Convert PNG to JPG and set transparent background to white with ImageMagick and PHP

Question

How can I use ImageMagick (with the php extension) to set the transparent background to white when converting an image from PNG to JPEG?

Answer 1

At time of writing, you have not specified which extension you are using, but if you were using the commandline, the command would be:

convert image.png -background white -flatten -alpha off image.jpg

More information can be found on the Masking Usage documentation.

Using IMagick for instance, I think you could do this as follows:

(totally untested, never used IMagick and don't have it installed to test)

$image = new IMagick('image.png');

$flattened = new IMagick();
$flattened->newImage($image->getImageWidth(), $image->getImageHeight(), new ImagickPixel("white"));

$flattened->compositeImage($image, imagick::COMPOSITE_OVER, 0, 0);

$flattened->setImageFormat("jpg");
$flattened->writeImage('image.jpg');

$image->clear();
$image->destroy();
$flattened->clear();
$flattened->destroy();

Answer 2

If you are using the Imagick extension:

<?php
// load the source transparent png
$i = new IMagick('image.png');

// set the background to white
// you can also use 'rgb(255,255,255)' in place of 'white'
$i->setImageBackgroundColor(new ImagickPixel('white'));

// flattens multiple layers
$i = $i->flattenImages();

// the output format
$i->setImageFormat('jpg');

// save to disk
$i->writeImage('image.jpg');

// and/or output directly
// header('Content-Type: '.$i->getFormat());
// echo $i->getImageBlob();

// cleanup
$i->clear();
$i->destroy();