In Javascript, swap out a particular colored region in an image with a different image

Question

In Javascript, swap out a particular colored region in an image with a different image

I've been scouring the internet in search of a solution to my problem, but it seems like I might not be looking in the right places.

Imagine this image below, how can I replace the blue area with an image uploaded by the user? I'm struggling to figure out how to achieve this.

I stumbled upon this which talks about drawing a red rectangle based on specific coordinates, but what I need (I believe) is to identify those coordinates and swap them out with an image. Has anyone encountered this before? Any guidance would be greatly appreciated as I'm stuck here!

https://i.sstatic.net/rrGp5.jpg

Please note that the image used here is just for illustrative purposes and does not belong to me. Thank you for your help.

EDIT:

I realize I should have included the code initially, apologies for that oversight. This project is built using phonegap and jquery mobile, with a navbar at the bottom. One of the pages, named "preview," requires the functionality to change images, but I seem to be missing something due to lack of knowledge:

My index.html:

 <div data-role="page" data-url="preview" id="preview">
      <div data-role="header" style="background-color: rgb(182, 202, 51)" data-position="fixed">
        <h1 id="titlePreview">PREVIEW</h1>
        <a href="#language" id="langBtn" style="width: 20px;height: 20px; background:none;  " href="#" data-icon="comment" data-iconpos="notext" class="ui-btn-left"></a>
      </div>
        <div id="previewSaco" class="containerPreviewSaco">//if i remove this div, the navbar on the bottom disapears. 
          <canvas id="myCanvas" width="200" height="200">//i´m testing with this size, but yes the image is supose to have a 100% with, in fact the image as 1940x2372. 
       </div>
      <div data-role="footer" data-position="fixed">
        <div data-role="navbar" class="ui-bar">
          <ul>
            //in here i have my several "li" for navegation and i think it´s irrelevant for my question.
          </ul>
        </div>
      </div>
    </div>

My .js file:

$(document).on("click", "#btnPreview", function (event) {

    var ctx = document.getElementById('myCanvas').getContext('2d');

    var img = new Image;
    img.onload = function(){
      ctx.drawImage(img,0,0);
      img2.src = 'img/capa.png'; 
    };

    var img2 = new Image;
    img2.onload = function(){
        ctx.globalCompositeOperation = 'destination-over';

      //ctx.scale(x, y);
      //ctx.rotate(angle);
      //ctx.translate(x, y);

      //or

      //ctx.transform(a, b, c, d, e, f);

      ctx.drawImage(img2,0,0);
    };

    var uri1 = 'img/previewSaco1.png'; //the main image supposed to load on page click "preview", **but it's not happening** also featuring a transparent area for user-uploaded images.

    var uri2 = 'img/capa.png';//a dummy logo image for larger image testing
    img.src = uri1;
});

Note: when running the app, the phonegap desktop constantly displays: undefined Content Security Policy has been modified to be: https://ssl.gstatic.com;style-src 'self' 'unsafe-inline' data: blob:;media-src *;img-src * 'self' data: content:;script-src * 'unsafe-inline' 'unsafe-eval' data: blob:;">

javascript html css html5-canvas

Answer 1

Answer №1

Alright, let's dive in:

Utilize the following HTML structure:

<div id="imageContainer" class="center">
<h2>Let's explore and see where it leads</h2>
<img class="pic" src="https://moltopiccolo.files.wordpress.com/2012/01/cool-drinks.jpg"> 
</div>

You have the flexibility to set any background image on the container div without affecting the layout.

The image employs CSS clip path which requires multiple prefixes for compatibility, but the visual results are stunning. You can shape your image using clip path generators available online and even animate it.

