This is a more complicated example of how to cross fade a row of images with smooth transitions between each image.

It creates the gradients for blending as required, which allows the transition between the images to be controlled.

Contrast
Blend midpoint
This is a more complicated example of how to cross fade a row of images with smooth transitions between each image.

It creates the gradients for blending as required, which allows the transition between the images to be controlled.
function generateBlendImage($height, $overlap, $contrast = 10, $midpoint = 0.5)
{
    $imagick = new \Imagick();
    $imagick->newPseudoImage($height, $overlap, 'gradient:black-white');
    $quantum = $imagick->getQuantum();
    $imagick->sigmoidalContrastImage(true, $contrast, $midpoint * $quantum);

    return $imagick;
}


function mergeImages(
    array $srcImages,
    $outputSize,
    $overlap,
    $contrast = 10,
    $blendMidpoint = 0.5,
    $horizontal = true
) {

    $images = array();
    $newImageWidth = 0;
    $newImageHeight = 0;

    if ($horizontal == true) {
        $resizeWidth = 0;
        $resizeHeight = $outputSize;
    }
    else {
        $resizeWidth = $outputSize;
        $resizeHeight = 0;
    }

    $blendWidth = 0;

    foreach ($srcImages as $srcImage) {
        $nextImage = new \Imagick(realpath($srcImage));
        $nextImage->resizeImage($resizeWidth, $resizeHeight, \Imagick::FILTER_LANCZOS, 0.5);

        if ($horizontal == true) {
            $newImageWidth += $nextImage->getImageWidth();
            $blendWidth = $nextImage->getImageHeight();
        }
        else {
            //$newImageWidth = $nextImage->getImageWidth();
            $blendWidth = $nextImage->getImageWidth();
            $newImageHeight += $nextImage->getImageHeight();
        }

        $images[] = $nextImage;
    }

    if ($horizontal == true) {
        $newImageWidth -= $overlap * (count($srcImages) - 1);
        $newImageHeight = $outputSize;
    }
    else {
        $newImageWidth = $outputSize;
        $newImageHeight -= $overlap * (count($srcImages) - 1);
    }

    if ($blendWidth == 0) {
        throw new \Exception("Failed to read source images");
    }

    $fadeLeftSide = generateBlendImage($blendWidth, $overlap, $contrast, $blendMidpoint);

    if ($horizontal == true) {
        //We are placing the images horizontally.
        $fadeLeftSide->rotateImage('black', -90);
    }

    //Fade out the left part - need to negate the mask to
    //make math correct
    $fadeRightSide = clone $fadeLeftSide;
    $fadeRightSide->negateimage(false);

    //Create a new canvas to render everything in to.
    $canvas = new \Imagick();
    $canvas->newImage($newImageWidth, $newImageHeight, new \ImagickPixel('black'));

    $count = 0;

    $imagePositionX = 0;
    $imagePositionY = 0;

    /** @var $image \Imagick */
    foreach ($images as $image) {
        $finalBlending = new \Imagick();
        $finalBlending->newImage($image->getImageWidth(), $image->getImageHeight(), 'white');

        if ($count != 0) {
            $finalBlending->compositeImage($fadeLeftSide, \Imagick::COMPOSITE_ATOP, 0, 0);
        }

        $offsetX = 0;
        $offsetY = 0;

        if ($horizontal == true) {
            $offsetX = $image->getImageWidth() - $overlap;
        }
        else {
            $offsetY = $image->getImageHeight() - $overlap;
        }

        if ($count != count($images) - 1) {
            $finalBlending->compositeImage($fadeRightSide, \Imagick::COMPOSITE_ATOP, $offsetX, $offsetY);
        }

        $image->compositeImage($finalBlending, \Imagick::COMPOSITE_COPYOPACITY, 0, 0);
        $canvas->compositeimage($image, \Imagick::COMPOSITE_BLEND, $imagePositionX, $imagePositionY);

        if ($horizontal == true) {
            $imagePositionX = $imagePositionX + $image->getImageWidth() - $overlap;
        }
        else {
            $imagePositionY = $imagePositionY + $image->getImageHeight() - $overlap;
        }
        $count++;
    }

    return $canvas;
}

function imagickCompositeGen($contrast = 10, $blendMidpoint = 0.5)
{
    $size = 160;

    //Load the images
    $output = mergeImages(
        [
            'images/lories/6E6F9109_480.jpg',
            'images/lories/IMG_1599_480.jpg',
            'images/lories/IMG_2561_480.jpg',
            'images/lories/IMG_2837_480.jpg',
            //'images/lories/IMG_4023.jpg',
        ],
        $size,
        0.2 * $size, //overlap
        $contrast,
        $blendMidpoint,
        true
    );

    //$output = generateBlendImage(200, 200, 5, 0.5);
    $output->setImageFormat('png');

    header("Content-Type: image/png");
    echo $output->getImageBlob();
}