imagejpeg function shows a long content - php

Question

I'm trying to write a code for making captcha images with GD in PHP. everything works fine but there is a problem that when I output the image with imagejpeg() function in addition to photos, it also shows some content including the strange Unicodes that I don't know what are they.
The file that the image is making in it (captcha.php):
<?php
$captcha_code=strtoupper(substr(sha1(random_bytes(64)),13,6));
$image = imagecreatetruecolor(200, 50);
imageantialias($image, true);
$colors = [];
$red = rand(125, 175);
$green = rand(125, 175);
$blue = rand(125, 175);
$black = imagecolorallocate($image, 30, 30, 30);
$white = imagecolorallocate($image, 230, 230, 230);
$textcolors = [$black, $white];
for($i = 0; $i < 5; $i++) {
$colors[] = imagecolorallocate($image, $red - 20*$i, $green - 20*$i, $blue - 20*$i);
}
imagefill($image, 0, 0, $colors[0]);
for($i = 0; $i < 10; $i++) {
imagesetthickness($image, rand(2, 10));
$rect_color = $colors[rand(1, 4)];
imagerectangle($image, rand(-10, 190), rand(-10, 10), rand(-10, 190), rand(40, 60), $rect_color);
}
$size = 24; $x = 5; $y = 30; $angle = 0; $quality = 100;
$color = imagecolorallocate($image, 255, 255, 255);
for($i = 0; $i < 6; $i++) {
$letter_space = 170/6;
$initial = 15;
imagettftext($image, 25, rand(-15, 15), $initial + $i*$letter_space, rand(20, 40), $textcolors[rand(0, 1)], __DIR__."\Acme.ttf", $captcha_code[$i]);
}
imagejpeg($image);
And in this part I try to show the image:
<div class="form-group col-6">
<label>Captcha Code</label>
<img src="scripts/captcha.php" alt="PHP Captcha">
</div>
The captcha image works fine but on the page that I try to show that there is a long content .
The content above the captcha image
I also tried to put header with image content type but another problem is that it causes just a black page with a small blank image in the middle of it although I don't have any errors.
I searched about this problem very much but I didn't find the exact way.
I'll be very happy if you help me :)