How to draw a partial arc and fill it using imagefilledarc() function in PHP?

The imagefilledarc() function is a built-in PHP function used to draw and fill a partial arc. This function requires the GD extension and is commonly used for creating pie charts, progress indicators, and other graphical elements.

Note: To use imagefilledarc(), you need the GD extension enabled in PHP. Install it using: sudo apt-get install php-gd on Ubuntu/Debian or enable it in php.ini on Windows.

Syntax

bool imagefilledarc($image, $cx, $cy, $width, $height, $start, $end, $color, $style)

Parameters

The imagefilledarc() function takes nine parameters −

• $image − Image resource created by imagecreate() or imagecreatetruecolor()

• $cx − X-coordinate of the arc center

• $cy − Y-coordinate of the arc center

• $width − Arc width in pixels

• $height − Arc height in pixels

• $start − Start angle in degrees (0° is at 3 o'clock position)

• $end − End angle in degrees (drawn clockwise)

• $color − Color identifier created with imagecolorallocate()

• $style − Drawing style, can be one of the following −

  • IMG_ARC_PIE − Creates a pie slice with rounded edges

  • IMG_ARC_CHORD − Connects start and end points with a straight line

  • IMG_ARC_NOFILL − Draws outline only, no fill

  • IMG_ARC_EDGED − Connects start/end angles to center (used with NOFILL)

Return Value

Returns true on success or false on failure.

Example 1: Basic Pie Arc

This example creates a simple pie arc with a gray border −

<?php
    define("WIDTH", 700);
    define("HEIGHT", 550);

    // Create the image
    $image = imagecreate(WIDTH, HEIGHT);

    // Allocate colors
    $bg = $white = imagecolorallocate($image, 0x00, 0x00, 0x80);
    $gray = imagecolorallocate($image, 122, 122, 122);

    // Create pie arc
    $center_x = (int)WIDTH/2;
    $center_y = (int)HEIGHT/2;
    imagerectangle($image, 0, 0, WIDTH-2, HEIGHT-2, $gray);
    imagefilledarc($image, $center_x, $center_y, WIDTH/2, HEIGHT/2, 0, 220, $gray, IMG_ARC_PIE);

    // Output image
    header("Content-Type: image/png");
    imagepng($image);
    imagedestroy($image);
?>

Example 2: 3D Effect Arc

This example demonstrates creating a 3D-style arc using multiple layers −

<?php
    // Create image
    $image = imagecreatetruecolor(700, 300);
    
    // Allocate colors
    $darkgray = imagecolorallocate($image, 0x90, 0x90, 0x90);
    $darkred = imagecolorallocate($image, 0x90, 0x00, 0x00);

    // Create 3D effect by drawing multiple layers
    for ($i = 60; $i > 50; $i--) {
        imagefilledarc($image, 100, $i, 200, 100, 75, 360, $darkred, IMG_ARC_PIE);
    }
    imagefilledarc($image, 100, $i, 200, 100, 45, 75, $darkgray, IMG_ARC_PIE);

    // Output image
    header('Content-type: image/png');
    imagepng($image);
    imagedestroy($image);
?>

Arc Style Comparison

Conclusion

The imagefilledarc() function is powerful for creating graphical elements like pie charts and progress indicators. Remember that angles are measured clockwise from the 3 o'clock position, and always call imagedestroy() to free memory after image processing.