saveFile (picData) {
    if (CC_JSB) {
        let filePath = jsb.fileUtils.getWritablePath() + 'render_to_sprite_image.png';
        let success = jsb.saveImageData(picData, this._width, this._height, filePath)
        if (success) {
            cc.log("save image data success, file: " + filePath);
        else {
            cc.error("save image data failed!");
得到的picData其实是一个 Unit8Array 数据类型，请问如何将它保存为一个有效的 png Base64编码呢？
已经尝试过下面方法，但是都不能直接显示为一张PNG图
 * Uint8Array 转 string
static Uint8ArrayToString(unit8Array: Uint8Array): string {
    let CHUNK_SZ = 0x8000;
    let chars = [];
    for (let i = 0; i < unit8Array.length; i += CHUNK_SZ) {
        chars.push(String.fromCharCode.apply(null, unit8Array.subarray(i, i + CHUNK_SZ)));
    return chars.join("");
// 用 js-base64 库去编码
let baseForNative = "data:image/png;base64," + Base64.btoa(Uint8ArrayToString(picData));
// 用浏览器原生API 去编码
let base64ForWeb = "data:image/png;base64," + btoa(Uint8ArrayToString(picData));
得出的两个编码都不能正常解码出可以显示的png图片，感觉应该不是Base64编码问题，因该是 picData 应该要做点什么处理在去编码为Base64吗？
求助~~~~
          
getBase64(unit8Array)

let keyStr = “ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=”;

var output = “”;

var chr1, chr2, chr3, enc1, enc2, enc3, enc4;

var i = 0;

while (i < unit8Array.length) {

chr1 = unit8Array[i++];

chr2 = unit8Array[i++];

chr3 = unit8Array[i++];
        enc1 = chr1 >> 2;
        enc2 = (chr1 & 3) << 4 | chr2 >> 4;
        enc3 = (chr2 & 15) << 2 | chr3 >> 6;
        enc4 = chr3 & 63;
        if (isNaN(chr2)) {
            enc3 = enc4 = 64;
        } else if (isNaN(chr3)) {
            enc4 = 64;
        output = output + keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) + keyStr.charAt(enc4);
    return output;
          
终于解决，这里jsbData的字节流不是png编码，先保存一次，在读出来，转Base64就对了

function uint8ToBase64String(u8a: Uint8Array) {

// 创建一个新的 Uint8Array 来存储字节流

const byteData = new Uint8Array(u8a.buffer);

// 转换为 base64

let binary = ‘’;

for (let i = 0; i < byteData.length; i++) {

binary += String.fromCharCode(byteData[i]);

let base64 = window.btoa(binary);

return base64;

function flipYImage (data: Uint8Array, width: number, height: number) {

// create the data array

let picData = new Uint8Array(width * height * 4);

let rowBytes = width * 4;

for (let row = 0; row < height; row++) {

let srow = height - 1 - row;

let start = srow * width * 4;

let reStart = row * width * 4;

// save the piexls data

for (let i = 0; i < rowBytes; i++) {

picData[reStart + i] = data[start + i];

return picData;

const data = texture.readPixels(pixels, 0, 0, width, height); // texture为RenderTexture对象

var jsbData = flipYImage(data); // 这里需要翻转图片

var tmpFilePath = jsb.fileUtils.getWritablePath() + ‘tmpImg.png’;

jsb.saveImageData(jsbData, width, height, tmpFilePath);

window.fsUtils.readArrayBuffer(tmpFilePath, function (err, byteData: Uint8Array) {

if (!err) {

var b64encoded = uint8ToBase64String(byteData);

console.log(‘isNative base64 len=’, b64encoded.length);

callback && callback(‘data:image/png;base64,’ + b64encoded);

} else {

callback && callback(null);