將base64轉換為Javascript文件

Question

目標是將base64字符串轉換為可發送的jpg文件，我不能使用html輸入類型的文件，但我必須以相同的格式提供服務。 我對文件生成有些迷失。 （我在客戶端移動應用程序上）。

這就是我所擁有的：

 file = "data:image/jpg;base64,#{imageData}"

imageData是base64字符串

有沒有辦法將其轉換為有效文件？

Answer 1

免責聲明 ：產生無效結果（關閉，但無效）

我上周早些時候做了相反的事情-也就是說，將圖像作為二進制數據加載（以避開從本地主機運行文件的要求）。

在其中：

加載文件
base64轉換了它
在base64字符串中添加了前同步碼
將構造的字符串設置為img元素的src

這工作得很好。 讀完您的問題后，我試圖簡單地逆轉這一過程。 但是，我在某個地方不成功。 數據是從圖像中正確提取的，然后在某處（我認為在對atob的調用中將其取消編碼），數據被弄亂了。

保存的文件的大小超出預期，在“％PNG”之前添加了字符，並且文件中間缺少一些數據。 老實說，我現在很困惑。

無論如何，這是我嘗試過的代碼：

1.讀取文件並將數據填充到元素中的代碼

// fileVar is an object as returned by <input type='file'>
// imgElem is an <img> element - (doesn't need to be added to the DOM)
function loadImgFromFile(fileVar, imgElem)
{
    var fileReader = new FileReader();
    fileReader.onload = onFileLoaded;
    fileReader.readAsBinaryString(fileVar);
    function onFileLoaded(fileLoadedEvent)
    {
        var result,data;
        data = fileLoadedEvent.target.result;
        result = "data:";
        result += fileVar.type;
        result += ";base64,";
        result += btoa(data);
        imgElem.src = result;
    }
}

2.嘗試從圖像/畫布中獲取數據，並使用程序員提供的文件名強制下載。

<!doctype html>
<html>
<head>
<script>
function byId(e){return document.getElementById(e)}
function newEl(tag){return document.createElement(tag)}
window.addEventListener('load', onPageLoaded, false);

function onPageLoaded(evt)
{
    var imgElem = byId('srcImg');
    imgElem.onload = function(){saveImgAsFile( byId('srcImg'), "myImage.png" );};

        // simple result of canvas.toDataURL() called on a 5x5 pixel image of a '+'
    imgElem.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHklEQVQIW2NkQID/QCYjiAsmoABFEMRBAThVYmgHAAhoBQWHhfyYAAAAAElFTkSuQmCC"; 

    // use the below line instead of the one above, if you wish to assign an actual image file, rather than the result of call to canvas.toDataURL()
    // the base64 string allows me to keep it all in the one file, also, to run if opened via a double-click, rather than having to run from localhost
//  imgElem.src = "img/1x1.png";
}

function saveImgAsFile(imgElem, fileName)
{
    // get a base64 encoded string from an image element
    var srcElem = imgElem;
    var dstCanvas = newEl('canvas');
    dstCanvas.width = srcElem.naturalWidth;
    dstCanvas.height = srcElem.naturalHeight;
    var ctx = dstCanvas.getContext('2d');
    ctx.drawImage(srcElem,0,0);
    var imgSrcStr = dstCanvas.toDataURL();

    // extract the image type
    var colonPos = imgSrcStr.indexOf(":");
    var semiColonPos = imgSrcStr.indexOf(";");
    var imgType = imgSrcStr.slice(colonPos+1, semiColonPos);
    console.log("image type: " + imgType);

    // extract the image data
    var commaPos = imgSrcStr.indexOf(',');
    var base64ImgString = imgSrcStr.slice(commaPos + 1);
    console.log("Data: " + base64ImgString);

    // holds the data that is actually written to disk for this image
    //** I think the error occurs during this step **//
    var unencodedImage = atob(base64ImgString);

    var imgFileAsBlob = new Blob( [unencodedImage], {type: imgType} );
    var fileNameToUse = fileName;

    var downloadLink = newEl('a');
    downloadLink.download = fileNameToUse;
    downloadLink.innerHTML = "Download File";
    if (window.webkitURL != null)
    {
        // Chrome allows the link to be clicked
        // without actually adding it to the DOM.
        downloadLink.href = window.webkitURL.createObjectURL(imgFileAsBlob);
    }
    else
    {
        // Firefox requires the link to be added to the DOM
        // before it can be clicked.
        downloadLink.href = window.URL.createObjectURL(imgFileAsBlob);
        downloadLink.onclick = destroyClickedElement;
        downloadLink.style.display = "none";
        document.body.appendChild(downloadLink);
    }
    downloadLink.click();
}

/*

function saveTextAsFile()
{
    var textToWrite = "This is just some random content";
    var textFileAsBlob = new Blob([textToWrite], {type:'text/plain'})
    var fileNameToSaveAs = "myFile.txt";

    var downloadLink = document.createElement("a");
    downloadLink.download = fileNameToSaveAs;
    downloadLink.innerHTML = "Download File";
    if (window.webkitURL != null)
    {
        // Chrome allows the link to be clicked
        // without actually adding it to the DOM.
        downloadLink.href = window.webkitURL.createObjectURL(textFileAsBlob);
    }
    else
    {
        // Firefox requires the link to be added to the DOM
        // before it can be clicked.
        downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
        downloadLink.onclick = destroyClickedElement;
        downloadLink.style.display = "none";
        document.body.appendChild(downloadLink);
    }
    downloadLink.click();
}
*/
function destroyClickedElement(event)
{
    document.body.removeChild(event.target);
}
</script>
</head>
<body>
    <img id='srcImg'/>
</body>
</html>

將base64轉換為Javascript文件

問題描述

1 個解決方案

解決方案1
2 2014-03-23 12:26:41

將base64轉換為Javascript文件

問題描述

1 個解決方案

解決方案1 2 2014-03-23 12:26:41

解決方案1
2 2014-03-23 12:26:41