imagick을 사용하는 출력 이미지 파일 크기가 입력보다 커야하는 이유는 무엇입니까?

Question

왜 출력 이미지가 imagick을 사용하는 입력보다 큽니까? 원본 JPG : http://www.persunmall.com/images/jm3.jpg

/** 
* example 
-------------------------------------- 
     'jm3.jpg' => 119 k (453*680) 
     'l.jpg' => 275 k (400*600)  // why the output jpg is much bigger than input jpg? 

*/ 
$jy_image=new jy_image 
$jy_image->output_image('jm3.jpg','l.jpg',400,0); 

수준의 울부 짖는 소리 :

<?php 
class jy_image { 
    private $image = null; 
    private $type = null; 

    // 构造函数 
    public function __construct() { 
    } 


    // 析构函数 
    public function __destruct() { 
     if ($this->image !== null) 
      $this->image->destroy(); 
    } 

    // 载入图像 
    public function open($path) { 
     $this->image = new Imagick($path); 
     if ($this->image) { 
      $this->type = strtolower($this->image->getImageFormat()); // jpeg 
     } 
     return $this->image; 
    } 


    public function crop($x = 0, $y = 0, $width = null, $height = null) { 
     if ($width == null) 
      $width = $this->image->getImageWidth() - $x; 
     if ($height == null) 
      $height = $this->image->getImageHeight() - $y; 
     if ($width <= 0 || $height <= 0) 
      return; 

     if ($this->type == 'gif') { 
      $image = $this->image; 
      $canvas = new Imagick(); 

      $images = $image->coalesceImages(); 
      foreach ($images as $frame) { 
       $img = new Imagick(); 
       $img->readImageBlob($frame); 
       $img->cropImage($width, $height, $x, $y); 

       $canvas->addImage($img); 
       $canvas->setImageDelay($img->getImageDelay()); 
       $canvas->setImagePage($width, $height, 0, 0); 
      } 

      $image->destroy(); 
      $this->image = $canvas; 
     } else { 
      $this->image->cropImage($width, $height, $x, $y); 
     } 
    } 

    /* 
    * 更改图像大小 
    $fit: 适应大小方式 
    'force': 把图片强制变形成 $width X $height 大小 
    'scale': 按比例在安全框 $width X $height 内缩放图片, 输出缩放后图像大小 不完全等于 $width X $height 
    'scale_fill': 按比例在安全框 $width X $height 内缩放图片，安全框内没有像素的地方填充色, 使用此参数时可设置背景填充色 $bg_color = array(255,255,255)(红,绿,蓝, 透明度) 透明度(0不透明-127完全透明)) 
    其它: 智能模能 缩放图像并载取图像的中间部分 $width X $height 像素大小 
    $fit = 'force','scale','scale_fill' 时： 输出完整图像 
    $fit = 图像方位值 时, 输出指定位置部分图像 
    字母与图像的对应关系如下: 

    north_west north north_east 

    west   center  east 

    south_west south south_east 

    */ 
    public function resize_to($width = 100, $height = 100, $fit = 'center', $fill_color = array(255, 255, 255, 0)) { 

     // 保证其中一边，另外一边相应缩放 
     if($width==0 || $height==0){ 
      $image = $this->image; 
      $src_width = $image->getImageWidth(); 
      $src_height = $image->getImageHeight(); 
      if($width>0 && $height==0){ 
       $width=($width>$src_width)?$src_width:$width; 
       $height = $src_height*($width/$src_width); 
      } 
      else if($width==0 && $height>0){ 
       $height=($height>$src_height)?$src_height:$height; 
       $width = $src_width*($height/$src_height); 
      } 
      $fit='force'; 
     } 

     switch ($fit) { 
      case 'force': // 强制缩放，会变形 
       if ($this->type == 'gif') { 
        $image = $this->image; 
        $canvas = new Imagick(); 

        $images = $image->coalesceImages(); 
        foreach ($images as $frame) { 
         $img = new Imagick(); 
         $img->readImageBlob($frame); 
         $img->thumbnailImage($width, $height, false); 

         $canvas->addImage($img); 
         $canvas->setImageDelay($img->getImageDelay()); 
        } 
        $image->destroy(); 
        $this->image = $canvas; 
       } else { 
        $this->image->thumbnailImage($width, $height, false); 
       } 
       break; 
      case 'scale': 
       if ($this->type == 'gif') { 
        $image = $this->image; 
        $images = $image->coalesceImages(); 
        $canvas = new Imagick(); 
        foreach ($images as $frame) { 
         $img = new Imagick(); 
         $img->readImageBlob($frame); 
         $img->thumbnailImage($width, $height, true); 

