Gmagick::scaleimage

Its important to understand that the boolean flag : $FIT is used as a MAXIMUM boundary of either X or Y

If you use a physical image with a size of 128x256
 
 scaleImage(200, 100, true);  Will scale Y to 100 and X will be calculated
 scaleImage(100, 120, true);  Will scale X to 100 and Y will be calculated

$FIT is a LIMITER which is why it requires both an X and a Y for $FIT=true

CORRECTION

Replace

echo 'img src="data:image/jpeg:base64,'.base64_encode($image).'">';

With 

echo '<img src="data:image/jpeg:base64,'.base64_encode($image).'">';

Simple method to load an image from file, resize and display without writing to disk.
tested on jpg, gif and bmp
<?php
$image= new Gmagick( "yourimage.jpg");
$image->scaleimage(300,0);
echo 'img src="data:image/jpeg:base64,'.base64_encode($image).'">';
$image->destroy();
?>