CanvasRenderingContext2D: shadowBlur property

{{APIRef("Canvas API")}}

The CanvasRenderingContext2D.shadowBlur property of the Canvas 2D API specifies the amount of blur applied to shadows. The default is 0 (no blur).

[!NOTE] Shadows are only drawn if the {{domxref("CanvasRenderingContext2D.shadowColor", "shadowColor")}} property is set to a non-transparent value. One of the shadowBlur, {{domxref("CanvasRenderingContext2D.shadowOffsetX", "shadowOffsetX")}}, or {{domxref("CanvasRenderingContext2D.shadowOffsetY", "shadowOffsetY")}} properties must be non-zero, as well.

Value

A non-negative float specifying the level of shadow blur, where 0 represents no blur and larger numbers represent increasingly more blur. This value doesn't correspond to a number of pixels, and is not affected by the current transformation matrix. The default value is 0. Negative, {{jsxref("Infinity")}}, and {{jsxref("NaN")}} values are ignored.

Examples

Adding a shadow to a shape

This example adds a blurred shadow to a rectangle. The shadowColor property sets its color, and shadowBlur sets its level of blurriness.

HTML

<canvas id="canvas"></canvas>

JavaScript

const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

// Shadow
ctx.shadowColor = "red";
ctx.shadowBlur = 15;

// Rectangle
ctx.fillStyle = "blue";
ctx.fillRect(20, 20, 150, 100);

Result

{{ EmbedLiveSample('Adding_a_shadow_to_a_shape', 700, 180) }}

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

WebKit/Blink-specific notes

In WebKit- and Blink-based browsers, the non-standard and deprecated method ctx.setShadow() is implemented besides this property.

setShadow(width, height, blur, color, alpha);
setShadow(width, height, blur, graylevel, alpha);
setShadow(width, height, blur, r, g, b, a);
setShadow(width, height, blur, c, m, y, k, a);

See also

• The interface defining this property: {{domxref("CanvasRenderingContext2D")}}
• {{domxref("CanvasRenderingContext2D.shadowColor")}}