PHP imagick COMPOSITE_DSTIN result has black background - php

Question

I try to set a text gradient from this solution here https://www.sitepoint.com/community/t/gd-text-gradient/82127/9
But the background color of the final image is black, I try $im->flattenImages and $img->setBackgroundColor but it's not working.
$im = new Imagick();
$draw = new ImagickDraw();
$draw->setFontSize(90);
$draw->setFillColor(new ImagickPixel("black"));
$draw->setTextEncoding('UTF-8');
$draw->setGravity(Imagick::GRAVITY_CENTER);
$metric = $im->queryFontMetrics($draw, $text);
$width = $metric['textWidth'];
$height = $metric['textHeight'];
/* Create and save the gradiant */
$Imagick = new Imagick();
$Imagick->newPseudoImage($height, $width, "gradient:#FB7F4C-#FF409C");
/*** rotate the image ***/
$Imagick->rotateImage(new ImagickPixel(), 270);
$Imagick->setImageFormat('png');
$Imagick->writeImage("gradiant.png");
/* Create and save the canvas */
$im->newPseudoImage($width, $height, "null:");
$im->setImageFormat('png');
$im->writeImage("canvas.png");
/* Add the text to the canvas ( Make the mask )*/
$im = new Imagick("canvas.png");
// Write the text on the image
$im->annotateImage($draw, 0, 0, 0, $text);
$im->setImageBackgroundColor("transparent"); // <= Here
/* Final image */
$canvas = new Imagick("gradiant.png");
$canvas->compositeImage($im, imagick::COMPOSITE_DSTIN, 0, 0, Imagick::CHANNEL_ALPHA);
$canvas->setImageFormat('png');
$canvas->writeImage(__DIR__ . "/../../final.png");
header('Content-Type: image/' . $im->getImageFormat());
echo $canvas;
unlink("canvas.png");
unlink("gradiant.png");
I found after the COMPOSITE_DSTIN the background color goes black, I try many way but its not working
How to remove black background?

Answer 1

I'm solved it by adding alphachannel
I try $canvas->setImageAlphaChannel(Imagick::ALPHACHANNEL_RESET); and after that the background stay transparent
UPDATE
After I updated my imagick library it's stop working and search for similar issue and found this Imagemagick compose image inverted
And here the code that works well
$canvas->transformImageColorspace(Imagick::COLORSPACE_SRGB);