摘要：圖片縮放函數可設置高度固定，寬度固定或者最大寬高，支持三種類型源圖片目標寬度目標高度鎖定寬高可選參數或者空值寬度固定高度固定最大寬或最大高用法最大寬高寬度固定高度固定剪切圖片為固定大小源圖過高源圖過寬源圖適中裁剪縮放

/**
 * 圖片縮放函數（可設置高度固定，寬度固定或者最大寬高，支持gif/jpg/png三種類型）
 * Author : Specs
 *
 * @param string $source_path 源圖片
 * @param int $target_width 目標寬度
 * @param int $target_height 目標高度
 * @param string $fixed_orig 鎖定寬高（可選參數 width、height或者空值）
 * @return string
 */
function myImageResize($source_path, $target_width = 200, $target_height = 200, $fixed_orig = ""){
    $source_info = getimagesize($source_path);
    $source_width = $source_info[0];
    $source_height = $source_info[1];
    $source_mime = $source_info["mime"];
    $ratio_orig = $source_width / $source_height;
    if ($fixed_orig == "width"){
        //寬度固定
        $target_height = $target_width / $ratio_orig;
    }elseif ($fixed_orig == "height"){
        //高度固定
        $target_width = $target_height * $ratio_orig;
    }else{
        //最大寬或最大高
        if ($target_width / $target_height > $ratio_orig){
            $target_width = $target_height * $ratio_orig;
        }else{
            $target_height = $target_width / $ratio_orig;
        }
    }
    switch ($source_mime){
        case "image/gif":
            $source_image = imagecreatefromgif($source_path);
            break;
        
        case "image/jpeg":
            $source_image = imagecreatefromjpeg($source_path);
            break;
        
        case "image/png":
            $source_image = imagecreatefrompng($source_path);
            break;
        
        default:
            return false;
            break;
    }
    $target_image = imagecreatetruecolor($target_width, $target_height);
    imagecopyresampled($target_image, $source_image, 0, 0, 0, 0, $target_width, $target_height, $source_width, $source_height);
    //header("Content-type: image/jpeg");
    $imgArr = explode(".", $source_path);
    $target_path = $imgArr[0] . "_new." . $imgArr[1];
    imagejpeg($target_image, $target_path, 100);
}

用法：

myImageResize($filename, 200, 200); //最大寬高
myImageResize($filename, 200, 200, "width"); //寬度固定
myImageResize($filename, 200, 200, "height"); //高度固定

剪切圖片為固定大小：

function imagecropper($source_path, $target_width, $target_height){
    $source_info = getimagesize($source_path);
    $source_width = $source_info[0];
    $source_height = $source_info[1];
    $source_mime = $source_info["mime"];
    $source_ratio = $source_height / $source_width;
    $target_ratio = $target_height / $target_width;
    
    // 源圖過高
    if ($source_ratio > $target_ratio){
        $cropped_width = $source_width;
        $cropped_height = $source_width * $target_ratio;
        $source_x = 0;
        $source_y = ($source_height - $cropped_height) / 2;
    }elseif ($source_ratio < $target_ratio){ // 源圖過寬
        $cropped_width = $source_height / $target_ratio;
        $cropped_height = $source_height;
        $source_x = ($source_width - $cropped_width) / 2;
        $source_y = 0;
    }else{ // 源圖適中
        $cropped_width = $source_width;
        $cropped_height = $source_height;
        $source_x = 0;
        $source_y = 0;
    }
    
    switch ($source_mime){
        case "image/gif":
            $source_image = imagecreatefromgif($source_path);
            break;
        
        case "image/jpeg":
            $source_image = imagecreatefromjpeg($source_path);
            break;
        
        case "image/png":
            $source_image = imagecreatefrompng($source_path);
            break;
        
        default:
            return false;
            break;
    }
    
    $target_image = imagecreatetruecolor($target_width, $target_height);
    $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);
    
    // 裁剪
    imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
    // 縮放
    imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);
    $dotpos = strrpos($source_path, ".");
    $imgName = substr($source_path, 0, $dotpos);
    $suffix = substr($source_path, $dotpos);
    $imgNew = $imgName . "_small" . $suffix;
    imagejpeg($target_image, $imgNew, 100);
    imagedestroy($source_image);
    imagedestroy($target_image);
    imagedestroy($cropped_image);
}