xyzshop/helper/tools/image_scaler.php

<?php
/**
 * Created by PhpStorm.
 * User: lionared
 * Date: 2018/6/6
 * Time: 上午11:12
 */

namespace tools;

class image_scaler
{
    private $mOutImage;
    private $mInImage;

    private $mCx;
    private $mCy;
    public function __construct($width,$height)
    {
        $this->mOutImage = imagecreatetruecolor($width,$height);
        $this->mCx = $width;
        $this->mCy = $height;
    }

    public function __destruct()
    {
        @imagedestroy($this->mOutImage);
        @imagedestroy($this->mInImage);
    }

    public function scale($filename,$scale)
    {
        $ret = $this->read($filename);
        if($ret == false) return false;

        $cx = imagesx($this->mInImage);
        $cy = imagesy($this->mInImage);

        $size = $this->calc($cx,$cy,$scale);
        $dx = $size['cx'];
        $dy = $size['cy'];
        $x = intval(($cx - $dx) / 2 + 0.5);
        $y = intval(($cy - $dy) / 2 + 0.5);

        imagecopyresized($this->mOutImage, $this->mInImage,0,0, $x, $y, $this->mCx,$this->mCy,$dx,$dy);
        return true;
    }

    public function getImage() {
        return $this->mOutImage;
    }

    private function calc($cx,$cy,$scale)
    {
        $dx = intval($cy * $scale + 0.5);
        $cx = intval($cx);
        if($cx > $dx) {
            return ['cx' => $dx,'cy' => $cy];
        }
        elseif($cx == $dx) {
            return ['cx' => $cx,'cy' => $cy];
        }
        else {
            return ['cx' => $cx,'cy' => intval($cx / $scale + 0.5)];
        }
    }

    private function read($file)
    {
        $imagetype = exif_imagetype($file);
        if (! $imagetype) {
            return false;
        }
        switch ($imagetype)
        {
            case IMAGETYPE_GIF:
                $this->mInImage = @imagecreatefromgif($file);
                break;
            case IMAGETYPE_JPEG:
            case IMAGETYPE_JPEG2000:
                $this->mInImage = @imagecreatefromjpeg($file);
                break;
            case IMAGETYPE_PNG:
                $this->mInImage = @imagecreatefrompng($file);
                break;
            case IMAGETYPE_BMP:
                $this->mInImage = $this->imagecreatefrombmp($file);
                break;
            default:
                return false;
        }
        return true;
    }

    private function imagecreatefrombmp($filename)
    {
        $file = fopen( $filename, "rb" );
        $read = fread( $file, 10 );
        while( !feof( $file ) && $read != "" )
        {
            $read .= fread( $file, 1024 );
        }
        $temp = unpack( "H*", $read );
        $hex = $temp[1];
        $header = substr( $hex, 0, 104 );
        $body = str_split( substr( $hex, 108 ), 6 );
        if( substr( $header, 0, 4 ) == "424d" )
        {
            $header = substr( $header, 4 );
            // Remove some stuff?
            $header = substr( $header, 32 );
            // Get the width
            $width = hexdec( substr( $header, 0, 2 ) );
            // Remove some stuff?
            $header = substr( $header, 8 );
            // Get the height
            $height = hexdec( substr( $header, 0, 2 ) );
            unset( $header );
        }
        $x = 0;
        $y = 1;

        $image = imagecreatetruecolor( $width, $height );
        foreach( $body as $rgb )
        {
            $r = hexdec( substr( $rgb, 4, 2 ) );
            $g = hexdec( substr( $rgb, 2, 2 ) );
            $b = hexdec( substr( $rgb, 0, 2 ) );
            $color = imagecolorallocate( $image, $r, $g, $b );
            imagesetpixel( $image, $x, $height-$y, $color );
            $x++;
            if( $x >= $width )
            {
                $x = 0;
                $y++;
            }
        }
        return $image;
    }
}