How to achieve pressure-aware painting effects in HTML5 Canvas?

Simulate real brushstrokes: HTML5 Canvas pressure-perceptual painting

Many applications, such as bank electronic signature function, require changing the thickness of the line according to the user's brushstroke. This article will explain how to achieve this pressure-sensitive painting effect in HTML5 Canvas, simulating a real writing experience.

The user hopes that in the electronic signature, press hard to generate thick lines and lightly press thin lines. How to implement it in Canvas?

The key is to utilize the properties of the TouchEvent. The TouchEvent object contains rich touch information, including attributes that reflect pressure or contact area. Although no specific link is provided in the article, the core idea is to dynamically adjust the brush thickness using attributes in TouchEvent that are related to pressure or contact area (specific attributes may vary from browser to browser).

For example, calculate the brush thickness based on the TouchEvent property value (assuming that the greater the value, the greater the pressure):

 // Simplify the example, the actual code needs to be adapted to the browser and device let ctx = canvas.getContext('2d');
canvas.addEventListener('touchmove', (e) => {
  let touch = e.touches[0];
  let pressure = touch.force || touch.radiusX || 1; // Get the pressure value, if it does not exist, it defaults to 1
  let lineWidth = 2 pressure * 5; // Adjust linewidth according to pressure ctx.lineWidth = lineWidth;
  // ... Draw code...
});

This code snippet demonstrates how to calculate line width based on assumed pressure properties. In actual development, you need to consult the documents to determine the available pressure or contact area attributes and adjust the formula according to actual conditions. TouchEvent support may vary slightly from browser and device to device, and sufficient testing and compatibility are required. The final effect depends on the attributes and formula adjustments used.

The above is the detailed content of How to achieve pressure-aware painting effects in HTML5 Canvas?. For more information, please follow other related articles on the PHP Chinese website!