[英]React: Display an image converted to base64
我很难显示由我的 Node/Express 服务器发送到我的 React 应用程序的图像。 我尝试仔细阅读其他 SO 问题中的解决方案,但我无法让它发挥作用。 这是我的步骤
router.get('/:file_id', (req, res) => {
//... Query file information //
const filePath = `${config.FILE_STORAGE}/${doc._id}`;
res.sendFile(filePath);
});
axiosInstance.get(`/files/${document.file}`)
.then((response) => {
const image_base64 = Buffer.from(response.data).toString('base64');
setThumbnail(image_base64);
})
img
标签中<img src={`data:image/jpg;base64,${thumbnail}`}
但图像不显示。 我做了一些额外的验证:
<img>
手动插入了一张我使用在线转换器进行 base64 编码的图像,并显示出来。您可以使用此函数生成base64
字符串。 这对我来说可以。 函数如下:
function base64ArrayBuffer(byteArray) {
var base64 = "";
var encodings =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var bytes = byteArray;
var byteLength = bytes.byteLength;
var byteRemainder = byteLength % 3;
var mainLength = byteLength - byteRemainder;
var a, b, c, d;
var chunk;
// Main loop deals with bytes in chunks of 3
for (var i = 0; i < mainLength; i = i + 3) {
// Combine the three bytes into a single integer
chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
// Use bitmasks to extract 6-bit segments from the triplet
a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
b = (chunk & 258048) >> 12; // 258048 = (2^6 - 1) << 12
c = (chunk & 4032) >> 6; // 4032 = (2^6 - 1) << 6
d = chunk & 63; // 63 = 2^6 - 1
// Convert the raw binary segments to the appropriate ASCII encoding
base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
}
// Deal with the remaining bytes and padding
if (byteRemainder == 1) {
chunk = bytes[mainLength];
a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
// Set the 4 least significant bits to zero
b = (chunk & 3) << 4; // 3 = 2^2 - 1
base64 += encodings[a] + encodings[b] + "==";
} else if (byteRemainder == 2) {
chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1];
a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
b = (chunk & 1008) >> 4; // 1008 = (2^6 - 1) << 4
// Set the 2 least significant bits to zero
c = (chunk & 15) << 2; // 15 = 2^4 - 1
base64 += encodings[a] + encodings[b] + encodings[c] + "=";
}
return base64;
}
所以,在你的情况下,代码应该是:
axiosInstance.get(`/files/${document.file}`)
.then((response) => {
const image_base64 = base64ArrayBuffer(Buffer.from(response.data));
setThumbnail(image_base64);
})
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