(PHP 4 >= 4.0.6, PHP 5, PHP 7)
imagecolorclosestalpha — 取得与指定的颜色加透明度最接近的颜色
$image
, int $red
, int $green
, int $blue
, int $alpha
) : int
返回图像调色板中与指定的 RGB 值以及
alpha 深度最"接近"的颜色。
image由图象创建函数(例如imagecreatetruecolor())返回的图象资源。
red红色成分的值。
green绿色成分的值。
blue蓝色成分的值。
alphaA value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.
Returns the index of the closest color in the palette.
Example #1 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)
$colors = array(
array(254, 145, 154, 50),
array(153, 145, 188, 127),
array(153, 90, 145, 0),
array(255, 137, 92, 84)
);
// Loop through each search and find the closest color in the palette.
// Return the search number, the search RGB and the converted RGB match
foreach($colors as $id => $rgb)
{
$result = imagecolorclosestalpha($im, $rgb[0], $rgb[1], $rgb[2], $rgb[3]);
$result = imagecolorsforindex($im, $result);
$result = "({$result['red']}, {$result['green']}, {$result['blue']}, {$result['alpha']})";
echo "#$id: Search ($rgb[0], $rgb[1], $rgb[2], $rgb[3]); Closest match: $result.\n";
}
imagedestroy($im);
?>
以上例程的输出类似于：
#0: Search (254, 145, 154, 50); Closest match: (252, 150, 148, 0). #1: Search (153, 145, 188, 127); Closest match: (148, 150, 196, 0). #2: Search (153, 90, 145, 0); Closest match: (148, 90, 156, 0). #3: Search (255, 137, 92, 84); Closest match: (252, 150, 92, 0).
Note: 此函数需要 GD 2.0.1 或更高版本(推荐 2.0.28 及更高版本)。