使用 PHP 实现 GD 库中的 imagepng() 和透明度
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imagepng() and transparency in GD library with PHP
提问by Strawberry
When using the function imagepng()in PHP, how can I make sure the images that I save are saved with a transparent background?
imagepng()在 PHP 中使用该函数时，如何确保我保存的图像以透明背景保存？
采纳答案by Eric
Here is an example of the imagecolortransparentfunction (if it helps):
这是该imagecolortransparent功能的示例（如果有帮助）：
<?php
// Create a 55x30 image
$im = imagecreatetruecolor(55, 30);
$red = imagecolorallocate($im, 255, 0, 0);
$black = imagecolorallocate($im, 0, 0, 0);
// Make the background transparent
imagecolortransparent($im, $black);
// Draw a red rectangle
imagefilledrectangle($im, 4, 4, 50, 25, $red);
// Save the image
imagepng($im, './imagecolortransparent.png');
imagedestroy($im);
?>
回答by mauris
Simply do this:
只需这样做：
imagealphablending($img, false);
imagesavealpha($img, true);
Before outputting. Make sure that all source files (if you used any) are set to PNG 32-bit with transparency - if not the output may differ with black background or transparency does not comply.
输出前。确保所有源文件（如果您使用过）都设置为具有透明度的 PNG 32 位 - 如果不是，则输出可能与黑色背景不同或透明度不符合要求。
回答by user2731504
Here is the example
这是例子
$newimage = imagecreatetruecolor($dst_w, $dst_h);
imagealphablending($newimage, false);
imagesavealpha($newimage, true);
$transparentindex = imagecolorallocatealpha($newimage, 255, 255, 255, 127);
imagefill($newimage, 0, 0, $transparentindex);
回答by lamelas
There's a function called imagecolortransparentthat allows you to set which color is made transparent. I don't know if this answers your question.
有一个名为imagecolortransparent的函数，它允许您设置透明的颜色。我不知道这是否回答了你的问题。
