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    imagecolorexact

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

    imagecolorexact — 取得指定颜色的索引值

    说明

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

    返回图像调色板中指定颜色的索引值。

    如果图象由文件创建，只有该图象使用到的颜色会被解析。仅存在于调色板中的颜色不会被解析。

    参数

    image

    由图象创建函数(例如imagecreatetruecolor())返回的 GdImage 对象。

    red

    红色成分的值。

    green

    绿色成分的值。

    blue

    蓝色成分的值。

    返回值

    返回调色板中指定颜色的索引值，如果该颜色不存在则返回 -1。

    更新日志

    版本 说明
    8.0.0 image 现在需要 GdImage 实例；之前需要有效的 gd resource。

    示例

    示例 #1 从 GD logo 中获取颜色

    <?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);
    ?>

    以上示例的输出类似于：

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

    参见

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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
    1
    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
    0
    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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