图片转字符画

一个有趣的程序。

主要技术包含图片拖拽、粘贴、双击上传，然后通过canvas获得图片每一像素的rgb颜色值，然后按颜色值总体大小使用相应的字符代替形成字符画。

原图：

转换后：

代码：

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>image2char</title>
    <style>
    .imageUploader {}
    .imageUploader .eventContainerDiv {width:100%;height:100px;min-width:300px;min-height:100px;border:3px dashed silver;padding:4px;cursor:default;}
    .imageUploader .eventContainerDiv img {display:none;overflow-x:auto;}
    .imageUploader .imageContainerDiv .imageBox {width:200px;height:150px;float:left;margin:4px;border:1px solid #eee;}
    .imageUploader .imageContainerDiv .imageBox img {max-width:100%;max-height:100%;object-fit: cover;}
    .imageUploader .imageContainerDiv .imageBox button {height:28px;margin-top:-28px;position: absolute;}
    .pixel-container {margin:0;padding:0;}
    .pixel-row {display:flex;}
    .pixel {width:12px;height:12px;margin:0;padding:0;font-size:12px;font-family:宋体;}
    </style>
</head>
<body>
 
<input type="hidden" id="article_link_image" name="article_link_image" value=""/>
<div id="imageUploader" class="imageUploader" upload="" maxWidth="400" maxHeight="600" limitCount="1"></div>
<div id="imageShow"></div>
</body>
 
<script>
 
 
    // 拖拽上传，兼容IE、FireFox、Chrome
    function dragEventProcess(eventContainerDiv,upload){
        document.addEventListener("dragenter", function(e){
            eventContainerDiv.style.borderColor = 'gray';
        }, false);
        document.addEventListener("dragleave", function(e){
            eventContainerDiv.style.borderColor = 'silver';
        }, false);
        eventContainerDiv.addEventListener("dragenter", function(e){
            eventContainerDiv.style.borderColor = 'gray';
            eventContainerDiv.style.backgroundColor = 'white';
        }, false);
        eventContainerDiv.addEventListener("dragleave", function(e){
            eventContainerDiv.style.backgroundColor = 'transparent';
        }, false);
        eventContainerDiv.addEventListener("dragenter", function(e){
            e.stopPropagation();
            e.preventDefault();
        }, false);
        eventContainerDiv.addEventListener("dragover", function(e){
            e.stopPropagation();
            e.preventDefault();
        }, false);
        eventContainerDiv.addEventListener("drop", function(e){
            e.stopPropagation();
            e.preventDefault();
            var imageFile = e.dataTransfer.files[0];
            loadImage(imageFile);
            //submit.disabled = false;
        }, false);
    }
 
 
    // 粘贴上传，兼容IE、FireFox、Chrome
    function pasteEventProcess(eventContainerDiv,upload){
        eventContainerDiv.addEventListener("paste", function(event){
            // console.log(event);
            // console.log(clipboardData);
            // chrome、edge、firefox，不管粘贴截图还是网络图片都能从clipboardData中得到图片二进制数据。
            if ( event.clipboardData || event.originalEvent ) {
                var clipboardData = (event.clipboardData || event.originalEvent.clipboardData);
                if ( clipboardData.items ) {
                    var  items = clipboardData.items;
                    for (var i = 0; i < items.length; i++) {
                        // console.log(items[i].type);
                        if (items[i].type.indexOf("image") !== -1) {
                            var imageFile = items[i].getAsFile();
                            loadImage(imageFile);
                        }
                    }
 
                }
            }else {
                alert('the browser is not support.');
            }
        }, false);
    }
 
 
    // 双击上传
    function dblclickEventProcess(eventContainerDiv,upload){
        eventContainerDiv.addEventListener("dblclick", function(event){
            // 触发上一个元素(input file)的点击事件
            eventContainerDiv.previousElementSibling.click();
        });
    }
 
 
    function clearEventContainerDivImages(eventContainerDiv){
        eventContainerDiv.setAttribute("count", "0");
        var images = eventContainerDiv.querySelectorAll("img");
        for(var i=0;i<images.length;i++){
            eventContainerDiv.removeChild(images[i]);
        }
    }
 
    // 初始化函数
    function initialize(){
        var imageUploaders = document.querySelectorAll(".imageUploader");
        if(imageUploaders && imageUploaders.length > 0){
 
            for(var i=0;i<imageUploaders.length;i++){
                var uploader = imageUploaders[i];
                // 如果已经初始化过则跳过。
                if(uploader.getAttribute("initialized") == "true") continue;
                 
                var upload = uploader.getAttribute("upload");
                var eventContainerDiv = document.createElement("div");
                // 往div里创建一个input file标签，用于双击选择文件上传
                var input = document.createElement("input");
                input.type = "file";
                input.style.display = "none";
                input.onchange = function(event){
                    var evt = window.event || event;
                    var evtsrc = evt.srcElement || evt.target;
                    //console.log(evtsrc.parentNode.id);
                    var imageFile = evtsrc.files[0];
                    loadImage(imageFile);
                };
                uploader.appendChild(input);
 
