将字节转换为图像以在 HTML5 画布上绘图

Converting bytes to an image for drawing on a HTML5 canvas(将字节转换为图像以在 HTML5 画布上绘图)

问题描述

有人知道我如何将通过 websocket(从 C# 应用程序)发送的字节转换为图像吗?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:

• 不知何故以字节形式在画布上绘制图像而不转换它.
• 然后在javascript中以某种方式将字节转换为base64字符串画.

这是我接收绘图字节的函数:

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经转换为 base64 字符串，但在得知发送字节的大小更小(小 30%?)之后，我更愿意让它工作.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.

有人知道我会怎么做吗?谢谢您的帮助.:)

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

推荐答案

我最后用了这个:

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);
    };
}

在使用 btoa() 之前，我需要将字节读入字符串.

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

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