n<td align=\"left\" width=\"40%\"><\/td>\n<td align=\"center\" width=\"20%\">\n<\/td>\n<td align=\"right\" width=\"40%\"><\/td>\n<\/tr>\n<tr>\n<td align=\"left\" valign=\"top\" width=\"40%\">5.7. Levels<\/td>\n<td align=\"center\" width=\"20%\">\n<\/td>\n<td align=\"right\" valign=\"top\" width=\"40%\">5.9. Posterize<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Report an error in Bugzilla<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Source: 5.8.\u00a0Curves 5.8. Curves The Curves tool is the most sophisticated tool for changing the color, brightness, contrast or transparency of the active layer or a selection. While the Levels tool allows you to work on Shadows and Highlights, the Curves tool allows you to work on any tonal range. It works on RGB images. [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":286,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"image","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_newsletter_tier_id":0,"footnotes":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[1],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.blackestknight.com\/photography\/wp-content\/uploads\/2016\/09\/IGP1725.jpg","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7UXrA-1T","_links":{"self":[{"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/posts\/117"}],"collection":[{"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/comments?post=117"}],"version-history":[{"count":32,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/posts\/117\/revisions"}],"predecessor-version":[{"id":1443,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/posts\/117\/revisions\/1443"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/media\/286"}],"wp:attachment":[{"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/media?parent=117"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/categories?post=117"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.blackestknight.com\/index.php\/wp-json\/wp\/v2\/tags?post=117"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}