[英]Decoding Image Base64 String not working
我需要一種從客戶端壓縮所選圖像,然后將其發送到服務器的方法,我在img.onload中想到了以下代碼:
var canvas = document.createElement('canvas');
var img = document.createElement("img");
img.src = url;
var width = img.width;
var height = img.height;
if (width > height) {
if (width > max_width) {
//height *= max_width / width;
height = Math.round(height *= max_width / width);
width = max_width;
}
} else {
if (height > max_height) {
width = Math.round(width *= max_height / height);
height = max_height;
}
}
canvas.width = width;
canvas.height = height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0, width, height);
var base64 = canvas.toDataURL("image/jpeg");
然后我使用ajax發送base64,如下所示:
function sendImage(base64){
var query = "number=0&id=012&base64="+base64;
var url = "myImage.jsp";
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = postImgAjax;
xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlHttp.setRequestHeader("Content-length", query.length);
xmlHttp.setRequestHeader("Connection", "close");
xmlHttp.send(query);
}
在myImage.jsp中,我使用以下代碼對Base64字符串進行解碼:
String imgBase64 = request.getParameter("base64");
//BASE64Decoder d = new BASE64Decoder();
String str = (imgBase64.split(",")[1]);
//str = str.replaceAll(" ", "");
//System.out.println("\n "+str.replaceAll("\n", ""));
byte[] imgBytes = Base64.decodeBase64(str.getBytes());
//d.decodeBuffer(str.replaceAll("\\s", ""));
//DatatypeConverter.parseBase64Binary(str.replaceAll("\\s", ""));
Utils.save(imgBytes);
我花了幾個小時嘗試使之工作,我嘗試了許多可能性(例如使用不同的解碼器包,刪除空格等),它不斷拋出javax.imageio.IIOException:無效的JPEG文件結構:兩個SOF標記或兩個soi和等等。它很少寫入字節,但是圖像每次都損壞,它顯示的是灰色圖像而不是原始圖像。
我解決了 我需要做的是使用javascript方法encodeURIComponent()對base64進行url編碼。 因此,發送base64字符串的代碼如下所示:
function sendImage(base64){
var query = "number=0&id=012&base64="+encodeURIComponent(base64);
var url = "myImage.jsp";
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = postImgAjax;
xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlHttp.setRequestHeader("Content-length", query.length);
xmlHttp.setRequestHeader("Connection", "close");
xmlHttp.send(query);
}
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