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61 lines
2.3 KiB
HTML
61 lines
2.3 KiB
HTML
<!doctype html>
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<html>
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<head>
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<title>canvas.js | transformations</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<script type="text/javascript" src="../../pattern/canvas.js"></script>
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</head>
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<body>
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<script type="text/canvas">
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function setup(canvas) {
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canvas.size(500, 500);
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}
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function draw(canvas) {
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canvas.clear();
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// The simplest shapes to draw are rectangle, ellipse and line.
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// line() takes four parameters: x0, y0, x1, y1, the start and end coordinates.
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// rect() and ellipse() also take four parameters: x, y, width and height.
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// The default origin point (0,0) is the top-left corner of the canvas.
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// Draw a line from x=0 (horizontal) and y=0 (vertical) to x=100 and y=200.
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// stroke() sets the current outline color using R,G,B,A values between 0.0-1.0.
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stroke(0, 0, 0, 1);
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strokewidth(0.5);
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// From now on all shapes are drawn with a black stroke.
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line(0, 0, 100, 200);
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// Ellipses are positioned from their center:
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fill(1, 0, 0, 0.5); // red
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ellipse(0, 0, 100, 100);
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// Transformations translate(), rotate(), scale() use the current origin point.
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// This means that, by default, everything rotates around (0,0).
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// So a rectangle at (50,50) will rotate around the top-left corner of the canvas.
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// Rectangles are positioned from their top-left corner:
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push();
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rotate(canvas.frame); // canvas.frame increases by +1 each animation frame.
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fill(0, 1, 0, 0.5); // green
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rect(50, 50, 100, 100);
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pop();
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// translate() can be used to relocate the transformation origin point.
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// We place the origin point at (250,250).
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// All shapes and transformation will now originate from x=250 and y=250.
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// So a rectangle drawn at x=0 and y=0
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// will rotate with its top-left corner around this point.
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// We nudge it left and up so that rotates from its center:
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push();
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translate(250, 250);
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rotate(canvas.frame);
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fill(0, 0, 1, 0.5); // blue
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rect(-100, -100, 200, 200);
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pop();
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// Transformations between push() and pop() last until pop() is called.
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// The small purple rectangle follows the mouse:
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push();
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translate(canvas.mouse.x, canvas.mouse.y);
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rotate(canvas.frame*2);
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scale(1.0 + canvas.mouse.relative_x); // scale(1.0) = 100%
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fill(1, 0, 1, 0.5); // purple = blue + red
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rect(0, 0, 20, 20);
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pop();
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}
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</script>
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</body>
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</html> |