An example of how you might implement the long press of an image to save it

touchAndSaveImage.ux

<template>
  <div class="doc-page">
    <div class="page-title-wrap">
      <text class="page-title">{{componentName}}</text>
    </div>
    <div class="item-container">
      <text class="item-title">Remote
        image:https://tse1-mm.cn.bing.net/th/id/OIP.QFyNrABM6FhaY_0TCuUZqgHaFj?pid=Api&rs=1</text>
      <div class="item-content">
        <image src="https://tse1-mm.cn.bing.net/th/id/OIP.QFyNrABM6FhaY_0TCuUZqgHaFj?pid=Api&rs=1" id="image" style="object-fit:cover" onlongpress="onImageLongpress"></image>
      </div>
    </div>
  </div>
</template>
<style>
  .doc-page {
    flex: 1;
    flex-direction: column;
  }
  .item-container {
    margin-top: 40px;
    margin-bottom: 40px;
    flex-direction: column;
  }
  .item-title {
    padding-left: 30px;
    padding-bottom: 20px;
    color: #aaaaaa;
  }
  .item-content {
    height: 200px;
    justify-content: center; 
  }
  #image {
    width: 240px;
    height: 160px;
    object-fit: contain;
  }
</style>
<script>
import prompt from'@system.prompt'
import media from '@system.media'
export default{
  private: {
componentName:"Touch and hold the following image to save it",
    inputImageURL: 'https: //tse1-mm.cn.bing.net/th/id/OIP.QFyNrABM6FhaY_0TCuUZqgHaFj?pid=Api&rs=1'
  },
  onInit(){
This.$page.setTitleBar({text:'Example of touching and holding an image to save it'});
  },
  onImageLongpress(){
        var that=this;
    prompt.showDialog({
message:'Do you want to save the picture?',
      buttons: [{
        text: 'OK',
        color: '#33dd44'
      },
      {
        text: 'Cancel',
        color: '#33dd44'
      }],
      success: function(data){
                console.log("handling callback",data);
                if(data.index===0)
                {
                    that.$element("image").toTempFilePath({
                        fileType: 'jpg', 
                        quality: 1.0, 
                        success: function (ret) {
                            console.log('toTempFilePath success:tempFilePath=' + ret.tempFilePath)
                            media.saveToPhotosAlbum ({
                                uri: ret.tempFilePath,
                                success:function(data)
                                {
                                    console.log("save picture success");
                                },
                                fail: function(data, code) {
                                    console.log("handling fail, code=" + code);
                                }
                            })
                        }, 
                        fail: function (msg, code) {
                            console.log('toTempFilePath failed:code=' + code + '; msg=' + msg);
                        }, complete: function (ret) {
                            console.log('toTempFilePath complete');
                        }
                    })
                }
      },
      cancel: function(){
        console.log("cancel");
      }
    })
  }
}
</script>