如何在PHP中的图像上绘制一条垂直线[重复]

i am making an antibot that displays different pictures, and asks the user to click on a specific picture. However, i would like some small random change to be made to the picture each time, so that software could not analyze and determine which picture is beeing displayed...

I would like one horizontal and one vertical line to be added at random coordinates with random color to the picture each time, then display the picture using get_file_contents and header.

Hope this makes sense... I would not want the changes to be saved to the picture, but only displayed to the user... I am using file_get_contents and header to display the picture, like this:

$id = $_GET['id'];
$image = "images/".$id . ".jpg";
$content = file_get_contents($image); 
header('Content-Type: image/jpeg');
echo $content;
exit()

Thanks...

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Using GD within PHP would allow you to do this

http://php.net/manual/en/book.image.php

create a file called image.php

From the php manual:

<?php

header("Content-type: image/png");
$string = $_GET['text'];
$im     = imagecreatefrompng("images/button1.png");
$orange = imagecolorallocate($im, 220, 210, 60);
$px     = (imagesx($im) - 7.5 * strlen($string)) / 2;
imagestring($im, 3, $px, 9, $string, $orange);
imagepng($im);
imagedestroy($im);

?>

You could add a line by using the imageline function

<?php

header("Content-type: image/png");
$string = $_GET['text'];
$im     = imagecreatefrompng("images/button1.png");
$orange = imagecolorallocate($im, 220, 210, 60);
$px     = (imagesx($im) - 7.5 * strlen($string)) / 2;
imagestring($im, 3, $px, 9, $string, $orange);
imageline($im, $x1, $y1, $x2, $y2, $orange);
imagepng($im);
imagedestroy($im);

?>

There are so many PHP GD functions available to achive this I think below code snippet may help you

<?php

$im = imagecreatefrompng("images/yourImage.png");
$white = imagecolorallocate($im, 0xFF, 0xFF, 0xFF);

// Draw a vertical dashed line
imagedashedline($im, 50, 25, 50, 75, $white);

// Save the image
imagepng($im, './imagewithdashedline.png');
imagedestroy($im);
?>

reference PHP GD imagedashedline function