Solution to the value of the verification code coordinate

About the verification code coordinate value --------------------------------------------- code ------------------------------------------------- $ image_width = 70; // set the image width about the verification code coordinate value
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$ Image_width = 70; // set the image width
$ Image_height = 18; // set the image height

$ New_number = 1234;
$ Num_image = imagecreate ($ image_width, $ image_height); // Create a canvas
Imagecolorallocate ($ num_image, 255,255,255); // you can specify the canvas color.

For ($ I = 0; $ I $ Font = mt_rand (); // set a random font.
$ X = mt_rand () + $ image_width * $ I/4; // Set the X coordinate of the random character location
$ Y = mt_rand (1, $ image_height/4); // you can specify the Y coordinate of the random character location.
$ Color = imagecolorallocate ($ num_image, mt_rand (0,100), mt_rand (0,150), mt_rand (0,200); // set the character color
Imagestring ($ num_image, $ font, $ x, $ y, $ new_number [$ I], $ color); // horizontal output character
}

Imagepng ($ num_image); // generate an image in PNG format
Imagedestroy ($ num_image); // release image resources
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$ X = mt_rand () + $ image_width * $ I/4; // Set the X coordinate of the random character location
$ Y = mt_rand (1, $ image_height/4); // you can specify the Y coordinate of the random character location.

Why does $ x and $ y take this value? Is it random or regular? Please explain the rule.




------ Solution --------------------
This location can be obtained at will
However, in theory, we believe that the character of the verification code cannot exceed the line, otherwise it will not be recognized.
Generally, the location of the verification code should be random, and the random range should be maximized without exceeding the edge.
This reduces the chance of being cracked by machine scripts.