1,584
This function takes a percentage value and calculates the RGB color. This is useful for a graph or table in which you want the background or some other indicator to change based on the value.
The problem I spent most of my time on was the loss of yellow.
The code is documented and should be easy to understand. Post any questions or modifications to this post.
License: GPL Public
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- /**
- * Example of use of percent2Color function
- * @author Dan M
- * @date 06/24/2010
- *
- *
- */
- /**
- * This function takes a value and returns an RGB color between Red to Yellow to Green in a given spectrum.
- * 50% = FFFF00
- *
- * @param mixed $value required
- * @param mixed $brightness value between 1 and 255
- * @param mixed $max default 100
- * @param mixed $min default 0
- * @param mixed $thirdColorHex '00'
- */
- function percent2Color($value,$brightness = 255, $max = 100,$min = 0, $thirdColorHex = '00')
- {
- // Calculate first and second color (Inverse relationship)
- $first = (1-($value/$max))*$brightness;
- $second = ($value/$max)*$brightness;
- // Find the influence of the middle color (yellow if 1st and 2nd are red and green)
- $diff = abs($first-$second);
- $influence = ($brightness-$diff)/2;
- $first = intval($first + $influence);
- $second = intval($second + $influence);
- // Convert to HEX, format and return
- $firstHex = str_pad(dechex($first),2,0,STR_PAD_LEFT);
- $secondHex = str_pad(dechex($second),2,0,STR_PAD_LEFT);
- return $firstHex . $secondHex . $thirdColor ;
- // alternatives:
- // return $thirdColorHex . $firstHex . $secondHex;
- // return $firstHex . $thirdColorHex . $secondHex;
- }
If you would like to compact it or add to it, go ahead and post the new version back! You can also change the affecting pair from red-green to green-blue or blue-red with a red hue or green hue as alternative if you want.
Cheers,
Dan M.
Example of use:
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- <html>
- <body>
- <table width="300px">
- <tr><td>Percent</td><td>Color</td></tr>
- <?php
- $example = array(10,40,28,69,100,0,50);
- foreach($example as $x)
- {
- $color = percent2Color($x,$brightness = 200);
- echo "<tr><td>$x</td><td style='background-color:#$color'>$color</td>";
- }
- ?>
- </table>
- </body>
- </html>
- </html>
