PHP中的imagecolortransparent无法正常工作 [英] imagecolortransparent in PHP not working
问题描述
我想更改图片中的白色（ http：/ /www.arso.gov.si/vreme/napovedi%20in%20podatki/radar.gif ）透明。我认为代码看起来正确，没有错误日志，但图片保持不变。我仔细检查图像中的颜色是否真的是白色而且是。请帮忙。
I want to change white color in image (http://www.arso.gov.si/vreme/napovedi%20in%20podatki/radar.gif) to transparent. I think that code looks right, there is no error logs but picture stays unchanged. I double checked if color in image is really white and it is. Please help.
<?php
$im = imagecreatefromgif("http://www.arso.gov.si/vreme/napovedi%20in%20podatki/radar.gif");
imagealphablending($im, false);
imagesavealpha($im, true);
$white = imagecolorallocate($im, 255, 255, 255);
imagecolortransparent($im, $white);
imagegif($im, './image_radar_tran.gif');
imagedestroy($im);
?>
<body style="background-color: lightgoldenrodyellow;">
<img src="./image_radar_tran.gif" />
</body>
推荐答案
更改：
$white = imagecolorallocate($im, 255, 255, 255);
收件人：
$white = imagecolorexact($im, 255, 255, 255);
它会起作用。原因是颜色'white'已在您使用的gif的索引中定义，因此您无法为该颜色分配新索引。相反，使用 imagecolorexact ，您将获得要使用的白色的现有索引，然后可以将其更改为透明。
And it will work. The reason is that the color 'white' is already defined in the index of the gif you are using, so you can't allocate a new index for that color. Instead, using imagecolorexact, you get the existing index for the white color to use and can then change it to transparent.
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![http：/ /www.arso.gov.si/vreme/napovedi%20in%20podatki/radar.gif](\"http://www.arso.gov.si/vreme/napovedi%20in%20podatki/radar.gif\"){kind=link}