AgjGd::imageblendedcolorallocate Example: Alpha

A fully opaque black is blended with a half-transparent black to show that the alpha channel is averaged along with the red, green and blue channels. The middle rectangle is the result, sitting halfway between the two rectangles either side of it.

Source Code: examples/imageblendedcolorallocate/02-alpha.php

<?php

/**
 * AgjGd Example (imageblendedcolorallocate: Alpha)
 *
 * Copyright (c) 2018–2026 Andrew G. Johnson <andrew@andrewgjohnson.com>
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * PHP version 8
 *
 * @category  AndrewGJohnson
 * @package   AgjGd
 * @author    Andrew G. Johnson <andrew@andrewgjohnson.com>
 * @copyright 2018–2026 Andrew G. Johnson <andrew@andrewgjohnson.com>
 * @license   https://opensource.org/licenses/mit/ The MIT License
 * @link      https://github.com/andrewgjohnson/AgjGd
 */

use AndrewGJohnson\AgjGd;

// Load the AgjGd class directly from source, or fall back to the Composer autoloader
if (file_exists('../../source/AndrewGJohnson/AgjGd.php')) {
    require_once '../../source/AndrewGJohnson/AgjGd.php';
} elseif (file_exists('../../vendor/autoload.php')) {
    require_once '../../vendor/autoload.php';
} elseif (!class_exists('AndrewGJohnson\AgjGd')) {
    die('AndrewGJohnson\AgjGd class not found');
}

// Set the parameters for our image
$width           = 600;
$height          = 300;
$offset          = (int)round($width / 10);
$rectangleWidth  = $offset * 2;
$rectangleHeight = $height - ($offset * 2);

// Create our image
$im = imagecreatetruecolor($width, $height);

if ($im === false) {
    die('Could not create the image');
}

// Set our image’s colors, blending an opaque black with a translucent black
$backgroundColor  = (int)imagecolorallocate($im, 0xEE, 0xEE, 0xEE);
$opaqueBlack      = (int)imagecolorallocatealpha($im, 0x00, 0x00, 0x00, 0);
$translucentBlack = (int)imagecolorallocatealpha($im, 0x00, 0x00, 0x00, 63);
$blendedBlack     = (int)AgjGd::imageblendedcolorallocate($im, $opaqueBlack, $translucentBlack);

// Fill our image with the background color
imagefill($im, 0, 0, $backgroundColor);

// Fill our image with both colors and the new blended color
imagefilledrectangle(
    $im,
    $offset,
    $offset,
    $offset + $rectangleWidth,
    $offset + $rectangleHeight,
    $opaqueBlack
);

imagefilledrectangle(
    $im,
    ($offset * 2) + $rectangleWidth,
    $offset,
    ($offset + $rectangleWidth) * 2,
    $offset + $rectangleHeight,
    $blendedBlack
);

imagefilledrectangle(
    $im,
    ($offset * 3) + ($rectangleWidth * 2),
    $offset,
    ($offset + $rectangleWidth) * 3,
    $offset + $rectangleHeight,
    $translucentBlack
);

// Display our image
header('Content-Type: image/png');
imagepng($im);

Expected Output: examples/imageblendedcolorallocate/02-alpha.png