php比例缩放图片及剪切图片

摘要：图片缩放函数可设置高度固定，宽度固定或者最大宽高，支持三种类型源图片目标宽度目标高度锁定宽高可选参数或者空值宽度固定高度固定最大宽或最大高用法最大宽高宽度固定高度固定剪切图片为固定大小源图过高源图过宽源图适中裁剪缩放

/**
 * 图片缩放函数（可设置高度固定，宽度固定或者最大宽高，支持gif/jpg/png三种类型）
 * Author : Specs
 *
 * @param string $source_path 源图片
 * @param int $target_width 目标宽度
 * @param int $target_height 目标高度
 * @param string $fixed_orig 锁定宽高（可选参数 width、height或者空值）
 * @return string
 */
function myImageResize($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"){
        //宽度固定
        $target_height = $target_width / $ratio_orig;
    }elseif ($fixed_orig == "height"){
        //高度固定
        $target_width = $target_height * $ratio_orig;
    }else{
        //最大宽或最大高
        if ($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($filename, 200, 200); //最大宽高
myImageResize($filename, 200, 200, "width"); //宽度固定
myImageResize($filename, 200, 200, "height"); //高度固定

剪切图片为固定大小：

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;
    
    // 源图过高
    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){ // 源图过宽
        $cropped_width = $source_height / $target_ratio;
        $cropped_height = $source_height;
        $source_x = ($source_width - $cropped_width) / 2;
        $source_y = 0;
    }else{ // 源图适中
        $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, $cropped_height);
    // 缩放
    imagecopyresampled($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);
}