GD library arc smoothness - php

Question

I've tried the above code for creating arc with transparent white background, but it is always shown in distorted manner. Please help me how to make them smooth curved one's?
$im = imagecreatetruecolor(300, 300);
$backgroundColor = imagecolorallocatealpha($im, 255, 255, 255, 127);
imagefill($im, 0, 0, $backgroundColor);
$white = imagecolorallocate($im, 255,255,255);
imagecolortransparent($im, $white);
// Allocate A Color For The Text
$dark_blue = imagecolorallocate($im, 30, 65, 71);
imagesetthickness($im, 2);
//creation of thick arc
$thickness = 40;
for ($i = $thickness; $i > 0; $i--) {
imagearc($im, 150, 220, 180 - $i, 180 - $i, 180, 0, $dark_blue);
}

Answer 1

Increase the image size and the arc thickness, then gradually the arc smoothness keeps getting antialiased. I'm adding my code below for half ring/half donut image/half circle :
enter image description here
function scoreHalfDoughnutImage()
{
$score = 70;
$maxScore = 100;
$color = '#FC950C';
$imagePath = "doughnutContent2Image_".$score.".jpg";
// Create Image From Existing File
$im = imagecreatetruecolor(550, 340);// Create a 550x340 image
//imagealphablending($img,true);
$backgroundColor = imagecolorallocatealpha($im, 255, 255, 255, 127);//blending colors
imagefill($im, 0, 0, $backgroundColor);//creating white background
// Switch antialiasing on for one image
$white = imagecolorallocate($im, 255,255,255);
$black = imagecolorallocate($im, 0, 0, 0);
// for making transparent bg of white bg
imagecolortransparent($im, $white);
// Allocate A Color For The Text
$orange = imagecolorallocate($im, 252, 149, 12);
$dark_blue = imagecolorallocate($im, 30, 65, 71);
imagesetthickness($im, 4);
//creation of thick arc
$thickness = 40;
for ($i = $thickness; $i > 0; $i--) {
imagearc($im, 275, 273, (180 - $i)*3, (180 - $i)*3, 180, 0, $dark_blue);
imagearc($im, 275, 273, (180 - $i)*3, (180 - $i)*3, 180, 180+($score*1.8), $orange);
}
//imageantialias($im, true);
imagesetthickness($im, 1);
$text='NA';
// Setup the title on the center circle
if($score>=0)
$text=$score;
// Set Path to Font File
$font_path = 'lib/reports/MotivationEvaluation/font/arial.ttf';
// Print Text On Image
$textWidth = imagettfbbox(40, 0, $font_path, $text);
$x = 235;
if($textWidth[2] < 84)
{
$x = 250;
}
if($text!=='NA')
{
imagettftext($im, 45, 0, $x, 240, $dark_blue, $font_path, $text);
}
else
{
imagettftext($im, 35, 0, $x, 240, $dark_blue, $font_path, $text);
}
// Print Text On x-axis n y-axis
imagettftext($im, 32, 0, 25, 315, $dark_blue, $font_path, 0);
imagettftext($im, 32, 0, 25+450, 315, $dark_blue, $font_path, 100);
//imagealphablending($im, true); //not needed as we created the image
with alpha
imagesavealpha($im, true);
// Send Image to Browser
imagejpeg($im,$imagePath);
imagedestroy($im);
return $imagePath;
}