How to render blob image in vue.js stored in database

Question

I am using Vue.js in the front-end. I have Node.js, Express, PostgreSQL (with Sequelize ) on the backend.

I am storing an item in the database that includes a thumbnail image.

Database Model

const Item = sequelize.define('item', {
    id: {
        type: Sequelize.INTEGER,
        primaryKey: true,
        autoIncrement: true
    },
    name: {
        type: Sequelize.TEXT,
        allowNull: false,
    },

    image: {
        type: Sequelize.BLOB('long'),
        allowNull: true,
    },

Database-wise, the image is being stored as a Blob and I think this is fine (and yes, I am aware that it's not best-practice to put images in a database).

I observe in the browser that the object that I am accessing in my Vue template with this.item.image is an Object of the type Buffer.

Adding to Database

I add the item to the database in the browser with this in my vue template:

     <label for="image" class="itemCreate__field itemCreate__field--image">
       <span class="itemCreate__fieldLabel">Image</span>
       <input id="file"  type="file" accept="image/*" @change="onFileChange"/>
        <img v-if="itemPreviewImage" :src="itemPreviewImage" />
     </label>

And that HTML relies on these methods:

     onFileChange(evt) {
        const files = evt.target.files || evt.dataTransfer.files;
        if (!files.length) return;
        this.createImage(files[0]);

    },
    createImage(file) {
        const image = new Image();
        const reader = new FileReader();

        reader.onload = evt => {
            this.itemPreviewImage = evt.target.result;
            this.item.image = evt.target.result;
        }

        reader.readAsDataURL(file);
    },

I have this in the vue template that renders the image:

        <div v-if="item.image">
            <img :src="imgUrl" alt="Picture of item"/>
        </div>

Rendering from Database

I have tried the following approaches, which do not work:

createObjectUrl borrowed from here:

    imgUrl(){
      const objUrl = window.URL.createObjectURL(new Blob(this.item.image.data));

      return objUrl;
    }

Creating a base64 string borrowed from here:

    imgUrl(){
        const intArray = new Uint8Array(this.item.image.data);
        const reducedArray = intArray.reduce((data, byte) => data + String.fromCharCode(byte), '');

        const base64String = `data:image/png;base64, ${btoa(reducedArray)}`;


        return base64String;
    }

Creating a new Uint8Array and then getting an objectUrl (borrowed here):

imgUrl(){
  const arrayBuffer = new Uint8Array(this.item.image);
  const blob  = new Blob([arrayBuffer], {type: "image/png"});

  return window.URL.createObjectURL(blob);

}

In all cases (including some attempts with FileReader), I get broken images. I don't get errors in the console, though.

I think the issue is that I am not submitting correct data to the database.

I am sending an Ajax request that has the File attached as a property, and I should probably convert it to ¿something else?

I was having basically this exact same issue, in the middle of posting another question when I found this one, I got past it by uploading the base64 string as a dataType.TEXT. This does not feel like the right solution but for the small project I'm building not a big deal. Here is a repo with a small working example: postgres pic. master has datatype blob attempted, text-solution has the text solution. — ContextCue
– ContextCue, Commented Jul 27, 2018 at 22:23

Frondor · Accepted Answer · 2018-05-03 16:11:41Z

2

First, be sure you're getting a valid base64 string: https://codebeautify.org/base64-to-image-converter

Then try defining a getter to the Item model

const Item = sequelize.define('item', {
    ...
    image: {
        type: Sequelize.BLOB('long'),
        allowNull: true,
        get () { // define a getter
            const data = this.getDataValue('image')
            return data ? data.toString('base64') : ''
        },
        set(val) {
          this.setDataValue('image', val);
        }
    },
    ...
}

Computed property

imgURL () {
    return this.item.image
        ? 'data:image/png;charset=utf-8;base64,' + this.item.image 
        : '' // some default image

}

edited May 3, 2018 at 16:11

answered May 3, 2018 at 15:25

Frondor

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5 Comments

paceaux Over a year ago

I tried that exact code and ended up with <img src="data:image/png;charset=utf-8;base64[object Object]" alt="Picture of item"> I think I need to somehow stringify that object in my computed prop

paceaux Over a year ago

Upon Closer review, it looks like the base64 apparently isn't valid. So that means there's a problem with how I'm submitting the image to the database

Frondor Over a year ago

You should be passing a Buffer to item.image before saving it. Add the code to the question so we can check if that's ok. Also, try setting long length to Sequelize.BLOB('long')

paceaux Over a year ago

I've updated the question to include how I'm adding the file. I also modified my model. How can I be sure that I'm passing a buffer? in my createImage method in my "add" template, it doesn't work even if I try this.item.template = file ... This is my ignorance as I'm not sure I know when a file becomes a buffer and vice versa

ContextCue Over a year ago

As a side note I tried these things: passed ArrayBuffer, converted with FileReader / passed base64 string (w and wo substr) / passed just the file from new FileReader() / passed the file from fs-web fileRead... a few of these options could be decoded with atob but the string was not valid after decoding.

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