Accessing a variable within a function in Angular

Recently I started working with Angular and encountered an issue while trying to access a variable inside a function. Below is the code snippet that's causing me trouble:

  mergeImages() {
    var imgurl;
    var canvas: HTMLCanvasElement = this.canvas.nativeElement;
    var context = canvas.getContext('2d');


    let img1 = new Image();
    let img2 = new Image();

    img1.onload = function() {
      canvas.width = img1.width;
      canvas.height = img1.height;
      context.globalAlpha = 1.0;
      img2.src = '../assets/sun.jpg';
    };
    img2.onload = function() {
      context.globalAlpha = 1;
      context.drawImage(img1, 0, 0);
      context.globalAlpha = 0.5; //Remove if pngs have alpha
      context.drawImage(img2, 0, 0);

       imgurl = canvas.toDataURL("image/jpg");
      //console.log(imgurl)

    };
    img1.src = '../assets/moon.jpg';


     }

Now I'm looking for a way to access the "imgurl" from another method.

 printvalue(){
   // Need to access imgurl here
}

Update - The problem lies in Angular not being able to find var a within the printvalue() function as it currently only works inside the function something(). Any suggestions?

angulartypescript

Answer №1

When working with Angular components, it's important to create a scope variable that can be accessed throughout the component. In older versions of AngularJS, you could achieve this using the $scope variable. However, in the latest version of Angular, you need to use this to access variables across the component.

Here is an example:

imgurl: string;
mergeImages() {

    var canvas: HTMLCanvasElement = this.canvas.nativeElement;
    var context = canvas.getContext('2d');

    let img1 = new Image();
    let img2 = new Image();

    img1.onload = () => {
      canvas.width = img1.width;
      canvas.height = img1.height;
      context.globalAlpha = 1.0;
      img2.src = '../assets/sun.jpg';
    };
    img2.onload = () => {
      context.globalAlpha = 1;
      context.drawImage(img1, 0, 0);
      context.globalAlpha = 0.5; // Remove if PNGs have alpha
      context.drawImage(img2, 0, 0);

      this.imgurl = canvas.toDataURL("image/jpg");
      // console.log(imgurl)
    };
    this.img1.src = '../assets/moon.jpg';
}

Answer №2

Modify your code in the following manner

let imageUrl;
blendImages() {

    var canvasElem: HTMLCanvasElement = this.canvas.nativeElement;
    var ctx = canvasElem.getContext('2d');

    let image1 = new Image();
    let image2 = new Image();

    image1.onload = () => {
      canvasElem.width = image1.width;
      canvasElem.height = image1.height;
      ctx.globalAlpha = 1.0;
      image2.src = '../assets/sun.jpg';
    };
    image2.onload = () => {
      ctx.globalAlpha = 1;
      ctx.drawImage(image1, 0, 0);
      ctx.globalAlpha = 0.5; // Remove if pngs have alpha
      ctx.drawImage(image2, 0, 0);

       this.imageUrl = canvasElem.toDataURL("image/jpg");
      //console.log(imageUrl)

    };
    this.image1.src = '../assets/moon.jpg';
}

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