javascript - How to save an image to localStorage and display it on the next page?

Question

So, basically, I need to upload a single image, save it to localStorage, then display it on the next page.

Currently, I have my HTML file upload:

<input type='file' id="uploadBannerImage" onchange="readURL(this);" />

Which uses this function to display the image on the page

function readURL(input) 
{
    document.getElementById("bannerImg").style.display = "block";

    if (input.files && input.files[0]) {
        var reader = new FileReader();

        reader.onload = function (e) {
            document.getElementById('bannerImg').src =  e.target.result;
        }

        reader.readAsDataURL(input.files[0]);
    }
}

The image is displayed instantly on the page for the user to see. They are then asked to fill out the rest of the form. This part is working perfectly.

Once the form is complete, they then press a 'Save' button. Once this button is pressed, I save all form inputs as localStorage strings. I need a way to also save the image as a localStorage item.

The save button will also direct them to a new page. This new page will display the users data in a table, with the image being at the top.

So plain and simple, I need to save the image in localStorage once the 'Save' button is pressed, and then loan the image on the next page from localStorage.

I found some solutions such as this fiddle and this article at moz://a HACKS.

Although I am still extremely confused on how this works, and I only really need a simple solution. Basically, I just need to find the image via getElementByID once the 'Save' button is pressed, and then process and save the image.

Answer 1

To whoever also needs this problem solved:

Firstly, I grab my image with getElementByID, and save the image as a Base64. Then I save the Base64 string as my localStorage value.

bannerImage = document.getElementById('bannerImg');
imgData = getBase64Image(bannerImage);
localStorage.setItem("imgData", imgData);

Here is the function that converts the image to a Base64 string:

function getBase64Image(img) {
    var canvas = document.createElement("canvas");
    canvas.width = img.width;
    canvas.height = img.height;

    var ctx = canvas.getContext("2d");
    ctx.drawImage(img, 0, 0);

    var dataURL = canvas.toDataURL("image/png");

    return dataURL.replace(/^data:image/(png|jpg);base64,/, "");
}

Then, on my next page I created an image with a blank src like so:

<img src="" id="tableBanner" />

And straight when the page loads, I use these next three lines to get the Base64 string from localStorage, and apply it to the image with the blank src I created:

var dataImage = localStorage.getItem('imgData');
bannerImg = document.getElementById('tableBanner');
bannerImg.src = "data:image/png;base64," + dataImage;

Tested it in quite a few different browsers and versions, and it seems to work quite well.