Image Manipulation with Fabric.js and Canvas

• fabric.js

  49 27,419 9.3 JavaScript

  Javascript Canvas Library, SVG-to-Canvas (& canvas-to-SVG) Parser

  

body{ display:flex; flex-direction:column; align-items:center; }

Learning Fabric

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Next, we initiate a Canvas instance in our script tag:

Syntax


new fabric.Canvas(element: HTMLElement|String, options: Object)

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This allows Fabric.js to create this class instance so that we can use the provided methods of Fabric.js:


const canvas = new fabric.Canvas("canvas", {})

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Now, we’ll go ahead and give our canvas different properties, such as width, height, and background color:


const canvas = new fabric.Canvas("canvas", {
 width:500,
 height:500,
 backgroundColor:green
})

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Output



Creating a Rectangle with Fabric.js

Now that we’ve initialized a canvas and given it various properties, we’re going to create a rectangle using the Fabric.js object fabric.Rect:

Syntax


new fabric.Rect({object})

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Here the object houses the rectangle properties:


const canvas = new fabric.Canvas("canvas", {
 width:500,
 height:500,
 backgroundColor:green
});

const rectangle = new fabric.Rect({
 width:200,
 height:200,
 /* fill is used to define the background color*/
    fill:'red'
})
/*the add method is used to add objects to the canvas element */
canvas.add(rectangle)
/*the renderAll method used to render the canvas*/
canvas.renderAll();

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The add() method is used to add objects to the Canvas element. In this case, it adds the rectangle we created to the canvas:

Output



Creating a Circle

In the same way, we’ll create a circle. This time, we’ll use fabric.Circle:


const canvas = new fabric.Canvas("canvas", {
 width:500,
 height:500,
 backgroundColor:"lightgray"
});

const circle = new fabric.Circle({
 radius:60,
 fill:"blue"
})
canvas.add(circle);
canvas.renderALl();

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Output



With the above steps, we created a rectangle and a circle using Fabric.js. Note how interactive the objects are! Next, we’ll discuss images in Fabric.js.

Images with Fabric

The Fabric.Image is a Fabric.js object used to render images on a canvas. With Fabric.js, we can interact with the image. Images can be added to our canvas in two ways:

• Fabric.Image
• Fabric.Image.fromURL

Using the Fabric.Image constructor requires us to create an image element in our HTML and then insert it into the constructor:

Syntax


fabric.Image(image_element)

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HTML


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JS


const image_element = document.querySelector('#image');
const image = new fabric.Image(image_element)
canvas.add(image);
canvas.renderAll();

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However, Fabric.Image.fromURL requires only the image URL (the URL can be retrieved from a website or your local folder), and is simpler than the former:


fabric.Image.fromURL(URL, function());

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After passing the URL, the callback function after the image is loaded. The first default parameter of the callback function is the fabric.Image object. Now, we can modify the image properties and then add it to the canvas:


const canvas = new fabric.Canvas("canvas", {
 width:500,
 height:500,
 backgroundColor:"White"
});

fabric.Image.fromURL('my_image.png',(img) => {
 // the scaleToHeight property is use to set the image height
    img.scaleToHeight(250)
 // scaleToWidth is use to set the image width
    img.scaleToWidth(250)
    canvas.add(img)  
})
canvas.renderAll()

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Output



Editing Images with Fabric.js

Now that we know how to insert an image into a canvas, we’ll look at other image objects like image filters.

Image Filters

Fabric.js provides us with built-in filters:

• BaseFilter
• Brightness
• convolute
• GradientTransparency
• Grayscale
• Invert
• Mask
• Noise
• Pixelate
• RemoveWhite
• Sepia
• Sepia2
• Tint

Every instance of fabric.Image has the "filters" property, which is a simple array of filters. We can use the array method to perform any required operation, including removing filters (pop, slice, shift), adding filters (push, unshift, slice), and even combining multiple filters. When we call applyFilters, any filter in the “filters” array will be applied one by one. Let’s use some of these filters:

Syntax


new fabric.Image.filters
// after that you can add any filter of your choice
// Example 
new fabric.Image.filters.Grayscale()

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fabric.Image.fromURL('my_image.png', (image) => {
      image.scaleToHeight(300)
       image.ScaleToWidth(300)

