How to store and retrieve image to localStorage?

javascript cordova jquery-mobile canvas html5-canvas

26,023

Here the complete solution using File Api


    <html>
    <body>
    <input type="file" id="image-input" />
    <img id="image-container" />
    <script type="text/javascript">
    (function(){
          /** @type {Node} */
      var imgInput = document.getElementById( "image-input" ),
          /** @type {Node} */
          imgContainer = document.getElementById( "image-container" ),
          /** Restore image src from local storage */
          updateUi = function() {
            imgContainer.src = window.localStorage.getItem( "image-base64" );
          },
          /** Register event listeners */
          bindUi = function(){
            imgInput.addEventListener( "change", function(){
              if ( this.files.length ) {
                var reader = new FileReader();
                reader.onload = function( e ){
                  window.localStorage.setItem( "image-base64", e.target.result );
                  updateUi();
                };
                reader.readAsDataURL( this.files[ 0 ] );
              }
            }, false );
          };

    updateUi();
    bindUi();
    }());
    </script>
    </body>
    </html>

26,023

Author by

Ed Jones

Learning web programming from scratch somewhere 70 miles from a city with programmers...wasn't perhaps my brightest idea.

Updated on April 19, 2020

Comments

Ed Jones about 4 years

Thought I had this, but no. The goal: snap a photo (insurance card), save it locally, and retrieve it later.

// Get a reference to the image element
var elephant = document.getElementById("SnapIt_mobileimage_5");

var imgCanvas = document.createElement("canvas"),
imgContext = imgCanvas.getContext("2d");

// Make sure canvas is as big as the picture
imgCanvas.width = elephant.width;
imgCanvas.height = elephant.height;

// Draw image into canvas element

imgContext.drawImage(elephant, 0, 0, elephant.width, elephant.height );
 console.log( 'Did that' );
// Get canvas contents as a data URL
var imgAsDataURL = imgCanvas.toDataURL("data:image/jpg;base64,");

// Save image into localStorage
try {
localStorage.setItem("elephant", imgAsDataURL);
}
catch (e) {
console.log("Storage failed: " + e);
}; 

//Did it work?
var pic = localStorage.getItem("elephant");

console.log( elephant );
console.log( pic );

Each step succeeds, the final output is:

<img id="SnapIt_mobileimage_5" class=" SnapIt_mobileimage_5" name="mobileimage_5" dsid="mobileimage_5" src="files/views/assets/image/IMG_0590.JPG">
 data:image/png;base64,iVBORw0KGgoAAAANSUhEUgA

On a new page, when I ask

var policy_shot = localStorage.getItem( 'elephant' );
console.log( policy_shot );

$('#TestScreen_mobileimage_1').src = policy_shot ;

It logs the binary:

data:image/png;base64,iVBORw0KGgoAAAANSUhEUg ....

But the image doesn't appear.

Is there a simpler approach?
Why is the getItem (binary) preceded by data:image/png; instead of data:image/jpg ?
Is that why it doesn't display, or am I doing something else wrong?