Here is an example of mine:

#imageContainer img {
-webkit-clip-path: polygon(1% 3%, 3% 9%, 18% 21%, 54% 20%, 83% 63%, 66% 76%, 
15% 83%, 25% 45%);
clip-path: polygon(17% 13%, 33% 9%, 58% 21%, 84% 20%, 83% 63%, 66% 76%, 15% 
83%, 25% 45%);
-webkit-transition: -webkit-clip-path .6s ease-out;
transition: -webkit-clip-path .6s ease-out;
position:absolute;
border-radius: 5px;
width: 100%;
height:270px;

}

I've also added an input button for file upload, along with the following JavaScript function:

var getval = document.querySelector("#getval");

getval.addEventListener("change", previewFile);

function previewFile() {
var reader = new FileReader();
var bgImage = document.querySelector(".pic");
var file = document.querySelector("input[type=file]").files[0];
reader.onloadend = function() {
bgImage.src = reader.result;
};

if (file) {
reader.readAsDataURL(file); //reads the data as a URL
 } else {
file.src = "";
}
}

For a demonstration, visit this link:

https://codepen.io/damianocel/pen/KdobyK

Answer 2

Alright, let's dive in:

Utilize the following HTML structure:

<div id="imageContainer" class="center">
<h2>Let's explore and see where it leads</h2>
<img class="pic" src="https://moltopiccolo.files.wordpress.com/2012/01/cool-drinks.jpg"> 
</div>

You have the flexibility to set any background image on the container div without affecting the layout.

The image employs CSS clip path which requires multiple prefixes for compatibility, but the visual results are stunning. You can shape your image using clip path generators available online and even animate it.

Here is an example of mine:

#imageContainer img {
-webkit-clip-path: polygon(1% 3%, 3% 9%, 18% 21%, 54% 20%, 83% 63%, 66% 76%, 
15% 83%, 25% 45%);
clip-path: polygon(17% 13%, 33% 9%, 58% 21%, 84% 20%, 83% 63%, 66% 76%, 15% 
83%, 25% 45%);
-webkit-transition: -webkit-clip-path .6s ease-out;
transition: -webkit-clip-path .6s ease-out;
position:absolute;
border-radius: 5px;
width: 100%;
height:270px;

}

I've also added an input button for file upload, along with the following JavaScript function:

var getval = document.querySelector("#getval");

getval.addEventListener("change", previewFile);

function previewFile() {
var reader = new FileReader();
var bgImage = document.querySelector(".pic");
var file = document.querySelector("input[type=file]").files[0];
reader.onloadend = function() {
bgImage.src = reader.result;
};

if (file) {
reader.readAsDataURL(file); //reads the data as a URL
 } else {
file.src = "";
}
}

For a demonstration, visit this link:

https://codepen.io/damianocel/pen/KdobyK

Answer 3

Answer №2

To achieve a layered effect in your canvas drawing, consider using the

Context2D.globalCompositeOperation = 'destination-over';

. For more detailed information, visit GlobalCompositeOperation documentation.

Start by editing your image in an editor and removing the section you wish to replace by making those pixels transparent. Then, load this modified image onto the canvas.

Next, load the new image you want to insert. Use

ctx.globalCompositeOperation = 'destination-over';

to superimpose this image on top of the existing one in the canvas.

If needed, apply a transformation to the canvas before adding the second image for better alignment.

Refer to this example on jsfiddle: jsfiddle.net

Edit 1: Instead of manually setting transparency, consider adjusting it based on color after loading the initial image. This answer on stackoverflow might help: this answer.

Answer 4

To achieve a layered effect in your canvas drawing, consider using the

Context2D.globalCompositeOperation = 'destination-over';

. For more detailed information, visit GlobalCompositeOperation documentation.

Start by editing your image in an editor and removing the section you wish to replace by making those pixels transparent. Then, load this modified image onto the canvas.

Next, load the new image you want to insert. Use

ctx.globalCompositeOperation = 'destination-over';

to superimpose this image on top of the existing one in the canvas.

If needed, apply a transformation to the canvas before adding the second image for better alignment.

Refer to this example on jsfiddle: jsfiddle.net

Edit 1: Instead of manually setting transparency, consider adjusting it based on color after loading the initial image. This answer on stackoverflow might help: this answer.

In Javascript, swap out a particular colored region in an image with a different image

Answer №1

Answer №2

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