         $canvas->addImage($img); 
         $canvas->setImageDelay($img->getImageDelay()); 
        } 
        $image->destroy(); 
        $this->image = $canvas; 
       } else { 
        $this->image->thumbnailImage($width, $height, true); 
       } 
       break; 
      case 'scale_fill':  // 填充白色 
       $size  = $this->image->getImagePage(); 
       $src_width = $size['width']; 
       $src_height = $size['height']; 

       $x = 0; 
       $y = 0; 

       $dst_width = $width; 
       $dst_height = $height; 

       if ($src_width * $height > $src_height * $width) { 
        $dst_height = intval($width * $src_height/$src_width); 
        $y   = intval(($height - $dst_height)/2); 
       } else { 
        $dst_width = intval($height * $src_width/$src_height); 
        $x   = intval(($width - $dst_width)/2); 
       } 

       $image = $this->image; 
       $canvas = new Imagick(); 

       $color = 'rgba(' . $fill_color[0] . ',' . $fill_color[1] . ',' . $fill_color[2] . ',' . $fill_color[3] . ')'; 
       if ($this->type == 'gif') { 
        $images = $image->coalesceImages(); 
        foreach ($images as $frame) { 
         $frame->thumbnailImage($width, $height, true); 

         $draw = new ImagickDraw(); 
         $draw->composite($frame->getImageCompose(), $x, $y, $dst_width, $dst_height, $frame); 

         $img = new Imagick(); 
         $img->newImage($width, $height, $color, 'gif'); 
         $img->drawImage($draw); 

         $canvas->addImage($img); 
         $canvas->setImageDelay($img->getImageDelay()); 
         $canvas->setImagePage($width, $height, 0, 0); 
        } 
       } else { 
        $image->thumbnailImage($width, $height, true); 

        $draw = new ImagickDraw(); 
        $draw->composite($image->getImageCompose(), $x, $y, $dst_width, $dst_height, $image); 

        $canvas->newImage($width, $height, $color, $this->get_type()); 
        $canvas->drawImage($draw); 
        $canvas->setImagePage($width, $height, 0, 0); 
       } 
       $image->destroy(); 
       $this->image = $canvas; 
       break; 
      default: 
       $size  = $this->image->getImagePage(); 
       $src_width = $size['width']; 
       $src_height = $size['height']; 

       $crop_x = 0; 
       $crop_y = 0; 

       $crop_w = $src_width; 
       $crop_h = $src_height; 

       if ($src_width * $height > $src_height * $width) { 
        $crop_w = intval($src_height * $width/$height); // 100*50 =>50*100 输出：25*50 
       } else { 
        $crop_h = intval($src_width * $height/$width); //50*100 =>100*50 输出：50*25 
       } 

       switch ($fit) { 
        case 'north_west': 
         $crop_x = 0; 
         $crop_y = 0; 
         break; 
        case 'north': 
         $crop_x = intval(($src_width - $crop_w)/2); 
         $crop_y = 0; 
         break; 
        case 'north_east': 
         $crop_x = $src_width - $crop_w; 
         $crop_y = 0; 
         break; 
        case 'west': 
         $crop_x = 0; 
         $crop_y = intval(($src_height - $crop_h)/2); 
         break; 
        case 'center': 
         $crop_x = intval(($src_width - $crop_w)/2); 
         $crop_y = intval(($src_height - $crop_h)/2); 
         break; 
        case 'east': 
         $crop_x = $src_width - $crop_w; 
         $crop_y = intval(($src_height - $crop_h)/2); 
         break; 
        case 'south_west': 
         $crop_x = 0; 
         $crop_y = $src_height - $crop_h; 
         break; 
        case 'south': 
         $crop_x = intval(($src_width - $crop_w)/2); 
         $crop_y = $src_height - $crop_h; 
         break; 
        case 'south_east': 
         $crop_x = $src_width - $crop_w; 
         $crop_y = $src_height - $crop_h; 
         break; 
        default: 
         $crop_x = intval(($src_width - $crop_w)/2); 
         $crop_y = intval(($src_height - $crop_h)/2); 
       } 

       $image = $this->image; 
       $canvas = new Imagick(); 

       if ($this->type == 'gif') { 
        $images = $image->coalesceImages(); 
        foreach ($images as $frame) { 
         $img = new Imagick(); 
         $img->readImageBlob($frame); 
         $img->cropImage($crop_w, $crop_h, $crop_x, $crop_y); 
         $img->thumbnailImage($width, $height, true); 

