将字节转换为图像以在HTML5画布上绘制 [英] Converting bytes to an image for drawing on a HTML5 canvas

问题描述

任何人都知道如何将通过websocket（从C＃app）发送的字节转换为图像？然后我想在画布上绘制图像。我可以看到两种方法：

Anyone know how I would convert bytes which are sent via a websocket (from a C# app) to an image? I then want to draw the image on a canvas. I can see two ways of doing this:

• 以某种方式在画布上以字节形式绘制图像而不转换
  它。


• 在javascript中以某种方式将字节转换为base64字符串然后
  draw。

这是我的函数，它接收绘图的字节：

Here's my function which receives the bytes for drawing:

function draw(imgData) {

    var img=new Image();
    img.onload = function() {
        cxt.drawImage(img, 0, 0, canvas.width, canvas.height);
    };

// What I was using before...
img.src = "data:image/jpeg;base64,"+imgData;

}

我之前收到的图像已转换为base64字符串，但在得知发送字节的尺寸较小（小30％？）后，我宁愿让这个工作。我还应该提到图像是jpeg。

I was receiving the image already converted as a base64 string before, but after learning that sending the bytes is smaller in size (30% smaller?) I would prefer to get this working. I should also mention that the image is a jpeg.

任何人都知道我会这样做吗？谢谢您的帮助。 ：）

Anyone know how I would do it? Thanks for the help. :)

推荐答案

我最后用过这个：

function draw(imgData, frameCount) {
    var r = new FileReader();
    r.readAsBinaryString(imgData);
    r.onload = function(){ 
        var img=new Image();
        img.onload = function() {
            cxt.drawImage(img, 0, 0, canvas.width, canvas.height);
        }
        img.src = "data:image/jpeg;base64,"+window.btoa(r.result);
    };
}

我需要在使用btoa（）之前将字节读入字符串。

I needed to read the bytes into a string before using btoa().

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