php 广东！将 png 图像转换为 jpeg 并默认将 alpha 设为白色而不是黑色
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GD! Converting a png image to jpeg and making the alpha by default white and not black
提问by Shawn
I tried something like this but it just makes the background of the image white, not necessarily the alpha of the image. I wanted to just upload everything as jpg's so if i could somehow "flatten" a png image with some transparently to default it to just be white so i can use it as a jpg instead. Appreciate any help. Thanks.
我试过这样的事情，但它只是使图像的背景变白，不一定是图像的 alpha。我只想将所有内容上传为 jpg，所以如果我能以某种方式“展平”带有一些透明的 png 图像以将其默认为白色，那么我可以将其用作 jpg。感谢任何帮助。谢谢。
$old = imagecreatefrompng($upload); $background = imagecolorallocate($old,255,255,255); imagefill($old, 0, 0, $background); imagealphablending($old, false); imagesavealpha($old, true);
回答by Alex Jasmin
<?php
$input_file = "test.png";
$output_file = "test.jpg";
$input = imagecreatefrompng($input_file);
list($width, $height) = getimagesize($input_file);
$output = imagecreatetruecolor($width, $height);
$white = imagecolorallocate($output, 255, 255, 255);
imagefilledrectangle($output, 0, 0, $width, $height, $white);
imagecopy($output, $input, 0, 0, 0, 0, $width, $height);
imagejpeg($output, $output_file);
