我們可以透過建立fabric.Polygon的實例來建立一個Polygon物件。多邊形物件的特徵可以是由一組連接的直線段組成的任何閉合形狀。由於它是 FabricJS 的基本元素之一,我們也可以透過應用角度、不透明度等屬性輕鬆自訂它。為了找到表示目前變換的變換矩陣,我們使用 calcOwnMatrix 方法。
calcOwnMatrix(): Array
讓我們來看一個程式碼範例,了解如何使用 calcOwnMatrix 方法找到表示多邊形目前變換的變換矩陣。您可以從開發工具開啟控制台來查看正在顯示的陣列值。
<!DOCTYPE html> <html> <head> <!-- Adding the Fabric JS Library--> <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script> </head> <body> <h2>Using the calcOwnMatrix method</h2> <p> You can open console from dev tools and see that the logged output contains the transform matrix of the polygon instance </p> <canvas id="canvas"></canvas> <script> // Initiate a canvas instance var canvas = new fabric.Canvas("canvas"); canvas.setWidth(document.body.scrollWidth); canvas.setHeight(250); // Initiating a polygon object var polygon = new fabric.Polygon( [ { x: 200, y: 10 }, { x: 250, y: 50 }, { x: 250, y: 180 }, { x: 150, y: 180 }, { x: 150, y: 50 }, { x: 200, y: 10 }, ], { fill: "green", stroke: "blue", strokeWidth: 20, skewX: 15, } ); // Adding it to the canvas canvas.add(polygon); // Using calcOwnMatrix method console.log( "The transform matrix which represents current transformation of the polygon instance is: ", polygon.calcOwnMatrix() ); </script> </body> </html>
讓我們看一個程式碼範例,以了解當我們對多邊形物件應用水平縮放時,傳回數組的值是如何受到影響的。在這裡,我們向scaleX屬性傳遞了值2。這確保了我們的多邊形物件在水平方向上縮放2倍。我們也可以在控制台中看到傳回數組的第0個索引值發生了變化。這是因為第 0 個索引表示scaleX 值。
<!DOCTYPE html> <html> <head> <!-- Adding the Fabric JS Library--> <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script> </head> <body> <h2>Using the calcOwnMatrix method along with scaleX property</h2> <p> You can open console from dev tools and see that the logged output has changed </p> <canvas id="canvas"></canvas> <script> // Initiate a canvas instance var canvas = new fabric.Canvas("canvas"); canvas.setWidth(document.body.scrollWidth); canvas.setHeight(250); // Initiating a polygon object var polygon = new fabric.Polygon( [ { x: 200, y: 10 }, { x: 250, y: 50 }, { x: 250, y: 180 }, { x: 150, y: 180 }, { x: 150, y: 50 }, { x: 200, y: 10 }, ], { fill: "green", stroke: "blue", strokeWidth: 20, skewX: 15, scaleX: 2, } ); // Adding it to the canvas canvas.add(polygon); // Using calcOwnMatrix method console.log( "The transform matrix which represents current transformation of the polygon instance is: ", polygon.calcOwnMatrix() ); </script> </body> </html>
在本教學中,我們使用兩個簡單的範例來示範如何使用 FabricJS 找到表示 Polygon 物件目前變換的變換矩陣。
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