A distance of '1' is the maximum distance in the color space e.g. from 0, 0, 0 to 255, 255, 255 in RGB color space.
The only difference between ImagickPixel::isSimilar and ImagickPixel::isPixelSimilar is that isSimilar needs to be scaled by the quantum value.
| Color 1 | Color 2 | Test distance * 255 | Is within distance |
|---|---|---|---|
| rgb(245, 0, 0) | rgb(255, 0, 0) | 5.196152423 | no |
| rgb(245, 0, 0) | rgb(255, 0, 0) | 5.773502692 | yes |
| rgb(0, 0, 0) | rgb(7, 7, 0) | 5.196152423 | no |
| rgb(0, 0, 0) | rgb(7, 7, 0) | 5.773502692 | yes |
| rgba(0, 0, 0, 1) | rgba(7, 7, 0, 1) | 5.196152423 | no |
| rgba(0, 0, 0, 1) | rgba(7, 7, 0, 1) | 5.773502692 | yes |
| rgb(128, 128, 128) | rgb(128, 128, 120) | 4.041451884 | no |
| rgb(128, 128, 128) | rgb(128, 128, 120) | 4.618802154 | yes |
| rgb(0, 0, 0) | rgb(255, 255, 255) | 254.9 | no |
| rgb(0, 0, 0) | rgb(255, 255, 255) | 255 | yes |
| rgb(255, 0, 0) | rgb(0, 255, 255) | 254.9 | no |
| rgb(255, 0, 0) | rgb(0, 255, 255) | 255 | yes |
| black | rgba(0, 0, 0) | 0 | yes |
| black | rgba(10, 0, 0, 1.0) | 5.773502692 | yes |
// Example 1
// The tests below are written with the maximum distance expressed as 255
// so we need to scale them by the square root of 3 - the diagonal length
// of a unit cube.
$root3 = 1.732050807568877;
$tests = array(
['rgb(245, 0, 0)', 'rgb(255, 0, 0)', 9 / $root3, false,],
['rgb(245, 0, 0)', 'rgb(255, 0, 0)', 10 / $root3, true,],
['rgb(0, 0, 0)', 'rgb(7, 7, 0)', 9 / $root3, false,],
['rgb(0, 0, 0)', 'rgb(7, 7, 0)', 10 / $root3, true,],
['rgba(0, 0, 0, 1)', 'rgba(7, 7, 0, 1)', 9 / $root3, false,],
['rgba(0, 0, 0, 1)', 'rgba(7, 7, 0, 1)', 10 / $root3, true,],
['rgb(128, 128, 128)', 'rgb(128, 128, 120)', 7 / $root3, false,],
['rgb(128, 128, 128)', 'rgb(128, 128, 120)', 8 / $root3, true,],
['rgb(0, 0, 0)', 'rgb(255, 255, 255)', 254.9, false,],
['rgb(0, 0, 0)', 'rgb(255, 255, 255)', 255, true,],
['rgb(255, 0, 0)', 'rgb(0, 255, 255)', 254.9, false,],
['rgb(255, 0, 0)', 'rgb(0, 255, 255)', 255, true,],
['black', 'rgba(0, 0, 0)', 0.0, true],
['black', 'rgba(10, 0, 0, 1.0)', 10.0 / $root3, true],);
$output = "<table width='100%' class='infoTable'><thead>
<tr>
<th>
Color 1
</th>
<th>
Color 2
</th>
<th>
Test distance * 255
</th>
<th>
Is within distance
</th>
</tr>
</thead>";
$output .= "<tbody>";
foreach ($tests as $testInfo) {
$color1 = $testInfo[0];
$color2 = $testInfo[1];
$distance = $testInfo[2];
$expectation = $testInfo[3];
$testDistance = ($distance / 255.0);
$color1Pixel = new \ImagickPixel($color1);
$color2Pixel = new \ImagickPixel($color2);
$isSimilar = $color1Pixel->isPixelSimilar($color2Pixel, $testDistance);
if ($isSimilar !== $expectation) {
echo "Test distance failed. Color [$color1] compared to color [$color2] is not within distance $testDistance FAILED." . NL;
}
$layout = "<tr>
<td>%s</td>
<td>%s</td>
<td>%s</td>
<td style='text-align: center;'>%s</td>
</tr>";
$output .= sprintf(
$layout,
$color1,
$color2,
$distance,
$isSimilar ? 'yes' : 'no'
);
}
$output .= "</tbody></table>";
return $output;
// Example 2
// The tests below are written with the maximum distance expressed as 255
// so we need to scale them by the square root of 3 - the diagonal length
// of a unit cube.
$root3 = 1.732050807568877;
$quantum = \Imagick::getQuantum();
$tests = array(
['rgb(245, 0, 0)', 'rgb(255, 0, 0)', 9 / $root3, false,],
['rgb(245, 0, 0)', 'rgb(255, 0, 0)', 10 / $root3, true,],
['rgb(0, 0, 0)', 'rgb(7, 7, 0)', 9 / $root3, false,],
['rgb(0, 0, 0)', 'rgb(7, 7, 0)', 10 / $root3, true,],
['rgba(0, 0, 0, 1)', 'rgba(7, 7, 0, 1)', 9 / $root3, false,],
['rgba(0, 0, 0, 1)', 'rgba(7, 7, 0, 1)', 10 / $root3, true,],
['rgb(128, 128, 128)', 'rgb(128, 128, 120)', 7 / $root3, false,],
['rgb(128, 128, 128)', 'rgb(128, 128, 120)', 8 / $root3, true,],
['rgb(0, 0, 0)', 'rgb(255, 255, 255)', 254.9, false,],
['rgb(0, 0, 0)', 'rgb(255, 255, 255)', 255, true,],
['rgb(255, 0, 0)', 'rgb(0, 255, 255)', 254.9, false,],
['rgb(255, 0, 0)', 'rgb(0, 255, 255)', 255, true,],
['black', 'rgba(0, 0, 0)', 0.0, true],
['black', 'rgba(10, 0, 0, 1.0)', 10.0 / $root3, true],);
$output = "<table width='100%' class='infoTable'><thead>
<tr>
<th>
Color 1
</th>
<th>
Color 2
</th>
<th>
Test distance * 255
</th>
<th>
Is within distance
</th>
</tr>
</thead>";
$output .= "<tbody>";
foreach ($tests as $testInfo) {
$color1 = $testInfo[0];
$color2 = $testInfo[1];
$distance = $testInfo[2];
$expectation = $testInfo[3];
$testDistance = ($distance / 255.0);
$color1Pixel = new \ImagickPixel($color1);
$color2Pixel = new \ImagickPixel($color2);
$isSimilar = $color1Pixel->isPixelSimilarQuantum($color2Pixel, $quantum * $testDistance);
if ($isSimilar !== $expectation) {
echo "Test distance failed. Color [$color1] compared to color [$color2] is not within distance $testDistance FAILED." . NL;
}
$layout = "<tr>
<td>%s</td>
<td>%s</td>
<td>%s</td>
<td style='text-align: center;'>%s</td>
</tr>";
$output .= sprintf(
$layout,
$color1,
$color2,
$distance,
$isSimilar ? 'yes' : 'no'
);
}
$output .= "</tbody></table>";
return $output;