Fill a shape with a pattern (to create shutter effect) - bartbutenaers/node-red-contrib-ui-svg GitHub Wiki

SVG offers patterns, which are shapes that will be repeated in X and y directions. Such patterns can be used to fill the area of other shapes.

Draw a roller shutter

We will show the steps to display a roller shutter for a house:

  1. A typical roller shuttor consists out of long narrow rectangles, which are repeated a number of times:

    image

  2. One way to simulate such an effect, is by creating a pattern that consists out of a lightgrey rectangle followed by a black line:

    <defs>
   <pattern id="shutter_pattern" width="6" height="6" patternUnits="userSpaceOnUse">
      <rect x="0" y="0" width="6" height="6" fill="lightgrey" stroke="none"/>
      <line x1="0" y1="2" x2="6" y2="2" stroke="black" stroke-width="2"/>
   </pattern>
</defs>

    This pattern has very small dimensions (i.e. 6 x 6), but can be repeated by the browser in both X and Y directions.

  3. We can now draw a rectangle that represents the window itself:

    <rect id="imagebackground" x="0" y="0" width="50" height="80" stroke="none" fill="url(#shutter_pattern)"/>

    The pattern is applied to the window rectangle, by specifying the pattern id via a fill url.

  4. The browser will repeat the pattern in both directions to fill the entire window rectangle, resulting in a closed roller shutter:

    image

Open/close the roller shutter

As shown above, the browser will fill the entire window rectangle. However most of the time the roller shutter will be open completely or partially. I didn't find a simple way to achieve this, so we will solve this by using two separate rectangles:

  1. Use the same pattern as in the above example.

  2. Create two separate rectangles:

    <rect x="0" y="0" width="50" height="80" stroke="none" fill="white"/>
<rect x="0" y="0" width="50" height="40" stroke="none" fill="url(#shutter_pattern)" id="roller_shutter"/>

    We draw a large white rectangle that represents the entire window. On top of that we draw a rectangle of half the height, which gets the roller shutter pattern.

  3. This will result in the roller shutter being half open:

    image

  4. Since the roller shutter rectangle has an id (i.e. "roller_shutter"), we can inject a message to change the rectangle height:

    payload = {
 command: "set_attribute",
 selector: "#roller_shutter",
 attributeName: "height",
 attributeValue: msg.payload
}

The following example flow shows how this works:

image

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Which works like this:

pattern_fill_demo

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