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How to Highlight Image Map Areas with Canvas Outlines?

Barbara Streisand
Release: 2024-12-12 22:56:14
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How to Highlight Image Map Areas with Canvas Outlines?

  1. Create a canvas element. This element will be used to draw the outlines of the areas when they are hovered over.
  2. Position the canvas element in front of the image map.
  3. Get the device context of the canvas. This context will be used to draw the outlines.
  4. Add event listeners to the areas. These event listeners will call functions to draw the outlines when the areas are hovered over.
  5. In the event listener functions, use the coords attribute of the area to get the coordinates of the shape.
  6. Use the getContext() method of the canvas to get the canvas's drawing context.
  7. Use the beginPath() method of the drawing context to start a new path.
  8. Use the moveTo() method of the drawing context to move the current point to the first coordinate of the shape.
  9. Use the lineTo() method of the drawing context to draw a line to each of the other coordinates of the shape.
  10. Use the closePath() method of the drawing context to close the path.
  11. Use the stroke() method of the drawing context to stroke the path, which will draw the outline of the shape.

Here is an example of how to implement this solution in JavaScript:

// Canvas element
var canvas = document.getElementById('myCanvas');
// Drawing context
var hdc = canvas.getContext('2d');

// Event listeners
for (var i = 0; i < areas.length; i++) {
  areas[i].addEventListener('mouseover', function() {
    var coords = this.getAttribute('coords');
    hdc.beginPath();
    hdc.moveTo(coords[0], coords[1]);
    for (var j = 2; j < coords.length; j += 2) {
      hdc.lineTo(coords[j], coords[j+1]);
    }
    hdc.lineTo(coords[0], coords[1]);
    hdc.stroke();
  });
  areas[i].addEventListener('mouseout', function() {
    hdc.clearRect(0, 0, canvas.width, canvas.height);
  });
}
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