Blob constructor browser compatibility

问题:

I am developping an application where I recieve image data stored in a uint8Array. I then transform this data to a Blob and then build the image url.

Simplified code to get data from server:

var array;

var req = new XMLHttpRequest();
var url = "img/" + uuid + "_" +segmentNumber+".jpg";
req.open("GET", url, true);
req.responseType = "arraybuffer";
req.onload = function(oEvent) {
    var data = req.response;    
    array = new Int8Array(data);      
};

Constructor:

out = new Blob([data], {type : datatype} );

The Blob contsructor is causing problem. It works fine on all browsers except Chrome on mobile and desktop devices.

Use of Blob:

// Receive Uint8Array using AJAX here
// array = ...
// Create BLOB
var jpeg = new Blob( [array.buffer], {type : "image/jpeg"});
var url = DOMURL.createObjectURL(jpeg);
img.src = url;

Desktop Chrome gives me a warnning : ArrayBuffer values are deprecated in Blob Constructor. Use ArrayBufferView instead.

Mobile Chrome gives me an error: illegal constructor

If I change the constructor to work on Chrome it fails on other browsers.

回答1:

So, these are actually two different problems. The Desktop Chrome warning was a bug in chrome which is fixed since 2013-03-21.

Mobile Chrome is giving you a TypeError because the blob constructor is not supported. Instead you must use the old BlobBuilder API. The BlobBuilder API has browser specific BlobBuilder constructors. This is the case for FF6 - 12, Chrome 8-19, Mobile Chrome, IE10 and Android 3.0-4.2.

var array = new Int8Array([17, -45.3]);

try{
  var jpeg = new Blob( [array], {type : "image/jpeg"});
}
catch(e){
    // TypeError old chrome and FF
    window.BlobBuilder = window.BlobBuilder || 
                         window.WebKitBlobBuilder || 
                         window.MozBlobBuilder || 
                         window.MSBlobBuilder;
    if(e.name == 'TypeError' && window.BlobBuilder){
        var bb = new BlobBuilder();
        bb.append(array.buffer);
        var jpeg = bb.getBlob("image/jpeg");
    }
    else if(e.name == "InvalidStateError"){
        // InvalidStateError (tested on FF13 WinXP)
        var jpeg = new Blob( [array.buffer], {type : "image/jpeg"});
    }
    else{
        // We're screwed, blob constructor unsupported entirely   
    }
}

Fiddle: http://jsfiddle.net/Jz8U3/13/

回答2:

Got it working with your code. I only had to change some little detail:

if(e.name == 'TypeError' && window.BlobBuilder){
        var bb = new BlobBuilder();
        bb.append(data);
        out = bb.getBlob(datatype);
        console.debug("case 2");
    }

bb.append(data); // data must be with no brackets

My function(constructor) that works now for all browsers:

var NewBlob = function(data, datatype)
{
    var out;

    try {
        out = new Blob([data], {type: datatype});
        console.debug("case 1");
    }
    catch (e) {
        window.BlobBuilder = window.BlobBuilder ||
                window.WebKitBlobBuilder ||
                window.MozBlobBuilder ||
                window.MSBlobBuilder;

        if (e.name == 'TypeError' && window.BlobBuilder) {
            var bb = new BlobBuilder();
            bb.append(data);
            out = bb.getBlob(datatype);
            console.debug("case 2");
        }
        else if (e.name == "InvalidStateError") {
            // InvalidStateError (tested on FF13 WinXP)
            out = new Blob([data], {type: datatype});
            console.debug("case 3");
        }
        else {
            // We're screwed, blob constructor unsupported entirely   
            console.debug("Errore");
        }
    }
    return out;
}