imagecolorexact

    (PHP 4, PHP 5, PHP 7, PHP 8)

    imagecolorexact — Get the index of the specified color

    Description

    imagecolorexact(
        GdImage $image,
        int $red,
        int $green,
        int $blue
    ): int

    Returns the index of the specified color in the palette of the image.

    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

    A GdImage object, 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.

    Return Values

    Returns the index of the specified color in the palette, or -1 if the color does not exist.

    Changelog

    Version Description
    8.0.0 image expects a GdImage instance now; previously, a valid gd resource was expected.

    Examples

    Example #1 Get colors from the GD logo

    <?php
    // Setup an image
    $im = imagecreatefrompng('./gdlogo.png');

    $colors = Array();
    $colors[] = imagecolorexact($im, 255, 0, 0);
    $colors[] = imagecolorexact($im, 0, 0, 0);
    $colors[] = imagecolorexact($im, 255, 255, 255);
    $colors[] = imagecolorexact($im, 100, 255, 52);

    print_r($colors);

    // Free from memory
    imagedestroy($im);
    ?>

    The above example will output something similar to:

    Array
(
    [0] => 16711680
    [1] => 0
    [2] => 16777215
    [3] => 6618932
)

    See Also

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    User Contributed Notes 3 notes

    up
    2
    jbr at ya-right dot com
    18 years ago
    A few notes about this function...

    This function will only work on images where the palette is 256 colors or less. You also can not use imagetruecolortopalette() to reduce the palette on a true color PNG image that has greater than 256 colors in it's palette, then call this function. If you try to do this imagecolorexact() will report colors not being in the image when they are in the image!

    1. works on png(s) 8bit/256 colors or less.
    2. works on all gif(s)
    3. does not work on any type of jpg/jpeg image.
    up
    0
    samtobia at geemail dot com
    13 years ago
    A script that changes colors depending on get variable
    important to note: I had little success with pngs and getting true red
    gifs work much better

    <?php
    //0 is yellow, 1 is red, 2 is blue
    $y = 1 - ceil($_GET["c"]/2);
    $r = 1 - floor($_GET["c"]/2);
    $b = floor($_GET["c"]/2);

    $gd = imagecreatefromgif("example.gif");
    imagecolorset($gd, imagecolorexact($gd, 255, 0, 0), $r*255, $y*255, $b*255);
    imagecolorset($gd, imagecolorexact($gd, 191, 0, 0), $r*191, $y*191, $b*191);
    imagecolorset($gd, imagecolorexact($gd, 128, 0, 0), $r*128, $y*128, $b*128);
    imagecolorset($gd, imagecolorexact($gd, 255, 0, 0), $r*64, $y*64, $b*64);

    header('Content-Type: image/gif');
    imagegif($gd);

    ?>
    up
    -2
    info at educar dot pro dot br
    19 years ago
    <?php

    $src     = "../images/pic.gif";

    $red = 9;
    $green = 9;
    $blue = 4;

    $pic0026 = imagecreatefromgif ( $src );

    $ind = imagecolorexact ( $pic, $red, $green, $blue );

    echo     '<img src="../images/pic.gif" border="0" alt="pic" title="View pic" /><br /><br />';

    echo     "RED ( " . $red . " ) GREEN ( " . $green . " ) BLUE ( " . $blue . " )<br />-> Palette Index = " . $ind;

    if (     $ind != -1 )
    {
    echo     "<br />[ The color exists! ]";
    }
    else
    {
    echo     "<br />[ The color does not exist! ]";
    }

    imagedestroy ( $pic );

    ?>
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