设置ImageMagick PNG图像背景颜色

发布于 2024-11-09 15:46:54 字数 470 浏览 2 评论 0原文

我有一个 PHP 脚本来创建 PDF 文件的 PNG 缩略图，如下所示：

<?php
$file ="test.pdf";
$im = new imagick(realpath($file).'[0]');
$im->setImageFormat("png");
$im->resizeImage(200,200,1,0);
// start buffering
ob_start();
$thumbnail = $im->getImageBlob();
$contents =  ob_get_contents();
ob_end_clean();    
echo "<img src='data:image/jpg;base64,".base64_encode($thumbnail)."' />";    
?>

它返回缩略图，但背景是透明的。我想设置白色背景颜色（将 alpha 图层更改为白色）。我该怎么做？

原文

I have a PHP script to create a PNG thumbnail of a PDF file as follows:

<?php
$file ="test.pdf";
$im = new imagick(realpath($file).'[0]');
$im->setImageFormat("png");
$im->resizeImage(200,200,1,0);
// start buffering
ob_start();
$thumbnail = $im->getImageBlob();
$contents =  ob_get_contents();
ob_end_clean();    
echo "<img src='data:image/jpg;base64,".base64_encode($thumbnail)."' />";    
?>

Which returns a thumbnail, but the background is transparent. I want to set white background color (change the alpha layer to white). How can I do this?

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徒留西风 2024-11-16 15:46:54

解决方案不在于背景颜色，而在于 Alpha 通道！
尝试使用以下代码：

$im->readImage($fileInput);
$im->setImageAlphaChannel(imagick::ALPHACHANNEL_DEACTIVATE);

The solution is not in the background colour, but in the alpha channel!
Try with this code:

$im->readImage($fileInput);
$im->setImageAlphaChannel(imagick::ALPHACHANNEL_DEACTIVATE);

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〃温暖了心ぐ 2024-11-16 15:46:54

我正在做类似的事情，尽管我实际上是将图像写入磁盘 -
当我使用你的直接输出时，它起作用了，我从 PDF 中得到了实际的颜色。

经过一番调试，我发现问题实际上与

imagick::resizeImage()

功能有关。
无论出于何种原因，当您设置所有颜色、压缩等时，resizeImage 都会添加黑色背景。
我的解决方案是使用 GD 来调整大小，这样我就可以进行完整的动态调整大小 - 因为你对这样的事情不感兴趣，所以我会简单地使用图像采样功能。你的代码应该是这样的：

<?php
$file ="test.pdf";
$im = new imagick(realpath($file).'[0]');
$im->setCompression(Imagick::COMPRESSION_JPEG);
$im->setCompressionQuality(80);
$im->setImageFormat("jpeg");
$im->sampleImage(200,200);
// start buffering
ob_start();
$thumbnail = $im->getImageBlob();
$contents =  ob_get_contents();
ob_end_clean();    
echo "<img src='data:image/jpg;base64,".base64_encode($thumbnail)."' />";    
?>

I'm doing something similar, although I'm actually writing the image to the disk -
When I used your direct output, it worked and I got the actual color from the PDF.

Through a bit of debugging, I figured that the issue was actually related to the

imagick::resizeImage()

function.
For whatever reason, when you set all of your colors, compression, etc. the resizeImage adds the black background.
My solution is to use GD for the resizing, so that I can have a full dynamic resize - Since you're not interested in such thing, I would simply use the image sampling functionality. Your code should be like this:

<?php
$file ="test.pdf";
$im = new imagick(realpath($file).'[0]');
$im->setCompression(Imagick::COMPRESSION_JPEG);
$im->setCompressionQuality(80);
$im->setImageFormat("jpeg");
$im->sampleImage(200,200);
// start buffering
ob_start();
$thumbnail = $im->getImageBlob();
$contents =  ob_get_contents();
ob_end_clean();    
echo "<img src='data:image/jpg;base64,".base64_encode($thumbnail)."' />";    
?>

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