Merging two images via gradient

Question

I am trying to merge two images in PHP, overlapping each other in the middle like in here : https://i.sstatic.net/ejdDQ.jpg

However, I am having no luck. On the ImageMagick page, they are using this method to do it in the command line: http://www.imagemagick.org/Usage/photos/#overlap But since I cannot use exec on my server, I have to do it somehow with the help of the imagick extension installed on the server (https://www.php.net/manual/en/book.imagick.php).

Is there any way to make this work?

Answer 1

Using the source files from the link and the code below generates the image:

//Load the images
$left = new Imagick(realpath('../images/im/holocaust_tn.gif'));
$right = new Imagick(realpath('../images/im/spiral_stairs_tn.gif'));
$gradient = new Imagick(realpath('../images/im/overlap_mask.png'));

//The right bit will be offset by a certain amount - avoid recalculating.
$offsetX = $gradient->getImageWidth() - $right->getImageWidth();


//When doing the fading of the images, ImageMagick uses "White == show image".
//The gradient is setup with black on the left, white on the right. So the for
//the left image we need to reverse the gradient to make it white on the left.
$negativeGradient = clone $gradient;
$negativeGradient->negateimage(false);

//Fade out the left part
$left->compositeimage(
    $negativeGradient,
    Imagick::COMPOSITE_COPYOPACITY,
    0, 0
);

//Fade out the right part - offset the gradient
//to make it align in the final image
$right->compositeimage(
    $gradient,
    Imagick::COMPOSITE_COPYOPACITY,
    -$offsetX, 0
);

//Create a new canvas to render everything in to.
$canvas = new Imagick();
$canvas->newImage($gradient->getImageWidth(), $gradient->getImageHeight(), new ImagickPixel('black'));

//Blend left half into final image
$canvas->compositeimage(
    $left,
    Imagick::COMPOSITE_BLEND,
    0, 0
);

//Blend Right half into final image
$canvas->compositeimage(
    $right,
    Imagick::COMPOSITE_BLEND,
    $offsetX, 0
);


//Output the final image
$canvas->setImageFormat('png');

header("Content-Type: image/png");
echo $canvas->getImageBlob();
// And Robert is your father's brother.