 // Creating filter
 const filter = new fabric.Image.filters.Grayscale()

 //push the filter instance to filters
        image.filter.push(filter)

 // apply filter
         image.applyFilters()

 //add image into canvas (it also re-render the canvas)
         canvas.add(image)
},{crossOrigin: 'anonymous'});
canvas.renderAll();

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Output



Above, we used the Grayscale filter; we can also apply other filters. All we have to do is simply change the filter, as shown in this example:


fabric.Image.fromURL('my_image.png', (image) => {
      image.scaleToHeight(300)
       image.ScaleToWidth(300)

 // creating filter
 const filter = new fabric.Image.filters.Sepia()

 //add filter
        image.filter.push(filter)

 // apply filter
         image.applyFilters()

 //add image into canvas (it also re-render the canvas)
         canvas.add(image)
},{crossOrigin: 'anonymous'});
canvas.renderAll();

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Output



Image Blending

Blending is mixing two or more images to create a new image. Fabric.js gives us this ability. Here, we’re going to use the image blending filter for our image:

Syntax


new fabric.Image.filters.BlendImage({
 // the image that we want to blend
          image:imageA,
 // blend mode (in this case we are using the 'add' mode)
          mode:'add',

 alpha:0.5
      });

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fabric.Image.fromURL('my_image.png', (imageA) => {
    imageA.scaleToWidth(350)
    imageA.scaleToHeight(350)
    canvas.add(imageA)

 // Blending filter
    filter = new fabric.Image.filters.BlendImage({
 image:imageA,
 mode:'add',
 alpha:0.5
      });

 //Add the second image  
     fabric.Image.fromURL('my_image2.png',(imageB) => {
           imageB.scaleToHeight(100),
            imageB.scaleToWidth(100),
            canvas.add(imageB)
       }, {crossOrigin:''});

     imageA.filters.push(filter);
     imageA.applyFilters(canvas.renderAll.bind(canvas));
},{crossOrigin:''})

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Output



Image Clipping

A very popular effect used today is image clipping, or rather image cropping, which is done to remove parts of an image that we don’t want. With Fabric.js, we can achieve this by using the clipPath method.

First, we have to create our own clipPath using any Fabric.js object. Then, we’ll assign it to the clipPath property of the object we want to clip. Here, we’ll use a circle object:


const clipPath = new fabric.Circle({
 radius:150,
 top:200,
 left:250,
 // The originY and originX helps to center the image and the clipPath
    originY:"center",
 originX:"center"
})

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After that, we add it to the image that we want to clip using the filter method:


new fabric.Image.fromURL('my_image.png',(img) => {
  img.scaleToHeight(300)
  img.scaleToWidth(300)
 // positioning the image
  img.scale(o.5).set({top:50,left:100})
 // Clip Path
  clipPath = new fabric.Circle({
 radius:150,
 top:200,
 left:250,
 originY:"center",
 originX:"center"
    })
  canvas.add(img)
  canvas.clipPath = clipPath;
  });
canvas.renderAll();

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Output



Image Blurring

Like other image filters, the blur filter accepts objects because they can be adjusted. A practical example is changing the brightness of an image. You can apply other image filters without any additional configurations (like grayscale, invert, or sepia). Other image filters like brightness, pixelate, tint, and noise all operate in this way, too. However, the difference is that their values are not the same. The brightness filter's actual brightness level ranges from-1 (full black) to 1 (full white). The noise filter's value is between 0 and 1000. For the blur filter, the value ranges from 0 to 10.

Syntax


new fabric.Image.filters.Blur(object)

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fabric.Image.fromURL('my_image.png', (image) => {
      image.scaleToHeight(300)
       image.ScaleToWidth(300)

 // Creating the blur filter
 const filter = new fabric.Image.filters.Blur({
 blur:0.6
       })

 //push the filter instance to filters
        image.filter.push(filter)
         image.applyFilters()
         canvas.add(image)
},{crossOrigin: 'anonymous'});
canvas.renderAll();

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Output



Conclusion

In conclusion, Fabric.js gives us an awesome experience when working with Canvas. It also provides a lot of features, some of which we covered in this article. For full details on some of the Fabric.js objects, you can review its documentation here.

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