二进制数组到画布

2022-01-17 00:00:00 image canvas javascript html html5-canvas

我想将 jpeg 图像从二进制数组加载到画布(目前正在尝试使用 Uint8Array).我一直在网上寻找解决方案，但我能找到的只是将数组转换为 base64，然后加载效率不高的图像.

I'm would like to load a jpeg image to a canvas from a binary array (currently trying with an Uint8Array). I've been looking all over the net for a solution but all I could find is converting the array to base64 and then loading the image which is not very efficient.

这是我用于加载图像的代码:

Here is my code used for loading the image:

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<canvas id="MainImage" width="756" height="600">Your browser doesn't support html5</canvas>
<script type="text/javascript">
_Request = new XMLHttpRequest();
var url = "http://localhost/AAA/S.jpg";
try {
   _Request.onreadystatechange = function() {
      if (_Request.readyState == 4 && _Request.status == 200) {
         var downloadedBuffer = _Request.response;
         if (downloadedBuffer) {
            var binaryByteArr = new Uint8Array(downloadedBuffer);
         }
      }
      _Request.open('GET', url, true);
      _Request.responseType = 'arraybuffer';
      _Request.send();
} catch (e) {
}
</script>
</body>
</html>

我想将此处理后的图像数组加载到画布上.

I would like to load this processed array of the image to a canvas.

这只是一个示例，我的原始代码接收一个二进制数组，其中包含多个 jpeg 图像在一个数组中，因此其他方法不起作用.

This is just a sample, my original code receives a binary array with multiple jpeg images in a single array so other methods wont work.

任何帮助将不胜感激

推荐答案

假设您有一种方法可以将二进制数组拆分为每个图像的数组(通过已知长度或使用 JPEG 标头来识别新图像)，您可以使用 Blob 和一个对象 URL:

Assuming you have a way of splitting the binary array into arrays per image (either by a known length or using the JPEG header to identify the new image) you can use Blob and an object URL:

示例(基于 这个来自 MDN 的示例):

var imageData = GetTheTypedArraySomehow();
var blob = new Blob([imageData], {type: "image/jpeg"});
var url = URL.createObjectURL(blob);

现在您可以将图像的 url 设置为 src::

Now you can set the url as src for an image::

var img = new Image();
img.onload = function() {
    /// draw image to canvas
    context.drawImage(this, x, y);
}
img.src = url;

相关文章