Set ImageMagick PNG image background color

Question

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?

I agree, see http://stackoverflow.com/questions/2569970/gd-converting-a-png-image-to-jpeg-and-making-the-alpha-by-default-white-and-not — AllisonC, May 23 '11 at 14:54
initially i tried to make jpg file... but i got a jpg with black background `:P` `:P` .. thats y i turned to png... do u know how to change jpg black background color?? or suggest me how to set one in png... — Alfred, May 23 '11 at 14:56
@AllisonC, I want to do it without GD. I first tried to make a jpg, but got one with black background. Do u know how to fix dat?? — Alfred, May 23 '11 at 15:05
i would try to draw a rectangle, same size as the image and fill it ... ? — helle, May 23 '11 at 16:33
I don't get it. I am no native english speaker. what means ny? what means bast? thanks — helle, May 23 '11 at 16:39

score 4 · Answer 1 · edited Nov 08 '12 at 16:48

4

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);

edited Nov 08 '12 at 16:48

Alessandro Minoccheri

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answered Nov 08 '12 at 16:30

TheTambu

121
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score 2 · Accepted Answer · answered May 25 '11 at 16:32

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)."' />";    
?>

Set ImageMagick PNG image background color

2 Answers2