<?php

/**
 * Imageblendedcolorallocate v1.1.1
 *
 * 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 5
 *
 * @category  Andrewgjohnson
 * @package   Imageblendedcolorallocate
 * @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/imageblendedcolorallocate
 */

if (!function_exists('imageblendedcolorallocate')) {
    /**
     * Imageblendedcolorallocate is a function that will allocate a new blended color based on two existing allocated
     * colors for your PHP GD images.
     *
     * Examples:
     * ```
     * <?php
     * // Allocate red and yellow using the standard method then blend the two to allocate orange
     * $red    = imagecolorallocate($im, 0xFF, 0x00, 0x00);
     * $yellow = imagecolorallocate($im, 0xFF, 0xFF, 0x00);
     * $orange = imageblendedcolorallocate($im, $red, $yellow);
     *
     * // You can also allocate RGBA colors as well as RGB
     * $opaqueBlack      = imagecolorallocatealpha($im, 0x00, 0x00, 0x00, 0);
     * $translucentBlack = imagecolorallocatealpha($im, 0x00, 0x00, 0x00, 63);
     * $blendedBlack     = imageblendedcolorallocate($im, $opaqueBlack, $translucentBlack);
     *
     * // By default, we allocate with a 50/50 blend where we average the red, blue, green and alpha values for each
     * // color but also support alternative blends
     * $blue              = imagecolorallocate($im, 0x00, 0x00, 0xFF);
     * $cyan              = imagecolorallocate($im, 0x00, 0xFF, 0xFF);
     * $blendedMostlyCyan = imageblendedcolorallocate($im, $blue, $cyan, 0.25); // 25% blue, 75% cyan
     * $blendedEvenly     = imageblendedcolorallocate($im, $blue, $cyan); // 50% blue, 50% cyan
     * $blendedMostlyBlue = imageblendedcolorallocate($im, $blue, $cyan, 0.75); // 75% blue, 25% cyan
     * ?>
     * ```
     *
     * @param \GdImage|resource $image         A GdImage object (PHP 8 and newer) or an image resource (older versions
     * of PHP), returned by one of the image creation functions, such as imagecreatetruecolor().
     * @param int               $color1        A color identifier created with imagecolorallocate().
     * @param int               $color2        A color identifier created with imagecolorallocate().
     * @param double            $opacityColor1 A value between 0 and 1. 1 indicates completely opaque while 0 indicates
     * completely transparent.
     *
     * @return mixed Returns a color identifier or FALSE if the allocation failed.
     */
    function imageblendedcolorallocate(
        $image,
        $color1,
        $color2,
        $opacityColor1 = 0.5
    ) {
        // Calculate $opacityColor2 based on $opacityColor1.
        if ($opacityColor1 >= 0 && $opacityColor1 <= 1) {
            $opacityColor2 = 1 - $opacityColor1;
        } else {
            $opacityColor1 = 0.5;
            $opacityColor2 = 0.5;
        }

        // Calculate $red for the color identifier.
        $redColor1 = ($color1 >> 16) & 0xFF;
        $redColor2 = ($color2 >> 16) & 0xFF;

        $red  = $redColor1 * $opacityColor1;
        $red += $redColor2 * $opacityColor2;
        $red  = round($red);

        // Calculate $green for the color identifier.
        $greenColor1 = ($color1 >> 8) & 0xFF;
        $greenColor2 = ($color2 >> 8) & 0xFF;

        $green  = $greenColor1 * $opacityColor1;
        $green += $greenColor2 * $opacityColor2;
        $green  = round($green);

        // Calculate $blue for the color identifier.
        $blueColor1 = $color1 & 0xFF;
        $blueColor2 = $color2 & 0xFF;

        $blue  = $blueColor1 * $opacityColor1;
        $blue += $blueColor2 * $opacityColor2;
        $blue  = round($blue);

        // Calculate $alpha for the color identifier.
        $alphaColor1 = imagecolorsforindex($image, $color1);
        $alphaColor1 = $alphaColor1['alpha'];
        $alphaColor2 = imagecolorsforindex($image, $color2);
        $alphaColor2 = $alphaColor2['alpha'];

        $alpha  = $alphaColor1 * $opacityColor1;
        $alpha += $alphaColor2 * $opacityColor2;
        $alpha  = round($alpha);

        // If $alpha is greater than zero return an RGBA color identifier otherwise return an RGB color identifier.
        if ($alpha > 0) {
            return imagecolorallocatealpha($image, $red, $green, $blue, $alpha);
        } else {
            return imagecolorallocate($image, $red, $green, $blue);
        }
    }
}