将base64转换为javascript/jquery中的图像

Question

我用javascript/jquery编写了一些图像捕获代码.下面是代码:

function capture_image(){ 
    alert("capture_image");
    var p = webcam.capture();
    webcam.save();           
    alert("capture complete "+p); //getting true here


     var img = canvas.toDataURL("image");
    var item_image = img.replace(/^data:image\/(png|jpg);base64,/, "") ; 
    alert("item_image"+item_image);
}

item_image打印base64格式,如何将base64转换为图像以及如何在javascript客户端中使用该路径.

我搜索谷歌这么多的网站,但它不工作,该代码不适合我的要求.

Answer 1

你可以创建一个Image对象,并把以base64为src,包括data:image...一部分这样的:

var image = new Image();
image.src = 'data:image/png;base64,iVBORw0K...';
document.body.appendChild(image);

这就是他们所谓的"数据URI",这里是内心和平的兼容性表.

Answer 2

这不是OP的情况,而是对一些评论者的回答.它是基于Cordova和Angular 1的解决方案,应该适用于其他框架,如jQuery.它为您提供了Base64数据的Blob,您可以将其存储在某处并从客户端javascript/html引用它.

它还回答了关于如何从Base 64数据中获取图像(文件)的原始问题:

重要的部分是Base 64 - 二进制转换:

function base64toBlob(base64Data, contentType) {
    contentType = contentType || '';
    var sliceSize = 1024;
    var byteCharacters = atob(base64Data);
    var bytesLength = byteCharacters.length;
    var slicesCount = Math.ceil(bytesLength / sliceSize);
    var byteArrays = new Array(slicesCount);

    for (var sliceIndex = 0; sliceIndex < slicesCount; ++sliceIndex) {
        var begin = sliceIndex * sliceSize;
        var end = Math.min(begin + sliceSize, bytesLength);

        var bytes = new Array(end - begin);
        for (var offset = begin, i = 0; offset < end; ++i, ++offset) {
            bytes[i] = byteCharacters[offset].charCodeAt(0);
        }
        byteArrays[sliceIndex] = new Uint8Array(bytes);
    }
    return new Blob(byteArrays, { type: contentType });
}

需要切片以避免内存不足错误.

使用jpg和pdf文件(至少这是我测试的).应该与其他mimetypes/contenttypes一起使用.检查您的目标浏览器及其版本,他们需要支持Uint8Array,Blob和atob.

以下是使用Cordova/Android将文件写入设备本地存储的代码:

...
window.resolveLocalFileSystemURL(cordova.file.externalDataDirectory, function(dirEntry) {

                    // Setup filename and assume a jpg file
                    var filename = attachment.id + "-" + (attachment.fileName ? attachment.fileName : 'image') + "." + (attachment.fileType ? attachment.fileType : "jpg");
                    dirEntry.getFile(filename, { create: true, exclusive: false }, function(fileEntry) {
                        // attachment.document holds the base 64 data at this moment
                        var binary = base64toBlob(attachment.document, attachment.mimetype);
                        writeFile(fileEntry, binary).then(function() {
                            // Store file url for later reference, base 64 data is no longer required
                            attachment.document = fileEntry.nativeURL;

                        }, function(error) {
                            WL.Logger.error("Error writing local file: " + error);
                            reject(error.code);
                        });

                    }, function(errorCreateFile) {
                        WL.Logger.error("Error creating local file: " + JSON.stringify(errorCreateFile));
                        reject(errorCreateFile.code);
                    });

                }, function(errorCreateFS) {
                    WL.Logger.error("Error getting filesystem: " + errorCreateFS);
                    reject(errorCreateFS.code);
                });
...

编写文件本身:

function writeFile(fileEntry, dataObj) {
    return $q(function(resolve, reject) {
        // Create a FileWriter object for our FileEntry (log.txt).
        fileEntry.createWriter(function(fileWriter) {

            fileWriter.onwriteend = function() {
                WL.Logger.debug(LOG_PREFIX + "Successful file write...");
                resolve();
            };

            fileWriter.onerror = function(e) {
                WL.Logger.error(LOG_PREFIX + "Failed file write: " + e.toString());
                reject(e);
            };

            // If data object is not passed in,
            // create a new Blob instead.
            if (!dataObj) {
                dataObj = new Blob(['missing data'], { type: 'text/plain' });
            }

            fileWriter.write(dataObj);
        });
    })
}

我使用的是最新的Cordova(6.5.0)和插件版本:

我希望这能使每个人都朝着正确的方向前进.

Answer 3

var src = "data:image/jpeg;base64,";
src += item_image;
var newImage = document.createElement('img');
newImage.src = src;
newImage.width = newImage.height = "80";
document.querySelector('#imageContainer').innerHTML = newImage.outerHTML;//where to insert your image

Answer 4

HTML

<img id="imgElem"></img>

JS

string baseStr64="/9j/4AAQSkZJRgABAQE...";
imgElem.setAttribute('src', "data:image/jpg;base64," + baseStr64);

Answer 5

必须根据@Joseph的答案添加它。如果有人要创建图像对象：

var image = new Image();
image.onload = function(){
   console.log(image.width); // image is loaded and we have image width 
}
image.src = 'data:image/png;base64,iVBORw0K...';
document.body.appendChild(image);