轻松掌握PHP：图片上传与精准裁切技巧全解析

1. 图片上传基础

1.1 配置上传目录

首先，需要确保服务器上的一个目录允许文件写入，并设置正确的权限。

$uploadDir = 'uploads/';
if (!file_exists($uploadDir)) {
    mkdir($uploadDir, 0755, true);
}

1.2 检查文件上传

在处理文件上传时，PHP提供了一个非常方便的函数$_FILES，可以用来检查上传的文件。

if ($_FILES['file']['error'] == 0) {
    // 文件上传成功
} else {
    // 文件上传失败，错误代码见：http://www.php.net/manual/en/features.file-upload.errors.php
}

1.3 文件类型验证

$validTypes = array(IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF);
if (!in_array(getimagesize($_FILES['file']['tmp_name'])[2], $validTypes)) {
    // 不是有效的图片类型
}

1.4 保存文件

将上传的文件移动到服务器上的指定目录。

move_uploaded_file($_FILES['file']['tmp_name'], $uploadDir . basename($_FILES['file']['name']));

2. 图片裁切与缩放

2.1 使用GD库裁切图片

function cropImage($sourcePath, $destinationPath, $x, $y, $width, $height) {
    list($sourceWidth, $sourceHeight, $type) = getimagesize($sourcePath);
    
    switch ($type) {
        case IMAGETYPE_JPEG:
            $sourceImage = imagecreatefromjpeg($sourcePath);
            break;
        case IMAGETYPE_PNG:
            $sourceImage = imagecreatefrompng($sourcePath);
            break;
        case IMAGETYPE_GIF:
            $sourceImage = imagecreatefromgif($sourcePath);
            break;
    }
    
    $croppedImage = imagecrop($sourceImage, ['x' => $x, 'y' => $y, 'width' => $width, 'height' => $height]);
    imagejpeg($croppedImage, $destinationPath);
    imagedestroy($sourceImage);
    imagedestroy($croppedImage);
}

2.2 图片缩放

function resizeImage($sourcePath, $destinationPath, $width, $height) {
    list($sourceWidth, $sourceHeight, $type) = getimagesize($sourcePath);
    
    switch ($type) {
        case IMAGETYPE_JPEG:
            $sourceImage = imagecreatefromjpeg($sourcePath);
            break;
        case IMAGETYPE_PNG:
            $sourceImage = imagecreatefrompng($sourcePath);
            break;
        case IMAGETYPE_GIF:
            $sourceImage = imagecreatefromgif($sourcePath);
            break;
    }
    
    $targetImage = imagecreatetruecolor($width, $height);
    imagecopyresampled($targetImage, $sourceImage, 0, 0, 0, 0, $width, $height, $sourceWidth, $sourceHeight);
    imagejpeg($targetImage, $destinationPath);
    imagedestroy($sourceImage);
    imagedestroy($targetImage);
}

3. 总结