{"id":3001,"date":"2011-12-09T09:10:13","date_gmt":"2011-12-09T14:10:13","guid":{"rendered":"https:\/\/blogs.mathworks.com\/pick\/?p=3001"},"modified":"2021-09-22T15:27:20","modified_gmt":"2021-09-22T19:27:20","slug":"a-vivid-colormap","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/pick\/2011\/12\/09\/a-vivid-colormap\/","title":{"rendered":"A Vivid Colormap"},"content":{"rendered":"
\r\n\r\nJiro<\/a>'s pick this week is Vivid Colormap<\/a> by Joseph Kirk<\/a>.\r\n\r\nGood uses of colors can help convey ideas effectively. It can help you accentuate certain concepts. Or you may need to use\r\na gradient color that translates well when printed in gray scale. Joseph's entry really caught my attention. As the name suggests,\r\nit produces quite a vivid colormap. The idea is ingenious; he creates a gradient within each color, and that produces an accent\r\nat each level.\r\n\r\nLet's see how it works. We'll first create a blue and red diverging color map, which gradually changes from blue to red with\r\nwhite in the center. We'll use the peaks<\/tt><\/a> function as the sample image.\r\n
% Create 13-level blue\/red diverging color map:<\/span>\r\nlevel = 13; n = ceil(level\/2);\r\ncmap1 = [linspace(1, 1, n); linspace(0, 1, n); linspace(0, 1, n)]';\r\ncmap2 = [linspace(1, 0, n); linspace(1, 0, n); linspace(1, 1, n)]';\r\ncmap = [cmap1; cmap2(2:end, :)];\r\n\r\nimagesc(peaks(500));\r\ncolormap(vivid(cmap)); caxis([-8 8]);\r\ncolorbar<\/pre>\r\n\"\"\r\n\r\nNotice how vivid it looks! vivid<\/tt> also has additional options to change the level of gradients.\r\n\r\nLess vivid:\r\n
colormap(vivid(cmap, [.4, .6]));<\/pre>\r\n\"\"\r\n\r\nMore vivid:\r\n
colormap(vivid(cmap, [0, 1]));<\/pre>\r\n\"\"\r\n\r\nYou can also get the regular colormap behavior:\r\n
colormap(vivid(cmap, [.5 .5]));<\/pre>\r\n\"\"\r\n\r\nMore on Colormaps<\/b>\r\n\r\nAs I was writing this post, I learned quite a bit about colormaps. MATLAB has a set of standard colormaps described here<\/a>. There are a few File Exchange entries that create additional colormaps, such as cbrewer<\/tt><\/a>, othercolor<\/tt><\/a>, and Color Palette Tables<\/a>. There are also colormaps that would look nice when printed on a grayscale printer - Lab color scale and colorGray<\/tt><\/a>.\r\n\r\nI also found a couple of entries that would have helped me with creating the blue\/red diverging colormap - bluewhitered<\/tt><\/a> and makeColorMap<\/tt><\/a>.\r\n\r\nComments<\/b>\r\n\r\nCheck out all the File Exchange entries on colormaps<\/a>! If you have your favorite colormap, let us know here<\/a> or try Joseph's vivid<\/tt> and leave a comment for him.\r\n\r\n