Question

简介：

我正在读取智能卡中指纹的图像数据，如您所知，此数据另存为智能卡中的原始图像。我正在开发一个客户端程序，它只使用java脚本从读卡器的扫描仪读取图像并在客户端页面中显示。

现在我的问题：

如何将原始数据的十六进制字符串转换为十六进制字符串，该字符串使用位图图像的相应标头完成？请注意，我的图片有width和height。

尝试过的方法：

我已经通过get buffered image from raw data在java中开发了这个程序。此外，我可以通过Hex2Base64将位图图像的十六进制字符串转换为base64，然后我可以通过base64AsImage在图像标记中显示base64字符串。但是，当且仅当十六进制包含标题时，这些函数才能正常工作，而我们的数据是原始的。

我的代码（仅适用于包含标题的Hex String）：

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>

    <script>
        if (!window.atob) {
            var tableStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
            var table = tableStr.split("");

            window.atob = function (base64) {
                if (/(=[^=]+|={3,})$/.test(base64)) throw new Error("String contains an invalid character");
                base64 = base64.replace(/=/g, "");
                var n = base64.length & 3;
                if (n === 1) throw new Error("String contains an invalid character");
                for (var i = 0, j = 0, len = base64.length / 4, bin = []; i < len; ++i) {
                    var a = tableStr.indexOf(base64[j++] || "A"), b = tableStr.indexOf(base64[j++] || "A");
                    var c = tableStr.indexOf(base64[j++] || "A"), d = tableStr.indexOf(base64[j++] || "A");
                    if ((a | b | c | d) < 0) throw new Error("String contains an invalid character");
                    bin[bin.length] = ((a << 2) | (b >> 4)) & 255;
                    bin[bin.length] = ((b << 4) | (c >> 2)) & 255;
                    bin[bin.length] = ((c << 6) | d) & 255;
                };
                return String.fromCharCode.apply(null, bin).substr(0, bin.length + n - 4);
            };

            window.btoa = function (bin) {
                for (var i = 0, j = 0, len = bin.length / 3, base64 = []; i < len; ++i) {
                    var a = bin.charCodeAt(j++), b = bin.charCodeAt(j++), c = bin.charCodeAt(j++);
                    if ((a | b | c) > 255) throw new Error("String contains an invalid character");
                    base64[base64.length] = table[a >> 2] + table[((a << 4) & 63) | (b >> 4)] +
                    (isNaN(b) ? "=" : table[((b << 2) & 63) | (c >> 6)]) +
                    (isNaN(b + c) ? "=" : table[c & 63]);
                }
                return base64.join("");
            };

        }

        function hexToBase64(str) {
            return btoa(String.fromCharCode.apply(null,
                            str.replace(/\r|\n/g, "").replace(/([\da-fA-F]{2}) ?/g, "0x$1 ").replace(/ +$/, "").split(" "))
            );
        }

        function base64ToHex(str) {
            for (var i = 0, bin = atob(str.replace(/[ \r\n]+$/, "")), hex = []; i < bin.length; ++i) {
                var tmp = bin.charCodeAt(i).toString(16);
                if (tmp.length === 1) tmp = "0" + tmp;
                hex[hex.length] = tmp;
            }
            return hex.join(" ");
        }
        function doConvert() {
            var myHex =  document.getElementById('myText').value;
            var myBase64 = hexToBase64(myHex);
            document.getElementById('myImage').src = "data:image/bmp;base64," +  myBase64;
        }
    </script>



</head>
<body>
<div>
    <p>
        Enter Raw Hex:
        <br>
        <textarea rows="4" cols="50" id="myText">Enter Raw Hex String here ...</textarea>
        <br>
        <button id="myButton" onclick="doConvert()"> Click me </button>
        <br>
        <img id="myImage" alt="img1"/>
    </p>
</div>
</body>
</html>

解决了java中问题的part of code：

private static BufferedImage byte2Buffered(byte[] rawData, int width, int height){
    BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_BYTE_GRAY);
    byte[] array = ((DataBufferByte)image.getRaster().getDataBuffer()).getData();
    System.arraycopy(rawData, 0, array, 0, rawData.length);
    return image;
}

请注意，由于JavaScript中没有BufferedImage类型，因此我们无法在JavaScript中使用此方法。

Answer 1

在window.atob方法中，您正在构建一个8位整数数组的字符串（这就是bin[length]正在创建的字符串。）只返回该数组而不是字符串。

然后，如果您必须支持旧浏览器，则需要将每个像素分别写入画布。但是，如果您可以定位现代浏览器，只需构建一个Uint8ClampedArray，将其放入ImageData对象，并将putImageData()放入画布。

下面是一些工作示例代码。我正在使用随机字节（data）填充虚拟数组，但您将使用从atob返回的字节数组。

var canvas = document.querySelector('canvas'),
    ctx = canvas.getContext('2d'),
  width = canvas.width,
  height = canvas.height,
  pixelLength = width * height,
  data,
  imageData;

// You can use any kind of array, including a
// Uint8ClampedArray, since it is just going to be
// crammed into a clamped array anyway. I'm using a
// Uint8Array just as an example.
data = new Uint8Array(pixelLength);

// Create an array of random data
data = data.map(function (btye) { return Math.floor(Math.random() * 256); });

// The source data is 8-bit grayscale, but it needs 
// to be 32-bit RGBA in a Uint8ClampedArray. The
// structure is simple. For every byte of the gray-
// scale array, write out three copies of that byte 
// and then `256` as 100% opaque.
data = data.reduce(function (carry, current, index) {
    var baseIndex = index * 4;

  carry[baseIndex] = current;
    carry[baseIndex + 1] = current;
    carry[baseIndex + 2] = current;
    carry[baseIndex + 3] = 256;

return carry;
}, new Uint8ClampedArray(pixelLength * 4));

// The Uint8ClampedArray can now be used to build the image
imageData = new ImageData(data, width, height);
ctx.putImageData(imageData, 0, 0);

在JavaScript中将原始图像的十六进制字符串转换为位图图像

1 个答案: