How do you apply gradients to shapes on a canvas?
Aug 04, 2025 pm 12:39 PM
To apply a gradient to a Canvas shape, you need to follow the following steps: 1. Create a gradient using createLinearGradient() or createRadialGradient() and define its coordinate range; 2. Add one or more color nodes through addColorStop() to set the gradient color; 3. Assign the gradient object to the fillStyle or strokeStyle attribute; 4. Create a shape using fillRect, arc, etc. drawing methods, and the gradient will automatically fill. Note that the gradient is based on the canvas coordinate system. When moving the shape, the gradient coordinates need to be readjusted to maintain visual consistency. The final effect depends on the precise control of coordinate settings and color transitions.
Applying gradients to shapes on a canvas—especially in web development using HTML5 Canvas—requires a few clear steps. You create a gradient, assign it as the fill style, and then draw the shape. Here's how it works:
1. Create a Gradient with createLinearGradient() or createRadialGradient()
First, you need to define the type of gradient. The two main types are linear and radial.
- Linear Gradient : Flows in a straight line.
- Radial Gradient : Radiates outward from a central point.
const canvas = document.getElementById('myCanvas'); const ctx = canvas.getContext('2d'); // Create a linear gradient from left to right const linearGradient = ctx.createLinearGradient(0, 0, 200, 0); linearGradient.addColorStop(0, 'red'); linearGradient.addColorStop(1, 'blue'); // Or create a radial gradient const radialGradient = ctx.createRadialGradient(100, 100, 10, 100, 100, 50); radialGradient.addColorStop(0, 'yellow'); radialGradient.addColorStop(1, 'transparent');
The parameters for createLinearGradient(x1, y1, x2, y2) define the start and end points of the gradient line. For createRadialGradient(x1, y1, r1, x2, y2, r2) , you define two circles: where the gradient starts and ends.
2. Assign the Gradient as the Fill Style
Once the gradient is defined, set it as the current fillStyle :
ctx.fillStyle = linearGradient; // or ctx.fillStyle = radialGradient;
3. Draw the Shape
Now, when you draw a shape using methods like fillRect , fill , or arc , it will be filled with the gradient:
// Draw a rectangle with linear gradient ctx.fillRect(10, 10, 200, 100); // Draw a circle with radial gradient ctx.beginPath(); ctx.arc(100, 100, 50, 0, Math.PI * 2); ctx.fillStyle = radialGradient; ctx.fill();
Adding Multiple Color Stops
You can make gradients smoother or more complex by adding more color stops:
const gradient = ctx.createLinearGradient(0, 0, 200, 0); gradient.addColorStop(0, 'purple'); gradient.addColorStop(0.5, 'cyan'); gradient.addColorStop(1, 'orange'); ctx.fillStyle = gradient; ctx.fillRect(10, 130, 200, 100);
This creates a smooth transition across three colors.
A few things to keep in mind:
- Gradients are tied to canvas coordinates, not shape positions. So if you move a shape, the gradient won't automatically reposition unless you recreate it.
- You can also apply gradients to strokes using
strokeStyleinstead offillStyle.
Basically, it's about defining the gradient space, setting colors at key points, and using it like any other fill. Not hard once you get the coordinate logic down.
The above is the detailed content of How do you apply gradients to shapes on a canvas?. For more information, please follow other related articles on the PHP Chinese website!
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