在 PHP 中将 JPG/GIF 图像转换为 PNG？
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Convert JPG/GIF image to PNG in PHP?
提问by Aaron
Possible Duplicate of
Convert jpg image to gif, png & bmp format using PHP
I have a PHP form that allows image uploads and checks exif_imagetype();to make sure an image is valid.
我有一个 PHP 表单，它允许上传图像并检查exif_imagetype();以确保图像有效。
However, I want all formats, PNG, JPG, JPEG, and GIF, to end up being PNG once submitted.
但是，我希望所有格式（PNG、JPG、JPEG 和 GIF）在提交后最终成为 PNG。
How can I go about doing this?
我该怎么做呢？
回答by mario
You just need imagepng()then. In fact it almost becomes a one-liner:
你只需要imagepng()那时。事实上，它几乎变成了单行：
imagepng(imagecreatefromstring(file_get_contents($filename)), "output.png");
You would use $_FILES["id"]["tmp_name"]for the filename, and a different output filename obviously. But the image format probing itself would become redundant.
$_FILES["id"]["tmp_name"]显然，您将使用文件名和不同的输出文件名。但是图像格式探测本身将变得多余。
回答by Cyclonecode
Based on what kind of image it is you could select the correct function to open the file:
根据它是什么类型的图像，您可以选择正确的函数来打开文件：
$extension = strtolower(pathinfo($filename, PATHINFO_EXTENSION));
switch ($extension) {
case 'jpg':
case 'jpeg':
$image = imagecreatefromjpeg($filename);
break;
case 'gif':
$image = imagecreatefromgif($filename);
break;
case 'png':
$image = imagecreatefrompng($filename);
break;
}
Then you just save the file using:
然后您只需使用以下命令保存文件：
imagepng($image, $new_filename, $quality);
回答by Zulkhaery Basrul
<form method="post" enctype="multipart/form-data">
<input type="file" name="image" />
<input type="submit" name="submit" value="Submit" />
</form>
<?php
if(isset($_POST['submit']))
{
if(exif_imagetype($_FILES['image']['tmp_name']) == IMAGETYPE_GIF)
{
$newpng = 'image.png';
$png = imagepng(imagecreatefromgif($_FILES['image']['tmp_name']), $newpng);
}
elseif(exif_imagetype($_FILES['image']['tmp_name']) == IMAGETYPE_JPEG)
{
$newpng = 'image.png';
$png = imagepng(imagecreatefromjpeg($_FILES['image']['tmp_name']), $newpng);
}
else //already png
{
$newpng = 'image.png';
}
}
?>
回答by deceze
Very simple using the gd functions:
使用gd 函数非常简单：
switch (exif_imagetype($image)) {
case IMAGETYPE_GIF :
$img = imagecreatefromgif($image);
break;
case IMAGETYPE_JPEG :
$img = imagecreatefromjpeg($image);
break;
default :
throw new InvalidArgumentException('Invalid image type');
}
imagepng($img, $filename);
For conciseness this obviously doesn't handle the case if the image is already a PNG.
为简洁起见，如果图像已经是 PNG，这显然不能处理这种情况。
