{"id":26,"date":"2012-02-26T23:37:53","date_gmt":"2012-02-26T23:37:53","guid":{"rendered":"http:\/\/beta.robertprice.co.uk\/robblog\/2012\/02\/adding_colour_to_a_mandelbrot_set-shtml\/"},"modified":"2012-02-26T23:37:53","modified_gmt":"2012-02-26T23:37:53","slug":"adding_colour_to_a_mandelbrot_set-shtml","status":"publish","type":"post","link":"https:\/\/www.robertprice.co.uk\/robblog\/adding_colour_to_a_mandelbrot_set-shtml\/","title":{"rendered":"Adding Colour To A Mandelbrot Set"},"content":{"rendered":"

\nI was looking for a way to introduce some colour into my example Drawing A Mandelbrot Set With Zend PDF<\/a>.\n<\/p>\n

\nThe method I settled upon was to use HSV – Hue, Saturation, Value.\n<\/p>\n

\nI’m not an expert on colour theory, so I may not be the best person to describe how it works. The best way I can though, is to describe it as a cylinder, round the circumference is the hue, the radius is the saturation, and the height is the value. For a detailed definition, read the Wikipedia entry on HSL and HSV<\/a>.\n<\/p>\n

\nI can pick a hue and value, then just vary the saturation to give a nice graduated colour version of the earlier grayscale example.\n<\/p>\n

\n\"Blue\n<\/p>\n

\nAlternatively I can pick a value and saturation, and vary the hue to give a vivid rainbow style fractal.\n<\/p>\n

\n\"Vivid\n<\/p>\n

\nTo achieve the first, we replace the code in the loop that prepared the grayscale colours, and instead generate our $colours<\/var> array with the following…\n<\/p>\n

list($red, $green, $blue) = hsvToRgb(0.5, $grayLevel, 1);\n$colours[$i] = new Zend_Pdf_Color_Rgb($red, $green, $blue);\n<\/pre>\n
\nFirstly we get the values for $red<\/var>, $green<\/var> and $blue<\/var> for a hue of 0.5 (blue), our varying $graylevel between 0 and 1, and a $value of 1 for the most vivid colours. After this we create a Zend_Pdf_Color<\/var> and store it in the $colours<\/var> array to use later.\n<\/p>\n
\nTo achieve the latter we just change how we call the hsvToRgb<\/code> function.\n<\/p>\n
list($red, $green, $blue) = hsvToRgb($grayLevel, 1, 1);\n$colours[$i] = new Zend_Pdf_Color_Rgb($red, $green, $blue);\n<\/pre>\n
\nNow, you may have noticed that there isn’t a function called hsvToRgb<\/code> available to PHP. Just drop in the following code.\n<\/p>\n
function hsvToRgb ($hue, $saturation, $value)\n{\n  $rgb = array($value, $value, $value);\n  if ($saturation != 0) {\n    $varH = $hue * 6;\n    $varI = floor($varH);\n    $var1 = $value * ( 1 - $saturation );\n    $var2 = $value * ( 1 - $saturation * ( $varH - $varI ) );\n    $var3 = $value * ( 1 - $saturation * (1 - ( $varH - $varI ) ) );\n    if ($varI == 0) {\n      $rgb = array($value, $var3, $var1);\n    } else if ($varI == 1) {\n      $rgb = array($var2, $value, $var1);\n    } else if ($varI == 2) {\n      $rgb = array($var1, $value, $var3);\n    } else if ($varI == 3) {\n      $rgb = array($var1, $var2, $value);\n    } else if ($varI == 4) {\n      $rgb = array($var3, $var1, $value);\n    } else {\n      $rgb = array($value, $var1, $var2);\n    }\n  }\n  return $rgb;\n}\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
I was looking for a way to introduce some colour into my example Drawing A Mandelbrot Set With Zend PDF. The method I settled upon was to use HSV – Hue, Saturation, Value. I’m not an expert on colour theory, so I may not be the best person to describe how it works. The best … Continue reading “Adding Colour To A Mandelbrot Set”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[2],"tags":[50,81],"class_list":["post-26","post","type-post","status-publish","format-standard","hentry","category-dev","tag-php","tag-zend-framework"],"yoast_head":"\nAdding Colour To A Mandelbrot Set - Robert Price<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.robertprice.co.uk\/robblog\/adding_colour_to_a_mandelbrot_set-shtml\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Adding Colour To A Mandelbrot Set - Robert Price\" \/>\n<meta property=\"og:description\" content=\"I was looking for a way to introduce some colour into my example Drawing A Mandelbrot Set With Zend PDF. 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