generate smooth hex gradient table - php

Question

generate list of hex colours?
Hi there,
Currently I am trying to generate a list of 50 hex colours that create a roughly smooth gradient from white to black, with all the colours in between.
How would I go about doing this in php?

Answer 1

Well,
Although The colours could prob be in a better order,
Here was my working.
<?php
function Gradient($HexFrom, $HexTo, $ColorSteps) {
$FromRGB['r'] = hexdec(substr($HexFrom, 0, 2));
$FromRGB['g'] = hexdec(substr($HexFrom, 2, 2));
$FromRGB['b'] = hexdec(substr($HexFrom, 4, 2));
$ToRGB['r'] = hexdec(substr($HexTo, 0, 2));
$ToRGB['g'] = hexdec(substr($HexTo, 2, 2));
$ToRGB['b'] = hexdec(substr($HexTo, 4, 2));
$StepRGB['r'] = ($FromRGB['r'] - $ToRGB['r']) / ($ColorSteps - 1);
$StepRGB['g'] = ($FromRGB['g'] - $ToRGB['g']) / ($ColorSteps - 1);
$StepRGB['b'] = ($FromRGB['b'] - $ToRGB['b']) / ($ColorSteps - 1);
$GradientColors = array();
for($i = 0; $i <= $ColorSteps; $i++) {
$RGB['r'] = floor($FromRGB['r'] - ($StepRGB['r'] * $i));
$RGB['g'] = floor($FromRGB['g'] - ($StepRGB['g'] * $i));
$RGB['b'] = floor($FromRGB['b'] - ($StepRGB['b'] * $i));
$HexRGB['r'] = sprintf('%02x', ($RGB['r']));
$HexRGB['g'] = sprintf('%02x', ($RGB['g']));
$HexRGB['b'] = sprintf('%02x', ($RGB['b']));
$GradientColors[] = implode(NULL, $HexRGB);
}
$GradientColors = array_filter($GradientColors, "len");
return $GradientColors;
}
function len($val){
return (strlen($val) == 6 ? true : false );
}
$count = 0;
$steps = 9;
$Gradients = Gradient("FFFFFF", "FF0000", $steps);
foreach($Gradients as $Gradient)
echo '<div style="background-color: #' . strtoupper($Gradient) . '">' . htmlentities('<option value="' . strtoupper($Gradient) . '">' . strtoupper($Gradient) . '</option>') . '</div>';
$count += count($Gradients);
$Gradients = Gradient("df1f00", "00FF00", $steps);
foreach($Gradients as $Gradient)
echo '<div style="background-color: #' . strtoupper($Gradient) . '">' . htmlentities('<option value="' . strtoupper($Gradient) . '">' . strtoupper($Gradient) . '</option>') . '</div>';
$count += count($Gradients);
$Gradients = Gradient("00df1f", "0000FF", $steps);
foreach($Gradients as $Gradient)
echo '<div style="background-color: #' . strtoupper($Gradient) . '">' . htmlentities('<option value="' . strtoupper($Gradient) . '">' . strtoupper($Gradient) . '</option>') . '</div>';
$count += count($Gradients);
$Gradients = Gradient("0000df", "000000", $steps);
foreach($Gradients as $Gradient)
echo '<div style="background-color: #' . $Gradient . '">' . htmlentities('<option value="' . $Gradient . '">' . $Gradient . '</option>') . '</div>';
$count += count($Gradients);
echo 'count: ' . $count;

Answer 2

with all the colours in between
You can find a path from white to black but you will have a difficult time including all colours - colour space is 3-dimensional, not linear.
You could look at this for some ideas:
http://www.exorithm.com/algorithm/view/create_gradient

Answer 3

Here is some customisation of the function, it's also handle case only 1 or 2 graduation needed, and also remove # on hexa before calculs and send back an array of color starting with #. so that can be directly applied to a content.
public function gradient($from_color, $to_color, $graduations = 10) {
$graduations--;
$startcol = str_replace("#", "", $from_color);
$endcol = str_replace("#", "", $to_color);
$RedOrigin = hexdec(substr($startcol, 0, 2));
$GrnOrigin = hexdec(substr($startcol, 2, 2));
$BluOrigin = hexdec(substr($startcol, 4, 2));
if ($graduations >= 2) { // for at least 3 colors
$GradientSizeRed = (hexdec(substr($endcol, 0, 2)) - $RedOrigin) / $graduations; //Graduation Size Red
$GradientSizeGrn = (hexdec(substr($endcol, 2, 2)) - $GrnOrigin) / $graduations;
$GradientSizeBlu = (hexdec(substr($endcol, 4, 2)) - $BluOrigin) / $graduations;
for ($i = 0; $i <= $graduations; $i++) {
$RetVal[$i] = strtoupper("#" . str_pad(dechex($RedOrigin + ($GradientSizeRed * $i)), 2, '0', STR_PAD_LEFT) .
str_pad(dechex($GrnOrigin + ($GradientSizeGrn * $i)), 2, '0', STR_PAD_LEFT) .
str_pad(dechex($BluOrigin + ($GradientSizeBlu * $i)), 2, '0', STR_PAD_LEFT));
}
} elseif ($graduations == 1) { // exactlly 2 colors
$RetVal[] = $from_color;
$RetVal[] = $to_color;
} else { // one color
$RetVal[] = $from_color;
}
return $RetVal;
}

Answer 4

Also could be helpful to take a look at my answer here.
It has the code to convert any number from any given range (let's say [0,20]) to particular color where 0 is red, 10 is yellow, 20 is green. You can use any colors and even use combination of 4 colors, so it's red - yellow - green - blue.

Answer 5

function rgb2hex($rgb) {
$hex = "#";
$hex .= str_pad(dechex($rgb[0]), 2, "0", STR_PAD_LEFT);
$hex .= str_pad(dechex($rgb[1]), 2, "0", STR_PAD_LEFT);
$hex .= str_pad(dechex($rgb[2]), 2, "0", STR_PAD_LEFT);
return $hex; // returns the hex value including the number sign (#)
}
function dif($c1, $c2, $percent) {
$array=array();
for($x=0;$x<3;$x++) {
$d=($c2[$x]-$c1[$x])*$percent+$c1[$x];
$array[]=(int)$d;
}
return $array;
}
for($x=0;$x<=255;$x++) {
echo rgb2hex( dif(array(255,255,255), array(0,0,0), $x/255 /*percent*/) );
echo "<br>";
}