From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:40:17 -0500 Subject: initial commit --- .../api/canvasrenderingcontext2d/scale/index.html | 133 +++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 files/zh-cn/web/api/canvasrenderingcontext2d/scale/index.html (limited to 'files/zh-cn/web/api/canvasrenderingcontext2d/scale/index.html') diff --git a/files/zh-cn/web/api/canvasrenderingcontext2d/scale/index.html b/files/zh-cn/web/api/canvasrenderingcontext2d/scale/index.html new file mode 100644 index 0000000000..db95fca214 --- /dev/null +++ b/files/zh-cn/web/api/canvasrenderingcontext2d/scale/index.html @@ -0,0 +1,133 @@ +--- +title: CanvasRenderingContext2D.scale() +slug: Web/API/CanvasRenderingContext2D/scale +translation_of: Web/API/CanvasRenderingContext2D/scale +--- +
{{APIRef}}
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CanvasRenderingContext2D.scale() 是 Canvas 2D API 根据 x 水平方向和 y 垂直方向，为canvas 单位添加缩放变换的方法。

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默认的， 在 canvas 中一个单位实际上就是一个像素。例如，如果我们将0.5作为缩放因子，最终的单位会变成0.5像素，并且形状的尺寸会变成原来的一半。相似的方式，我们将2.0作为缩放因子，将会增大单位尺寸变成两个像素。形状的尺寸将会变成原来的两倍。

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语法

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void ctx.scale(x, y);
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参数

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x
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水平方向的缩放因子。A negative value flips pixels across the vertical axis. A value of 1 results in no horizontal scaling.
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y
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垂直方向的缩放因子。A negative value flips pixels across the horizontal axis. A value of 1 results in no vertical scaling.
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示例

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使用 scale 方法

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这是一段使用 scale 方法的简单的代码片段。

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HTML

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

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The rectangle has a specified width of 8 and a height of 20. The transformation matrix scales it by 9x horizontally and by 3x vertically. Thus, its final size is a width of 72 and a height of 60.

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Notice that its position on the canvas also changes. Since its specified corner is (10, 10), its rendered corner becomes (90, 30).

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const canvas = document.getElementById('canvas');
+const ctx = canvas.getContext('2d');
+
+// Scaled rectangle
+ctx.scale(9, 3);
+ctx.fillStyle = 'red';
+ctx.fillRect(10, 10, 8, 20);
+
+// Reset current transformation matrix to the identity matrix
+ctx.setTransform(1, 0, 0, 1, 0, 0);
+
+// Non-scaled rectangle
+ctx.fillStyle = 'gray';
+ctx.fillRect(10, 10, 8, 20);
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结果

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The scaled rectangle is red, and the non-scaled rectangle is gray.

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

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使用 scale 水平或竖直翻转

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你可以使用 ctx.scale(-1, 1) 水平翻转上下文，使用 ctx.scale(1, -1) 垂直翻转上下文。在这个例子中，"Hello world!" 被水平翻转。

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Note that the call to {{domxref("CanvasRenderingContext2D.fillText()", "fillText()")}} specifies a negative x coordinate. This is to adjust for the negative scaling factor: -280 * -1 becomes 280, and text is drawn leftwards from that point.

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HTML

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

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const canvas = document.getElementById('canvas');
+const ctx = canvas.getContext('2d');
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+ctx.scale(-1, 1);
+ctx.font = '48px serif';
+ctx.fillText('Hello world!', -280, 90);
+ctx.setTransform(1, 0, 0, 1, 0, 0);
+
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Result

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

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规范描述

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SpecificationStatusComment
{{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-scale", "CanvasRenderingContext2D.scale")}}{{Spec2('HTML WHATWG')}}
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浏览器兼容性

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{{Compat("api.CanvasRenderingContext2D.scale")}}

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参见

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