Problems with bilinear distortion

IMagick is a native PHP extension to create and modify images using the ImageMagick API. ImageMagick Studio LLC did not write nor does it maintain the IMagick extension, however, IMagick users are welcome to discuss the extension here.
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Problems with bilinear distortion

Post by eriqjaffe »

I'm running into some issues with bilinear distortion corrupting an image. The image is being created on an HTML5 canvas that I'm posting to a PHP script. The expected result should look like this:


...but my production server is giving me this:


The code that works on my development system is as follows:

Code: Select all

header('Content-type: image/png');
header('Content-Disposition: attachment; filename="test.png"');

$deformation = $_POST['deform'];
$amount = $_POST['amount'];
$encoded = $_POST['imgdata'];
$encoded = str_replace(' ', '+', $encoded);
$decoded = base64_decode($encoded);

echo $deformation($decoded,40);

function skewUp($image,$amount) {
	$im = new Imagick();
	$im->setBackgroundColor(new ImagickPixel('transparent'));
	$im->setImageVirtualPixelMethod( imagick::VIRTUALPIXELMETHOD_BACKGROUND );
	$im->setImagePage(0, 0, 0, 0);
	$x1 = $im->getImageWidth();
	$x2 = $im->getImageWidth();
	$y1 = $im->getImageHeight();
	$y2 = $im->getImageHeight()/((100-$amount)*0.01);
	$im->extentImage ($x2,$y2,0,0);
	$points = array(
		0, 0, 0, $im->getImageHeight()-$y1, #top left
		0, $y1, 0, $y2, #bottom left
		$x1, 0, $x1, 0, #top right
		$x1, $y1, $x1, $y1 #bottom right

	$im->distortImage( Imagick::DISTORTION_BILINEAR, $points, TRUE );
	$im->setImagePage(0, 0, 0, 0);
One thing that could be the cause is that my development box is not an exact mirror of my production server - the dev server is running PHP 5.5.9 with imagick 6.7.7-10 while the production server is running PHP 5.4.43 with imagick 6.5.4-7. Maybe there's just something I need to do differently on the production box, but I can't figure out what. Any assistance would be appreciated.