imagecolorclosest

(PHP 4, PHP 5, PHP 7)

Get the index of the closest color to the specified color

int imagecolorclosest ( resource $image, int $red, int $green, int $blue )

Returns the index of the color in the palette of the image which is "closest" to the specified RGB value.

The "distance" between the desired color and each color in the palette is calculated as if the RGB values represented points in three-dimensional space.

If you created the image from a file, only colors used in the image are resolved. Colors present only in the palette are not resolved.

Parameters:

image

An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().

red

Value of red component.

green

Value of green component.

blue

Value of blue component.

Returns:

Returns the index of the closest color, in the palette of the image, to the specified one

Examples:

Search for a set of colors in an image

<?php
// Start with an image and convert it to a palette-based image
$im = imagecreatefrompng('figures/imagecolorclosest.png');
imagetruecolortopalette($im, false, 255);

// Search colors (RGB)
$colors = array(
    array(254, 145, 154),
    array(153, 145, 188),
    array(153, 90, 145),
    array(255, 137, 92)
);

// Loop through each search and find the closest color in the palette.
// Return the search number, the search RGB and the converted RGB match
foreach($colors as $id => $rgb)
{
    $result = imagecolorclosest($im, $rgb[0], $rgb[1], $rgb[2]);
    $result = imagecolorsforindex($im, $result);
    $result = "({$result['red']}, {$result['green']}, {$result['blue']})";

    echo "#$id: Search ($rgb[0], $rgb[1], $rgb[2]); Closest match: $result.\n";
}

imagedestroy($im);
?>

The above example will output something similar to:

#0: Search (254, 145, 154); Closest match: (252, 150, 148).
#1: Search (153, 145, 188); Closest match: (148, 150, 196).
#2: Search (153, 90, 145); Closest match: (148, 90, 156).
#3: Search (255, 137, 92); Closest match: (252, 150, 92).