旋转的图像不会在PHP中显示

Question

So i am trying to create a compass to show wind direction.

 Function rotate($angle) {
     $original = imagecreatefrompng("img/Arrow.png");
     $compass = imagerotate($original, $angle, 0);
     return $compass;
 }

That will be displayed using some html that i am echoing. The variable angle is being passed from a database. The html on the php script looks like this:

<img src='".rotate($row['wind_dir'])."'/>

The image never displays, and clearly the browser does not know where it is.

When i view the html in my browser, the above line shows as

<img src="Resource id #4"/>

and when i click on it, it navigates to a 404.

What am i doing wrong? Have i forgotten a line in the image rotation function?

EDIT: Having tried some of the responses below, i get an image, but it only shows as a black box!

EDIT2:

Well after much fiddling, it turns out all that was needed was to the third value of imagerotate() to -1 as follows:

$original = imagecreatefrompng("img/goog.png");
$compass = imagerotate($original, $angle, -1);
imagealphablending($compass, true);
imagesavealpha($compass, true);
header('Content-Type: image/png');
imagepng($compass);
imagedestroy($compass);

Answer 1

You have to execute the function and send header: try like below, say our php file name is rotate.php :

rotate.php

function rotate($angle) {
     $original = imagecreatefrompng("test.png");
     $compass = imagerotate($original, $angle, 0);
     header('Content-Type: image/png');
     imagepng($compass);
     imagedestroy($compass);
 }

if(isset($_GET['angle'])){
 rotate($_GET['angle']);
}

THen in your html you can call the web resource i.e you php file as:

<img src="url_to_rotate.php?angle=90" />

Also remember to sanitize the GET input before executing it.