php 如何将image图片转化为字符串(GD库操作及imagick两种实现方式)

前两天研究php中的 imagick 扩展的时候，突发奇想实现的一个小功能感觉挺有意思，在这里记录一下：

将一张image图片转化为字符串的形式，先上一张效果图。（运行笔记中的代码需要先安装 php_imagick 扩展 教程可以看这里：PHP扩展之 Imagick安装）

                                                                                                                                              
                                                                                                                                              
                                                                                                                                              
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原图：

<?php
/**
* 图片转换为字符图
* @param string $imagePath 图片地址
* @param int $width x轴方向缩放比例
* @param int $height y轴方向缩放比例
* @return string 生成的字符串图
*/
function img2String($imagePath,$width=1,$height=1)
{
    //检查是否安装 php_imagick 扩展
    if(!extension_loaded("imagick")){
        exit("请先安装 imagick 模块");
    }
    $imagick = new Imagick(realpath($imagePath));
    //将生成的imagick对象转化为一个像素迭代器，可以从该迭代器中获取没个像素的 rgb 的值。不知道什么是rgb的请问度娘
    $imageIterator = new ImagickPixelIterator($imagick);
     $str='O80GCLft*+;:,. ';
    foreach ($imageIterator as $rows => $pixels) {
            if($rows%$width == 1 || $width == 1){
                echo "
";
                foreach ($pixels as $column => $pixel) {
                    if($column%$height == 1 || $height == 1){
                        //灰度计算公式  某个像素点的灰度值 = 红色值*0.3 + 绿色值 * 0.59 + 蓝色值 * 0.11
                        $gray = $pixel->getColor()['r']*0.3 + $pixel->getColor()['g']*0.59 + $pixel->getColor()['b']*0.11;
                        //由于 rgb 三原色的数值范围在 [0,255] 所以求出的灰度值的范围也是 [0,255],所以我们计算像素的 "饱和度" = 灰度值/255;
                        $r = $gray/255;
                        //根据像素的 "饱和度" 选择合适的字符
                        $offset=(int)ceil($r*(strlen($str)-1));    
                        if($offset==(strlen($str)-1)){
                            echo " ";
                        }else{
                            echo $str[$offset];  
                        }
                    }         
                }
                $imageIterator->syncIterator();
            }    
    }
}

img2String('huawei.jpg',2,1);

 GD实现效果（不需要安装imagick）

/**
* 图片转为字符串
* @param string $img_src 图片地址
* @param int $width_index 横向缩放比例
* @param int $height_index 纵向缩放比例
* @return string 生成的字符串
**/
function img2str($img_src,$width_index,$height_index){
    $resource = imagecreatefromjpeg($img_src);
    $width = imagesx($resource);
    $height = imagesy($resource);
    imagefilter($resource, IMG_FILTER_GRAYSCALE);

    for ($i=0; $i < $height; $i++) {
        if($i%$height_index==0){
            for ($j=0; $j < $width; $j++) {
                if($j%$width_index==0){
                    $color_index = imagecolorat($resource, $j, $i);
                    $rgb = imagecolorsforindex($resource,$color_index);
                    $gray = $rgb['red'];
                    $str='O80GCLft*+;:,. ';
                    $r = $gray/255;
                    $offset=(int)ceil($r*(strlen($str)-1));
                    echo $str[$offset];
                }
            }
            echo "
";
        }
    }
}

img2str("./huawei.jpg",1,2);