Saving an image (retrieved from external library) locally - Angular?

问题

I'm really really new to Angular and all. So I've gotten a QR code image from a library (angularx-qrcode) generator.

Here's the code to get the image:

     <qrcode [qrdata]="'Your QR code data string'" [size]="256" [level]="'M'"></qrcode>

Now I wanna have a button that allows the user to save the above image locally. How can I achieve this?

Also is the syntax different for different Angular versions (e.g. 2 vs 7)?

Thank you so much!! any help would be appreciated:)

回答1:

Now I wanna have a button that allows the user to save the above image locally. How can I achieve this?

So, you want to download the Qr code image into your local device

CHECK WORKING STACKBLITZ

This is my approach on how I did it!

First, you need to get the base64 image data from the generated image

Convert the base 64 encoded image into blob data

Add a button to download the image

Your component.html can be something like this:~

<qrcode #parent [qrdata]="qrdata" [size]="256" [level]="'M'"></qrcode>
<br>
<button (click)="saveAsImage(parent)">Download QR Code Image</button>

Your component.ts can be something like this:~

import { Component } from '@angular/core';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  qrdata = 'Initial QR code data string';

  saveAsImage(parent) {
    // fetches base 64 date from image
    const parentElement = parent.el.nativeElement.querySelector("img").src;

    // converts base 64 encoded image to blobData
    let blobData = this.convertBase64ToBlob(parentElement);

    // saves as image
    if (window.navigator && window.navigator.msSaveOrOpenBlob) { //IE
      window.navigator.msSaveOrOpenBlob(blobData, 'Qrcode');
    } else { // chrome
      const blob = new Blob([blobData], { type: "image/png" });
      const url = window.URL.createObjectURL(blob);
      // window.open(url);
      const link = document.createElement('a');
      link.href = url;
      link.download = 'Qrcode';
      link.click();
    }

  }

  private convertBase64ToBlob(Base64Image: any) {
    // SPLIT INTO TWO PARTS
    const parts = Base64Image.split(';base64,');
    // HOLD THE CONTENT TYPE
    const imageType = parts[0].split(':')[1];
    // DECODE BASE64 STRING
    const decodedData = window.atob(parts[1]);
    // CREATE UNIT8ARRAY OF SIZE SAME AS ROW DATA LENGTH
    const uInt8Array = new Uint8Array(decodedData.length);
    // INSERT ALL CHARACTER CODE INTO UINT8ARRAY
    for (let i = 0; i < decodedData.length; ++i) {
      uInt8Array[i] = decodedData.charCodeAt(i);
    }
    // RETURN BLOB IMAGE AFTER CONVERSION
    return new Blob([uInt8Array], { type: imageType });
  }

}

Also, if you want to save the text inside the QRCode check this one below:~

CHECK WORKING STACKBLITZ

回答2:

I did not get actually what you want but as i see you want to grab an image from storage and provide it to qrdata and vice versa

Storage in Angular

You might use localStorag

Create a simple service contains the following code

import { Injectable } from '@angular/core';

@Injectable()
export class MemoryService {
  constructor() {}

  set(key: string, data: any): void {
    try {
      localStorage.setItem(key, JSON.stringify(data));
    } catch (e) {
      console.error(e);
    }
  }

  get(key: string) {
    try {
      return JSON.parse(localStorage.getItem(key));
    } catch (e) {
      console.error(e);
      return null;
    }
  }
}

Return back to your qrcode component

// File: example.ts
export class QRCodeComponent {
  public myAngularxQrCode: string = null;
  constructor (private memory: MemoryService) {
    // assign a value
    // this.myAngularxQrCode = 'Your QR code data string';
    // here you need to get the value from storage and assign it to your variable
    this.myAngularxQrCode = this.memory.get('YOUR OWN KEY');
  }

  storeQRData() {
   this.memory.set('YOUR OWN KEY' , this.myAngularxQrCode); 
  }
}

// File: example.html
<qrcode [qrdata]="myAngularxQrCode" [size]="256" [level]="'M'"></qrcode>
<button (click)="storeQRData()">Save To Storage</button>

来源：https://stackoverflow.com/questions/55979501/saving-an-image-retrieved-from-external-library-locally-angular

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