Divide a picture with the help of javascript

Is there a way to utilize JavaScript to extract sections of an image and save them in an array, then showcase them randomly on an HTML5 canvas?

Answer №1

To achieve a clipped image effect, you can utilize the clip parameters within the drawImage() function and render the clipped image onto a dynamically generated canvas.

Here is an illustrative example:

function generateClippedCanvas(image, x, y, width, height) {
    var canvas = document.createElement('canvas'),
        ctx = canvas.getContext('2d');

    canvas.width = width;
    canvas.height = height;

    // Specify source region coordinates followed by destination region coordinates
    ctx.drawImage(image, x, y, width, height, 0, 0, width, height);

    return canvas;
}

This function will provide you with a canvas element containing the clipped image already rendered on it. Subsequently, you can directly apply this canvas to draw on another canvas.

For implementation, consider the following main code snippet:

var canvas = document.getElementById('myScreenCanvas'),
    ctx = canvas.getContext('2d'),
    image = document.getElementById('myImageId'),
    clip = generateClippedCanvas(image, 50, 20, 100, 100);

// Render the clipped image on the primary canvas
ctx.drawImage(clip, canvas.width * Math.random(), canvas.height * Math.random());

Answer №2

Alternatively, you could opt for the CSS sprite method, which is not only quicker but also simpler.

If you have an image (let's say my_Image.gif) and want to extract a specific portion using this technique, you can achieve it by setting the extract as a background of a DIV element. Check out the code snippet below.

portion1 in the parameters below instructs to "Extract a 100px high and 100px wide slice from my image, starting at the position 0px from the left (margin-left) and 0px from the top (margin-top)"

portion2 in the parameters below instructs to "Extract a 100px high and 100px wide slice from my image, starting at the position -91px from the left (margin-left) and 0px from the top (margin-top)"

By manipulating the pixels, you can extract portions of any size from any position. You can even use percentages as well.

Note: The image must be in gif format and located in the root directory of your server in this case...

You can also use other image formats like jpeg, png, etc.

 <!DOCTYPE html>
      <html>
        <head>
          <style>

            #portion1 {
                width: 100px;
                height: 100px;
                background: url(my_Image.gif) 0 0;
            }

            #portion2 {
                width: 100px;
                height: 100px;
                background: url(my_Image.gif) -91px 0;
            }
            </style>
            </head>
            <body>


             <div id="portion1"></div><br>
             <div id="portion2"></div>


              <script>
               //creating the array to hold the portions
               var ImagePortions = [
               "url('my_Image.gif') 0 0 ",
               "url('my_Image.gif') -91px 0"];

/*You can now create your canvas container that will act as the parent  of these array elements and use Math.random() to display the portions*/


       </script>

        </body>
        </html>

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