Example

function shadePixel($value, $r, $g, $b)
{
    $result = [];
    $result[] = intval($r * $value / 64);
    $result[] = intval($g * $value / 64);
    $result[] = intval($b * $value / 64);

    return $result;
}


function importImagePixels()
{
    $width = 320;
    $height = 200;
    //$imagick = new \Imagick();

    $imagick = new \Imagick();//;"magick:logo");


    for ($loop = 0; $loop<=255; $loop += 8) {
        $frame = new \Imagick();
        $frame->newPseudoImage($width, $height, "xc:black");
        //$frame->setImageFormat('gif');

        for ($y=0; $y<$height; $y++) {
            $pixels = [];
    
            for ($x = 0; $x < $width; $x++) {
                $pos = sqrt(($x * $x) + ($y * $y));
                $pos = (256 + $pos - $loop) % 256;
    
                if ($pos < 64) {
                    $rgbColor = shadePixel($pos, 255, 0, 0);
                }
                else if ($pos < 128) {
                    $rgbColor = shadePixel($pos - 64, 0, 255, 0);
                }
                else if ($pos < 192) {
                    $rgbColor = shadePixel($pos - 128, 0, 0, 255);
                }
                else {
                    $rgbColor = shadePixel($pos - 192, 255, 0, 255);
                }
    
                list($r, $g, $b) = $rgbColor;
                $pixels[] = $r;
                $pixels[] = $g;
                $pixels[] = $b;
            }
    
            $frame->importImagePixels(
                0, $y,
                320, 1,
                "RGB",
                \Imagick::PIXEL_CHAR,
                $pixels
            );
        }

        $imagick->addImage($frame);
        $imagick->setImageFormat('gif');
        $imagick->setImageDelay(3);
    }

    $imagick->setImageFormat('gif');
    $imagick->mergeImageLayers(\Imagick::LAYERMETHOD_OPTIMIZEIMAGE);
    header("Content-Type: image/gif");
    $imagick->setImageIterations(0);
    
    echo $imagick->getImagesBlob();

}