PHP GD:需要找出alpha数量
想象一下。我有一个彩色像素(255,0,0)[红色]。没有人在上面画上带有*alpha的白色。我知道背景色,我知道它是用什么颜色涂的,我需要得到涂过的颜色的alpha值。怎么做 到目前为止,我们已经:PHP GD:需要找出alpha数量,php,colors,gd,rgb,alpha,Php,Colors,Gd,Rgb,Alpha,想象一下。我有一个彩色像素(255,0,0)[红色]。没有人在上面画上带有*alpha的白色。我知道背景色,我知道它是用什么颜色涂的,我需要得到涂过的颜色的alpha值。怎么做 到目前为止,我们已经: $im = imagecreatefrompng('public/images/bg-tmp.png'); // we need to find a nearest match for this array in every pixel /*$colors = array( array(
$im = imagecreatefrompng('public/images/bg-tmp.png');
// we need to find a nearest match for this array in every pixel
/*$colors = array(
array(255, 255, 255, 100),
array(255, 255, 255, 75),
array(255, 255, 255, 50),
array(255, 255, 255, 25),
array(255, 255, 255, 0),
);*/
// finding out the pixel color
$rgb = imagecolorat($im, 0, 6);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
var_dump($r, $g, $b);
嗯。所以我取得了进步
$im = imagecreatefrompng('public/images/bg-tmp.png');
$pixels = array();
for($y = 0; $y < 24; $y++)
{
for($x = 0; $x < 24; $x++)
{
$rgb = imagecolorat($im, $x, $y);
此代码将为您提供一个很好的结果。然而,这还不够好。请提出改进建议。答案如下:
function calc_alpha_diff($R1,$G1,$B1,$R2,$G2,$B2)
{
$color_diff = max($R1,$R2) - min($R1,$R2) + max($G1,$G2) - min($G1,$G2) + max($B1,$B2) - min($B1,$B2);
$array = array
(
100 => 510, // 1
75 => 382, // 0.75
50 => 256, // 0.5
25 => 128, // 0.25
0 => 0 // 0
);
// find the nearest value
foreach($array as $key => $val)
{
$delta = abs($val - $color_diff);
if(!isset($min_delta) || $min_delta > $delta)
{
$min_delta = $delta;
$alpha = $key;
}
}
return $alpha;
}
$im = imagecreatetruecolor(24, 24);
foreach($pixels as $p)
{
if($p[2] != 0)
{
imagesetpixel($im, $p[0], $p[1], imagecolorallocatealpha($im, 255, 0, 0, $p[2]));
}
}
// make image transperant
imagecolortransparent($im, 0);
imagepng($im);
imagedestroy($im);
header('Content-type: image/png');
exit;