How to pass a parameter for image transformations

I want to get an image from a blob. And I want to pass the parameter imageToShow in createImageFromBlob , but the function does not see it

Where is the error?

imageToShow: any;
    
...
this.createImageFromBlob(data, this.imageToShow);
...


createImageFromBlob(image: Blob, imageToShow: any) {
  let reader = new FileReader();
  reader.onload = () => {
    imageToShow = reader.result;
  };
  reader.readAsDataURL(image);
}