'imagecolorat'和透明度 [英] 'imagecolorat' and transparency

问题描述

如何在图片

How it's possible to get the transparency value of a pixel on an image?

'imagecolorat'仅选取图像中指定位置的像素颜色的索引。使用该索引，我可以获得RGB值，但不能获得透明值。

'imagecolorat' picks only the index of the color of the pixel at the specified location in the image. With that index I can get the RGB values but not the transparent one.

希望您理解，并提前感谢您。

Hope you understand, and thank you in advance.

推荐答案

据我所知，透明度值由函数 imagecolorat 返回。你可以尝试：

As far as I know, the transparency value is returned by the function imagecolorat. Could you try:

$color        = imagecolorat($image, $x, $y);
$transparency = ($color >> 24) & 0x7F;

透明度是0到127之间的整数，所以我们需要屏蔽32位的前8位颜色整数。

The transparency is a integer between 0 and 127 so we need to mask the first 8 bits of the 32bit color integer.

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