         $canvas->addImage($img); 
         $canvas->setImageDelay($img->getImageDelay()); 
         $canvas->setImagePage($width, $height, 0, 0); 
        } 
       } else { 
        $image->cropImage($crop_w, $crop_h, $crop_x, $crop_y); 
        $image->thumbnailImage($width, $height, true); 
        $canvas->addImage($image); 
        $canvas->setImagePage($width, $height, 0, 0); 
       } 
       $image->destroy(); 
       $this->image = $canvas; 
     } 

    } 




    // 添加水印图片 
    public function add_watermark($path, $x = 0, $y = 0) { 

     $watermark = new Imagick($path); 

     // 默认水印位置 by jimmy 2014-4-11 
     if(empty($x) && empty($y)){ 
      $im_w= $this->image->getImageWidth(); 
      $im_h = $this->image->getImageHeight(); 
      $wa_w = $watermark->getImageWidth(); 
      $wa_h = $watermark->getImageHeight(); 
      $x=($im_w-$wa_w)/2; 
      $y=($im_h-$wa_h-50); 
     } 


     $draw  = new ImagickDraw(); 
     $draw->composite($watermark->getImageCompose(), $x, $y, $watermark->getImageWidth(), $watermark->getimageheight(), $watermark); 

     if ($this->type == 'gif') { 
      $image = $this->image; 
      $canvas = new Imagick(); 
      $images = $image->coalesceImages(); 
      foreach ($image as $frame) { 
       $img = new Imagick(); 
       $img->readImageBlob($frame); 
       $img->drawImage($draw); 

       $canvas->addImage($img); 
       $canvas->setImageDelay($img->getImageDelay()); 
      } 
      $image->destroy(); 
      $this->image = $canvas; 
     } else { 
      $this->image->drawImage($draw); 
     } 
    } 


    // 添加水印文字 
    public function add_text($text, $x = 0, $y = 0, $angle = 0, $style = array()) { 
     $draw = new ImagickDraw(); 
     if (isset($style['font'])) 
      $draw->setFont($style['font']); 
     if (isset($style['font_size'])) 
      $draw->setFontSize($style['font_size']); 
     if (isset($style['fill_color'])) 
      $draw->setFillColor($style['fill_color']); 
     if (isset($style['under_color'])) 
      $draw->setTextUnderColor($style['under_color']); 

     if ($this->type == 'gif') { 
      foreach ($this->image as $frame) { 
       $frame->annotateImage($draw, $x, $y, $angle, $text); 
      } 
     } else { 
      $this->image->annotateImage($draw, $x, $y, $angle, $text); 
     } 
    } 


    // 保存到指定路径 
    public function save_to($path) { 
     $this->image->stripImage(); 
     if ($this->type == 'gif') { 
      $this->image->writeImages($path, true); 
     } else { 
      $this->image->writeImage($path); 
     } 
    } 

    // 输出图像 
    public function output($header = true) { 
     if ($header) 
      header('Content-type: ' . $this->type); 
     echo $this->image->getImagesBlob(); 
    } 


    public function get_width() { 
     $size = $this->image->getImagePage(); 
     return $size['width']; 
    } 

    public function get_height() { 
     $size = $this->image->getImagePage(); 
     return $size['height']; 
    } 

    // 设置图像类型， 默认与源类型一致 
    public function set_type($type = 'png') { 
     $this->type = $type; 
     $this->image->setImageFormat($type); 
    } 

    // 获取源图像类型 
    public function get_type() { 
     return $this->type; 
    } 


    // 当前对象是否为图片 
    public function is_image() { 
     if ($this->image) 
      return true; 
     else 
      return false; 
    } 



    public function thumbnail($width = 100, $height = 100, $fit = true) { 
     $this->image->thumbnailImage($width, $height, $fit); 
    } // 生成缩略图 $fit为真时将保持比例并在安全框 $width X $height 内生成缩略图片 