                // 往div里创建两个div，分别作为拖放粘贴双击容器和图片上传后的呈现容器
                eventContainerDiv.className = "eventContainerDiv";
                eventContainerDiv.contentEditable = true;
                eventContainerDiv.innerHTML = "请将图片粘贴或拖拽到此区域,或双击此区域选择图片进行上传.";
 
 
                // 绑定拖拽事件及处理
                dragEventProcess(eventContainerDiv,upload);
                // 绑定粘贴事件及处理
                pasteEventProcess(eventContainerDiv,upload);
                // 绑定双击事件及处理
                dblclickEventProcess(eventContainerDiv,upload);
                // 添加到容器里
                uploader.appendChild(eventContainerDiv);
                var imageContainerDiv = document.createElement("div");
                imageContainerDiv.className = "imageContainerDiv";
 
                // 添加到容器里
                uploader.appendChild(imageContainerDiv);
 
 
 
                uploader.setAttribute("initialized", "true");
 
            }
        }
    }
 
 
    window.addEventListener("load",function(){
        // 在window下设置一个初始化函数,用于可动态地初始化组件(用js动态创建的组件,需要动态初始化)。
        window.powerfulImageUploadInitialize = initialize;
        powerfulImageUploadInitialize();
    },false);
 
 
  function group(array, subGroupLength) {
      let index = 0;
      let newArray = [];
      while(index < array.length) {
          newArray.push(array.slice(index, index += subGroupLength));
      }
      return newArray;
  }
   
    function loadImage(imageFile) {
        var canvas = document.createElement('canvas'); 
        var context = canvas.getContext('2d');
        var reader = new FileReader(); 
        reader.readAsDataURL(imageFile); 
        reader.onload = function(e){ // reader onload start 
          var image = new Image(); 
          image.src = e.target.result; 
          image.onload = function(){ // image onload start 
            var img_width = this.width; 
            var img_height = this.height; 
            // 设置画布尺寸 
            canvas.width = img_width; 
            canvas.height = img_height; 
            // 将图片按像素写入画布 
            context.drawImage(this, 0, 0, img_width, img_height); 
            // 读取图片像素信息 
            var imageData = context.getImageData(0, 0, img_width, img_height); 
            var colorRows = group(imageData.data, img_width * 4); // 每4个元素表示一个像素的rgba。
            imageRGB2Char(colorRows);
          }
          
        }
    }
     
    function imageRGB2Char(colorRows) {
        var html = '';
        console.log('colorRows.length:', colorRows.length);
        for (var x=0; x<colorRows.length; x++) {
            html += '<div class="pixel-row">';
            var cells = colorRows[x];
            console.log('cells.length', cells.length);
            for (var y=0; y<cells.length; y++) {
                if(y%4 === 0){ // 每四个元素为一个像素数据 r,g,b,alpha 
                    // 这里只取rgb，不取a
                    var rgb = cells[y] + ',' + cells[y+1] + ',' + cells[y+2];
                    // html += '<div class="pixel" style="background-color: rgb('+ rgb2char(rgb) +');"></div>';
                    html += '<div class="pixel" style="color: rgb('+ rgb +');">' + rgb2char(rgb) + '</div>';
                } 
            }
            html += '</div>';
        }
        document.getElementById('imageShow').innerHTML = html;
    }
     
    function rgb2char(rgb) {
        rgb = eval(rgb.replaceAll(',', '+'));
        var charr = '';
        if (rgb >= 722) {
            charr = "  ";
        } else if (rgb >= 684 && rgb < 722) {
            charr = ";;";
        } else if (rgb >= 646 && rgb < 684) {
            charr = "\'\'";
        } else if (rgb >= 608 && rgb < 646) {
            charr = "..";
        } else if (rgb >= 570 && rgb < 608) {
            charr = ",,";
        } else if (rgb >= 532 && rgb < 570) {
            charr = "::";
        } else if (rgb >= 494 && rgb < 532) {
            charr = "tt";
        } else if (rgb >= 456 && rgb < 494) {
            charr = "rr";
        } else if (rgb >= 418 && rgb < 456) {
            charr = "ff";
        } else if (rgb >= 380 && rgb < 418) {
            charr = "kk";
        } else if (rgb >= 342 && rgb < 380) {
            charr = "ZZ";
        } else if (rgb >= 304 && rgb < 342) {
            charr = "FF";
        } else if (rgb >= 266 && rgb < 304) {
            charr = "XX";
        } else if (rgb >= 228 && rgb < 266) {
            charr = "##";
        } else if (rgb >= 190 && rgb < 228) {
            charr = "BB";
        } else if (rgb >= 152 && rgb < 190) {
            charr = "HH";
        } else if (rgb >= 114 && rgb < 152) {
            charr = "WW";
        } else if (rgb >= 76 && rgb < 114) {
            charr = "NN";
        } else if (rgb >= 38 && rgb < 76) {
            charr = "@@";
        } else if (rgb >= 0 && rgb < 38) {
            charr = "MM";
        }
        return charr;
    }
     
</script>
</html>