更高质量的缩略图 [英] Better quality thumbnails

问题描述

我有一个成功创建缩略图的脚本，但它们的渲染质量很低.是否可以在脚本中更改某些内容以提高缩略图的质量?

I have a script that successfully creates thumbnails but they're rendered low quality. Is there something that I can change in the script to make the thumbnails better quality?

function createThumbnail($filename) {

    $final_width_of_image = 200;
    $path_to_image_directory = 'images/fullsized/';
    $path_to_thumbs_directory = 'images/thumbs/';

    if(preg_match('/[.](jpg)$/', $filename)) {
        $im = imagecreatefromjpeg($path_to_image_directory . $filename);
    } else if (preg_match('/[.](gif)$/', $filename)) {
        $im = imagecreatefromgif($path_to_image_directory . $filename);
    } else if (preg_match('/[.](png)$/', $filename)) {
        $im = imagecreatefrompng($path_to_image_directory . $filename);
    }

    $ox = imagesx($im);
    $oy = imagesy($im);

    $nx = $final_width_of_image;
    $ny = floor($oy * ($final_width_of_image / $ox));

    $nm = imagecreatetruecolor($nx, $ny);

    imagecopyresized($nm, $im, 0,0,0,0,$nx,$ny,$ox,$oy);

    if(!file_exists($path_to_thumbs_directory)) {
      if(!mkdir($path_to_thumbs_directory)) {
           die("There was a problem. Please try again!");
      }
       }

    imagejpeg($nm, $path_to_thumbs_directory . $filename);
    $tn = '<img src="' . $path_to_thumbs_directory . $filename . '" alt="image" />';
    $tn .= '<br />Congratulations. Your file has been successfully uploaded, and a thumbnail has been created.';
    echo $tn;   
}

推荐答案

我只能用这段代码建议:

The only things I can suggest with this code are:

• 增加 $final_width_of_image 以制作更大的缩略图.
• 向 imagejpeg 添加第三个 quality 参数；根据PHP手册，范围从0到100，100是最好的质量.
• 不要将 JPEG 用于缩略图.
• 使用 imagecopyresampled 获得更好的像素插值算法.

• Increase the $final_width_of_image to make a larger thumbnail.
• Add the third quality argument to imagejpeg; according to the PHP manual, it ranges from 0 to 100 with 100 being the best quality.
• Don't use JPEG for your thumbnails.
• Use imagecopyresampled to get a better pixel interpolation algorithm.

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