    /* 
    添加一个边框 
    $width: 左右边框宽度 
    $height: 上下边框宽度 
    $color: 颜色: RGB 颜色 'rgb(255,0,0)' 或 16进制颜色 '#FF0000' 或颜色单词 'white'/'red'... 
    */ 
    public function border($width, $height, $color = 'rgb(220, 220, 220)') { 
     $color = new ImagickPixel(); 
     $color->setColor($color); 
     $this->image->borderImage($color, $width, $height); 
    } 

    public function blur($radius, $sigma) { 
     $this->image->blurImage($radius, $sigma); 
    } // 模糊 
    public function gaussian_blur($radius, $sigma) { 
     $this->image->gaussianBlurImage($radius, $sigma); 
    } // 高斯模糊 
    public function motion_blur($radius, $sigma, $angle) { 
     $this->image->motionBlurImage($radius, $sigma, $angle); 
    } // 运动模糊 
    public function radial_blur($radius) { 
     $this->image->radialBlurImage($radius); 
    } // 径向模糊 

    public function add_noise($type = null) { 
     $this->image->addNoiseImage($type == null ? imagick::NOISE_IMPULSE : $type); 
    } // 添加噪点 

    public function level($black_point, $gamma, $white_point) { 
     $this->image->levelImage($black_point, $gamma, $white_point); 
    } // 调整色阶 
    public function modulate($brightness, $saturation, $hue) { 
     $this->image->modulateImage($brightness, $saturation, $hue); 
    } // 调整亮度、饱和度、色调 

    public function charcoal($radius, $sigma) { 
     $this->image->charcoalImage($radius, $sigma); 
    } // 素描 
    public function oil_paint($radius) { 
     $this->image->oilPaintImage($radius); 
    } // 油画效果 

    public function flop() { 
     $this->image->flopImage(); 
    } // 水平翻转 
    public function flip() { 
     $this->image->flipImage(); 
    } // 垂直翻转 

    /** 
    * 压缩图片 by jimmy 2014-4-11 
    * ---------------------------------------- 
    */ 
    function compress($quality=100){ 
     $this->image->setImageFormat('JPEG'); 
     $this->image->setImageCompression(Imagick::COMPRESSION_JPEG); 
     $q = $this->image->getImageCompressionQuality(); 
     $q = $q* $quality/100; 
     if($q==0){ 
      $q = $quality; 
     } 
     $this->image->setImageCompressionQuality($q); 
     $this->image->stripImage(); 
    } 

    /** 
    * 综合各个步骤输出 by jimmy 2014-4-11 
    * ---------------------------------------- 
    */ 
    function output_image($srcFile,$destFile,$w=0,$h=0,$quality=100,$waterFile='',$fit="scale_fill"){ 
     $this->open($srcFile); 
     $this->compress($quality); 
     if(!empty($waterFile)){ 
      $this->add_watermark($waterFile); 
     } 
     if($w+$h>0){ 
      $this->resize_to($w,$h,$fit); 
     } 
     $this->save_to($destFile); 
    } 

} 

Answer 1

첫째, 당신의 의견에서 "도 품질 = (80)는 l.jpg는 jm3.jpg보다 더 크다"그게 잘못된 생각 . 낮은 품질로 파일을 다시 저장하면 다음과 같은 결과가 나타납니다.

119,300 = original image   
266,008 = Resized at 100% 
245,145 = Resized at 100% + despeckle 
97,536 = Resized at 90% quality 
88,342 = Resized at 90% quality with despeckle 

은 또한 얼룩을 도입 할 수 있습니다 크기 조정으로 Imagick::despeckle을 추가했다.

그러나 근본적인 질문은 "왜 JPEG 이미지를 다시 저장하면 동일한 품질로 파일 크기가 늘어 납니까?"라고 묻는 것입니다.

단순한 대답은 손실 형식이므로 이미지를 JPEG로 저장 한 후 새 이미지에 더 많은 정보가있을 수 있다는 것입니다. 동일한 품질로 이미지를 저장하려면 추가 정보를 인코딩해야하므로 추가 공간이 필요합니다.

간단한 사인파를 고려하십시오. 그것은 아주 적은 정보를 담고 있습니다. 당신이 그것을 필요로 더 많은 정보를 가지고 새로운 형태를 고려하는 방법과 상관없이

: 그럼 우리가 같은 즉 사인파 떨어져 끝을 트리밍 손실 형식, '이미지로 저장'상상 새로운 도형을 유지하도록 인코딩되므로 100 % 품질로 다시 저장하면 원래의 손실 저장된 이미지보다 더 많은 공간이 필요합니다.

낮은 품질로 다시 저장하면 이미지가 작아 지지만 각 절약은 대략적인 근사치이므로 이미지에서 정보가 빠르게 손실됩니다.

TL : DR은 모든 중간 형식에 PNG를 사용하고 고객에게 최종 출력물로만 JPG를 사용합니다.