rsnongfa/app/common/service/ImageCompressService.php

<?php

namespace app\common\service;

use Exception;

class ImageCompressService
{
    /**
     * 压缩图片
     * @param string $sourcePath 源文件路径
     * @param int $quality 压缩质量 (1-100)
     * @param int $maxWidth 最大宽度
     * @param int $maxHeight 最大高度
     * @return string|false 压缩后的文件路径
     */
    public static function compress($sourcePath, $quality = 80, $maxWidth = 1920, $maxHeight = 1080)
    {
        try {
            // 获取图片信息
            $imageInfo = getimagesize($sourcePath);
            if (!$imageInfo) {
                throw new Exception('无法获取图片信息');
            }

            $width = $imageInfo[0];
            $height = $imageInfo[1];
            $type = $imageInfo[2];

            // 如果图片尺寸已经很小，且质量要求不高，直接返回原文件
            if ($width <= $maxWidth && $height <= $maxHeight && $quality >= 90) {
                return $sourcePath;
            }

            // 计算新尺寸
            $newSize = self::calculateNewSize($width, $height, $maxWidth, $maxHeight);
            $newWidth = $newSize['width'];
            $newHeight = $newSize['height'];

            // 创建源图片资源
            $sourceImage = self::createImageFromType($sourcePath, $type);
            if (!$sourceImage) {
                throw new Exception('不支持的图片格式');
            }

            // 创建新图片资源
            $newImage = imagecreatetruecolor($newWidth, $newHeight);
            
            // 处理透明背景（PNG/GIF）
            if ($type == IMAGETYPE_PNG || $type == IMAGETYPE_GIF) {
                imagealphablending($newImage, false);
                imagesavealpha($newImage, true);
                $transparent = imagecolorallocatealpha($newImage, 255, 255, 255, 127);
                imagefill($newImage, 0, 0, $transparent);
            }

            // 重新采样
            imagecopyresampled($newImage, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);

            // 生成压缩后的文件路径
            $compressedPath = self::generateCompressedPath($sourcePath);

            // 保存压缩后的图片
            $result = self::saveImageByType($newImage, $compressedPath, $type, $quality);

            // 释放内存
            imagedestroy($sourceImage);
            imagedestroy($newImage);

            return $result ? $compressedPath : false;

        } catch (Exception $e) {
            return false;
        }
    }

    /**
     * 计算新尺寸（保持宽高比）
     */
    private static function calculateNewSize($width, $height, $maxWidth, $maxHeight)
    {
        $ratio = min($maxWidth / $width, $maxHeight / $height, 1);
        return [
            'width' => intval($width * $ratio),
            'height' => intval($height * $ratio)
        ];
    }

    /**
     * 根据图片类型创建图片资源
     */
    private static function createImageFromType($path, $type)
    {
        switch ($type) {
            case IMAGETYPE_JPEG:
                return imagecreatefromjpeg($path);
            case IMAGETYPE_PNG:
                return imagecreatefrompng($path);
            case IMAGETYPE_GIF:
                return imagecreatefromgif($path);
            case IMAGETYPE_WEBP:
                return imagecreatefromwebp($path);
            default:
                return false;
        }
    }

    /**
     * 根据图片类型保存图片
     */
    private static function saveImageByType($image, $path, $type, $quality)
    {
        switch ($type) {
            case IMAGETYPE_JPEG:
                return imagejpeg($image, $path, $quality);
            case IMAGETYPE_PNG:
                // PNG压缩级别 0-9，质量参数需要转换
                $pngQuality = intval((100 - $quality) / 10);
                return imagepng($image, $path, $pngQuality);
            case IMAGETYPE_GIF:
                return imagegif($image, $path);
            case IMAGETYPE_WEBP:
                return imagewebp($image, $path, $quality);
            default:
                return false;
        }
    }

    /**
     * 生成压缩后的文件路径
     */
    private static function generateCompressedPath($originalPath)
    {
        $pathInfo = pathinfo($originalPath);
        return $pathInfo['dirname'] . '/' . $pathInfo['filename'] . '_compressed.' . $pathInfo['extension'];
    }
}