How to encode image (asset) and via photo picker to base64 in React Native (iOS)?

问题

I've been struggling to find a supported solution to encode images (from assets) and photo picker to base64string.

I can do this via Swift in a straight native app.

func convertImageTobase64(format: ImageFormat, image:UIImage) -> String? {
var imageData: Data?
switch format {
case .png: imageData = image.pngData()
case .jpeg(let compression): imageData = image.jpegData(compressionQuality: compression)
}
return imageData?.base64EncodedString()

}

var mylogo: UIImage? = UIImage.init(named: "DFU-180x180")
let base64String = convertImageTobase64(format: .png, image: mylogo!)
let dataString = "data:image/jpg;base64," + base64String!

I tried to do this via NativeModules, but I get errors for RCTConvert being run on background thread instead of main. Images.h

#import <Foundation/Foundation.h>
#import <React/RCTBridgeModule.h>


@interface Images : NSObject <RCTBridgeModule>
@end

Images.m

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import "Images.h"

@implementation Images
RCT_EXPORT_MODULE()

// All the methods are implemented in a Swift extension, see FileBridgeExtension.swift
RCT_EXTERN_METHOD(convertImageTobase64:(nonnull NSString*)format image:(nonnull UIImage*)image callback:(RCTResponseSenderBlock))

@end

ImagesExtension.swift

import UIKit

public enum ImageFormat {
    case png
    case jpeg(CGFloat)
}

@objc extension Images {

    @objc func convertImageTobase64(_ format: NSString, image:UIImage, callback: @escaping ([Any]?)->Void) {
        var imageData: Data?
        print("convertImageTobase64_line 1")
        print("convert format: " + (format as! String))
        switch format {
        case ".png": imageData = UIImagePNGRepresentation(image)
        print("convertImageTobase64_line 2")
        case ".jpeg": imageData = UIImageJPEGRepresentation(image, 1.0)
        print("convertImageTobase64_line 3")
        default:
            print("convertImageTobase64_line 4")
            let error = RCTMakeError("Invalid image format", nil, nil)
            callback([[error], []]);
        }
        let base64string = imageData?.base64EncodedString()
        print("convertImageTobase64_line 5 = " + base64string!)
        callback([[NSNull()], [base64string]]);
    }

}

I've tried 4 different React Native libraries and nothing works. I get errors that the library doesn't exist, even thought I do the npm install and confirm the library exists in node_modules. I even remove the node_modules folder, and rebuild it with npm install.

2 of the libraries that I've tried.

npm version that I'm using is: 6.4.1 node version that I'm using is: 8.12.0 Xcode v10 react-native-image-base64

react-native-image-to-base64