Snippets

Takumi IINO draw rest. add-subtract, translate-scale

Created by Takumi IINO last modified
index.html
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<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Draw Rect</title>
  </head>
  <body>
    <canvas id="canvas1" width="100" height="100"></canvas>
    <canvas id="canvas2" width="100" height="100"></canvas>
    <canvas id="canvas3" width="100" height="100"></canvas>
    <canvas id="canvas4" width="100" height="100"></canvas>
    <script>
      var onload = function() {
        draw1(document.getElementById('canvas1'));
        draw2(document.getElementById('canvas2'));
        draw3(document.getElementById('canvas3'));
        draw4(document.getElementById('canvas4'));
      };

      var draw1 = function(canvas) {
        var ctx = canvas.getContext('2d');
        var canvasWidth = canvas.getAttribute('width');
        var canvasHeight = canvas.getAttribute('height');

        var rectWidth = 20;
        var rectHeight = 20;

        var offsetX = 10;
        var offsetY = 10;

        ctx.beginPath();
        ctx.strokeRect(0, 0, canvasWidth, canvasHeight);

        [
          [offsetX,                           offsetY],
          [offsetX,                           canvasHeight - offsetY - rectHeight],
          [canvasWidth - offsetX - rectWidth, offsetY],
          [canvasWidth - offsetX - rectWidth, canvasHeight - offsetY - rectHeight]
        ].forEach(function(a) {
          var x = a[0];
          var y = a[1];
          ctx.beginPath();
          ctx.strokeRect(x, y, rectWidth, rectHeight);
        });
      };

      var draw2 = function(canvas) {
        var ctx = canvas.getContext('2d');
        var canvasWidth = canvas.getAttribute('width');
        var canvasHeight = canvas.getAttribute('height');

        var rectWidth = 20;
        var rectHeight = 20;

        var offsetX = 10;
        var offsetY = 10;

        ctx.beginPath();
        ctx.strokeRect(0, 0, canvasWidth, canvasHeight);

        [
          [0,           0,             1,  1], // 左上
          [canvasWidth, 0,            -1,  1], // 右上
          [0,           canvasHeight,  1, -1], // 左下
          [canvasWidth, canvasHeight, -1, -1]  // 右下
        ].forEach(function(a) {
          var translateX = a[0];
          var translateY = a[1];
          var scaleX = a[2];
          var scaleY = a[3];
          ctx.save();
          ctx.translate(translateX, translateY);
          ctx.scale(scaleX, scaleY);
          ctx.strokeRect(offsetX, offsetY, rectWidth, rectHeight);
          ctx.restore();
        });
      };

      var draw3 = function(canvas) {
        var ctx = canvas.getContext('2d');
        var canvasWidth = canvas.getAttribute('width');
        var canvasHeight = canvas.getAttribute('height');

        var rectWidth = 20;
        var rectHeight = 20;

        var offsetX = 10;
        var offsetY = 10;

        ctx.beginPath();
        ctx.strokeRect(0, 0, canvasWidth, canvasHeight);

        [
          [0,           0,             1,  1], // 左上
          [canvasWidth, 0,            -1,  1], // 右上
          [0,           canvasHeight,  1, -1], // 左下
          [canvasWidth, canvasHeight, -1, -1]  // 右下
        ].forEach(function(a) {
          var translateX = a[0];
          var translateY = a[1];
          var scaleX = a[2];
          var scaleY = a[3];
          ctx.save();
          ctx.translate(translateX, translateY);
          ctx.scale(scaleX, scaleY);
          myRect1(ctx, offsetX, offsetY, rectWidth, rectHeight);
          ctx.restore();
        });
      };

      var draw4 = function(canvas) {
        var ctx = canvas.getContext('2d');
        var canvasWidth = canvas.getAttribute('width');
        var canvasHeight = canvas.getAttribute('height');

        var rectWidth = 20;
        var rectHeight = 20;

        var offsetX = 10;
        var offsetY = 10;

        ctx.beginPath();
        ctx.strokeRect(0, 0, canvasWidth, canvasHeight);

        [
          [0,           0,             1,  1], // 左上
          [canvasWidth, 0,            -1,  1], // 右上
          [0,           canvasHeight,  1, -1], // 左下
          [canvasWidth, canvasHeight, -1, -1]  // 右下
        ].forEach(function(a) {
          var translateX = a[0];
          var translateY = a[1];
          var scaleX = a[2];
          var scaleY = a[3];
          ctx.save();
          ctx.translate(translateX, translateY);
          ctx.scale(scaleX, scaleY);
          myRect2(ctx, offsetX, offsetY, rectWidth, rectHeight);
          ctx.restore();
        });
      };


      function myRect1(ctx, x, y, width, height) {
        ctx.beginPath();
        ctx.moveTo(x, y);
        ctx.lineTo(x + width, y);
        ctx.lineTo(x + width, y + height);
        ctx.lineTo(x, y + height);
        ctx.lineTo(x, y);
        ctx.stroke();
      }

      function myRect2(ctx, x, y, width, height) {
        ctx.save();
        ctx.translate(x, y);
        ctx.beginPath();
        ctx.moveTo(0, 0);
        ctx.lineTo(width, 0);
        ctx.lineTo(width, height);
        ctx.lineTo(0, height);
        ctx.lineTo(0, 0);
        ctx.stroke();
        ctx.restore();
      }

      window.addEventListener('load', onload, false);
    </script>
  </body>
</html>

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