Question

我刚刚编写了PHP代码来压缩图像大小。我的代码压缩图像但不是所有时间。在10％的情况下，它会增加图像大小。请告诉我为什么会这样？这是我的代码:(这里有两个函数，一个用于png图像，另一个用于jpg图像）

 function compressImageSmall($source_url, $destination_url, $quality) {
    //$quality :: 0 - 100
    $info = getimagesize($source_url);

    if ($info['mime'] == 'image/jpeg')
    {
        $image = imagecreatefromjpeg($source_url);
        //save file
        imagejpeg($image, $destination_url, $quality);//ranges from 0 (worst quality, smaller file) to 100 (best quality, biggest file). The default is the default IJG quality value (about 75).
        //Free up memory
        imagedestroy($image);
    }
    elseif ($info['mime'] == 'image/png')
    {
        $image = imagecreatefrompng($source_url);

        //imagepng($image);

        imageAlphaBlending($image, true);
        imageSaveAlpha($image, true);

        /* chang to png qulity*/ 
        $png_quality = 9 - (($quality * 9 ) / 100 );
        imagePng($image, $destination_url, $png_quality);//Compression level: from 0 (no compression) to 9.
        //Free up memory
        imagedestroy($image);

    }

    //return destination file
    return $destination_url;
}


function compressImage($source_url, $destination_url, $quality) {
    $info = getimagesize($source_url);

    if ($info['mime'] == 'image/jpeg') $image = imagecreatefromjpeg($source_url);
    elseif ($info['mime'] == 'image/gif') $image = imagecreatefromgif($source_url);
    elseif ($info['mime'] == 'image/png') $image = imagecreatefrompng($source_url);

    //save it
    //echo '<pre>';print_r(imagejpeg($image));//
    imagejpeg($image, $destination_url, $quality);

    //return destination file url
    return $destination_url;
}

Answer 1

内置像imagejpeg，imagepngImage等功能的Php可以方便地压缩图像。以下是图像压缩的完整代码示例：How to compress image file while uploading - PHP example ...

图像压缩会增加PHP中的文件大小

1 个答案: