canvas_drawing_example_20150724.html
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<!DOCTYPE html>
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<html lang="en"> |
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<head>
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<meta charset="utf-8" /> |
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<title>Canvas Drawing Example</title> |
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<script>
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var canvas;
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var ctx;
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var pixel;
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var pixData;
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function drawPixel(ctx, x, y, color)
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{
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pixData[0] = color[0];
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pixData[1] = color[1];
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pixData[2] = color[2];
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ctx.putImageData(pixel, x, y);
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}
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function rawLine(ctx, x1, y1, x2, y2, color)
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{
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var dx = Math.abs(x2 - x1);
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var dy = Math.abs(y2 - y1);
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var xIncr = dx > 0 ? 1 : -1;
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var yIncr = dy > 0 ? 1 : -1;
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dy = dy * -1;
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var err = dx + dy;
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var err2;
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var x = x1;
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var y = y1;
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while (true)
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{
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drawPixel(ctx, x, y, color);
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if (x == x2 && y == y2)
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break;
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err2 = err * 2;
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if (err2 >= dy)
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{
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err += dy;
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x += xIncr;
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}
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if (err2 <= dx)
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{
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err += dx;
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y += yIncr;
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}
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}
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}
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function drawLine(x1, y1, x2, y2)
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{
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ctx.beginPath();
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ctx.moveTo(x1, y1);
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ctx.lineTo(x2, y2);
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ctx.stroke();
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}
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function renderClosedPath(ctx, fill)
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{
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ctx.save();
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ctx.clip();
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if (fill)
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{
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ctx.fill();
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}
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else
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{
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ctx.stroke();
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}
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ctx.restore();
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}
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//
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// Draw a rounded rectangle with the given context, dimensions and fill.
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//
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// @param {CanvasRenderingContext2D} ctx
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// The canvas 2D graphics context.
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// @param {Number} x
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// X coordinate of the top left of the rectangle (if a square corner was placed
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// there).
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// @param {Number} y
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// Y coordinate of the top left of the rectangle (if a square corner was placed
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// there).
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// @param {Number} width
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// Width of the rectangle.
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// @param {Number} height
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// Height of the rectangle.
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// @param {Number} diameter
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// Diameter of the arc that defines the rounded corner.
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// @param {Boolean} fill
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// <code>true</code> to fill the rectangle with the current color, otherwise just
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// stroke the rectangle.
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//
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function createRoundRect(ctx, x, y, width, height, diameter, color, fill)
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{
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var radius = diameter / 2;
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// arc control points
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var northWestX = x;
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var northWestY = y;
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var northEastX = x + width;
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var northEastY = y;
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var southWestX = x;
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var southWestY = y + height;
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var southEastX = x + width;
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var southEastY = y + height;
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// line end points
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var topLeftX = northWestX + radius;
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var topLeftY = northWestY;
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var topRightX = northEastX - radius;
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var topRightY = northEastY;
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var rightUpX = northEastX;
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var rightUpY = northEastY + radius;
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var rightDownX = southEastX;
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var rightDownY = southEastY - radius;
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var bottomRightX = southEastX - radius;
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var bottomRightY = southEastY;
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var bottomLeftX = southWestX + radius;
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var bottomLeftY = southWestY;
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var leftDownX = southWestX;
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var leftDownY = southWestY - radius;
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var leftUpX = northWestX;
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var leftUpY = northWestY + radius;
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ctx.beginPath();
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ctx.moveTo(topRightX, topRightY);
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ctx.quadraticCurveTo(northEastX, northEastY, rightUpX, rightUpY);
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ctx.lineTo(rightDownX, rightDownY);
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ctx.quadraticCurveTo(southEastX, southEastY, bottomRightX, bottomRightY);
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ctx.lineTo(bottomLeftX, bottomLeftY);
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ctx.quadraticCurveTo(southWestX, southWestY, leftDownX, leftDownY);
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ctx.lineTo(leftUpX, leftUpY);
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ctx.quadraticCurveTo(northWestX, northWestY, topLeftX, topLeftY);
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ctx.closePath();
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renderClosedPath(ctx, fill);
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// overdraw the anti-aliased line segments
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rawLine(ctx, topLeftX, topLeftY, topRightX, topRightY, color);
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rawLine(ctx, rightUpX, rightUpY, rightDownX, rightDownY, color);
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rawLine(ctx, bottomLeftX, bottomLeftY, bottomRightX, bottomRightY, color);
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rawLine(ctx, leftUpX, leftUpY, leftDownX, leftDownY, color);
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}
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function parseColor(spec)
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{
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if (typeof spec !== "string")
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{
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return null;
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}
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if (spec.length !== 7)
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{
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return null;
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}
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if (spec.charAt(0) !== "#")
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{
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return null;
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}
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var r = parseInt(spec.substr(1, 2), 16);
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var g = parseInt(spec.substr(3, 2), 16);
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var b = parseInt(spec.substr(5, 2), 16);
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if (r === NaN || g === NaN || b === NaN)
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{
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return null;
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}
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return [ r, g, b ];
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}
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function validateColor(color)
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{
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if (!(color instanceof Array))
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{
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return false;
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}
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if (color.length !== 3)
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{
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return false;
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}
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if (typeof color[0] !== "number" ||
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typeof color[1] !== "number" ||
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typeof color[2] !== "number")
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{
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return false;
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}
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if (color[0] < 0 || color[0] > 255 ||
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color[1] < 0 || color[1] > 255 ||
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color[2] < 0 || color[2] > 255)
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{
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return false;
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}
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return true;
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}
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function createColorString(color)
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{
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if (!validateColor(color))
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{
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return null;
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}
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return "rgb(" + color[0].toString() + ", "
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+ color[1].toString() + ", "
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+ color[2].toString() + ")";
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}
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function setColor(ctx, color)
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{
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var colorSpec;
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if (color instanceof Array)
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{
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if (validateColor(color))
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{
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colorSpec = createColorString(color);
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}
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else
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{
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// error
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}
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}
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else
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{
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if (typeof color === "string")
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{
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colorSpec = color;
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}
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else
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{
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// error
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}
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}
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ctx.fillStyle = colorSpec;
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ctx.strokeStyle = colorSpec;
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}
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var SCALE_FACTOR = 0.7;
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var MIN_COLOR_VALUE = Math.floor(1.0 / (1.0 - SCALE_FACTOR));
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function lightenColor(color)
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{
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if (!validateColor(color))
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{
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return null;
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}
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// handle black directly, the result is NOT very much different but this is how it is
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// done in Java
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if (color[0] == 0 && color[1] == 0 && color[2] == 0)
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return [ MIN_COLOR_VALUE, MIN_COLOR_VALUE, MIN_COLOR_VALUE ];
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// force inputs to a minimim color value if between 0 and that minimum color value
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// (yes, this is how Java does it)
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var rIn = (color[0] > 0 && color[0] < MIN_COLOR_VALUE) ? MIN_COLOR_VALUE : color[0];
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var gIn = (color[1] > 0 && color[1] < MIN_COLOR_VALUE) ? MIN_COLOR_VALUE : color[1];
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var bIn = (color[2] > 0 && color[2] < MIN_COLOR_VALUE) ? MIN_COLOR_VALUE : color[2];
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// scale it
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var r = Math.min(Math.floor(rIn / SCALE_FACTOR), 255);
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var g = Math.min(Math.floor(gIn / SCALE_FACTOR), 255);
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var b = Math.min(Math.floor(bIn / SCALE_FACTOR), 255);
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return [ r, g, b ];
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}
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function darkenColor(color)
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{
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if (!validateColor(color))
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{
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return null;
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}
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var r = Math.max(0, Math.floor(color[0] * SCALE_FACTOR));
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var g = Math.max(0, Math.floor(color[1] * SCALE_FACTOR));
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var b = Math.max(0, Math.floor(color[2] * SCALE_FACTOR));
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return [ r, g, b ];
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}
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function create3DRect(ctx, x, y, width, height, fill, raised)
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{
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// save off our colors
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var oriFillColor = ctx.fillStyle;
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var oriStrokeColor = ctx.strokeStyle;
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// both colors should always be assigned the same value on entry to any drawing op
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// so it should be safe to use just the fill color
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var color = parseColor(oriFillColor);
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if (color === null)
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{
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return;
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}
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var darker = darkenColor(color);
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var lighter = lightenColor(color);
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// save off our state so that we can clear our clipping region on exit
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ctx.save();
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// the Java implementation draws 1 pixel larger in each dimension
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width = width + 1;
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height = height + 1;
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// setup our clipping region, this is needed because the line width (1 pixel wide) is
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// drawn half on one side of hte path and half on the other side; this makes paths a
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// half pixel bigger than the caller would expect; by defining the same path as a
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// clipping region, the half pixel width that is outside the path is never output
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ctx.beginPath();
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ctx.rect(x, y, width, height);
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ctx.clip();
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var current = raised ? lighter : darker;
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if (fill)
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ctx.fillStyle = createColorString(current);
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createRect(ctx, x, y, width, height, current, fill);
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// now begin a new path for the rectangle itself
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//ctx.beginPath();
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// create the path
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//ctx.rect(x, y, width, height);
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// set the color and fill or stroke as needed
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//if (fill)
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//{
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// ctx.fillStyle = createColorString(raised ? lighter : darker);
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// ctx.fill();
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//}
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//else
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//{
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// ctx.strokeStyle = createColorString(raised ? lighter : darker);
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// ctx.stroke();
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//}
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// draw the bottom and right sides in the contrasting color
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//ctx.strokeStyle = createColorString(raised ? darker : lighter);
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current = raised ? darker : lighter;
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//drawLine(x + 1, y + height, x + width, y + height);
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//drawLine(x + width, y, x + width, y + height - 1);
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rawLine(ctx, x + 1, y + height, x + width, y + height, current);
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rawLine(ctx, x + width, y, x + width, y + height - 1, current);
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// clear the clipping region
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ctx.restore();
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// reset our colors
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ctx.fillStyle = oriFillColor;
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ctx.strokeStyle = oriStrokeColor;
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}
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function createRect(ctx, x, y, width, height, color, fill)
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{
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// use vector operations for the interior of the rectangle
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if (fill)
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{
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ctx.beginPath();
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ctx.rect(x, y, width, height);
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renderClosedPath(ctx, fill);
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}
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// now overdraw the stroked portion
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rawLine(ctx, x, y, x + width, y, color);
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rawLine(ctx, x, y + 1, x, y + height, color);
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rawLine(ctx, x + width, y + 1, x + width, y + height, color);
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rawLine(ctx, x + 1, y + height, x + width - 1, y + height, color);
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}
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window.onload=function()
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{
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canvas = document.getElementById("bogus");
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ctx = canvas.getContext('2d');
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canvas.top = 150;
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canvas.left = 150;
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canvas.width = 600;
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canvas.height = 600;
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// canvas.style.backgroundColor = "#EEEEEE";
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// canvas.style.backgroundColor = "rbga(238, 238, 238, 1.0)";
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pixel = ctx.createImageData(1, 1);
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pixData = pixel.data;
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pixData[3] = 0xFF; // force alpha to 100% opaque
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ctx.globalCompositeOperation = "source-over";
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ctx.lineWidth = 1;
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ctx.imageSmoothingEnabled = false;
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ctx.translate(0.5, 0.5);
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var color;
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// draw background
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setColor(ctx, "#EEEEEE");
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color = parseColor(ctx.strokeStyle);
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createRect(ctx, 0, 0, canvas.width, canvas.height, color, true);
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// reset black as default color
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setColor(ctx, "#000000");
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color = parseColor(ctx.strokeStyle);
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var t;
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// draw Y axis tick marks
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for (t = 0; t < canvas.height; t++)
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{
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// major every 10 pixels
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if ((t % 10) == 0)
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{
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rawLine(ctx, 0, t, 5, t, color);
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}
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// minor every 2 pixels
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if ((t % 2) == 0)
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{
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rawLine(ctx, 0, t, 2, t, color);
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}
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}
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// draw X axis tick marks (can't start at 0 because the Y ticks are there)
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for (t = 10; t < canvas.width; t++)
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{
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// major every 10 pixels
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if ((t % 10) == 0)
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{
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rawLine(ctx, t, 0, t, 5, color);
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}
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// minor every 2 pixels
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if ((t % 2) == 0)
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{
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rawLine(ctx, t, 0, t, 2, color);
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}
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}
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rawLine(ctx, 10, 10, 590, 30, color);
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createRect(ctx, 40, 40, 55, 30, color, false);
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createRect(ctx, 150, 40, 55, 30, color, true);
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createRoundRect(ctx, 40, 90, 55, 30, 5, color, false);
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createRoundRect(ctx, 40, 130, 55, 30, 5, color, true);
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createRoundRect(ctx, 110, 90, 55, 30, 8, color, false);
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createRoundRect(ctx, 110, 130, 55, 30, 8, color, true);
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createRoundRect(ctx, 180, 90, 55, 30, 10, color, false);
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createRoundRect(ctx, 180, 130, 55, 30, 10, color, true);
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createRoundRect(ctx, 250, 90, 55, 30, 15, color, false);
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createRoundRect(ctx, 250, 130, 55, 30, 15, color, true);
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createRoundRect(ctx, 320, 90, 55, 30, 20, color, false);
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createRoundRect(ctx, 320, 130, 55, 30, 20, color, true);
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createRoundRect(ctx, 390, 90, 55, 30, 25, color, false);
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createRoundRect(ctx, 390, 130, 55, 30, 25, color, true);
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createRoundRect(ctx, 460, 90, 55, 30, 30, color, false);
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createRoundRect(ctx, 460, 130, 55, 30, 30, color, true);
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setColor(ctx, "#00FF00");
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color = parseColor(ctx.strokeStyle);
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create3DRect(ctx, 40, 175, 75, 30, false, true);
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create3DRect(ctx, 130, 175, 150, 60, false, true);
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create3DRect(ctx, 295, 175, 75, 30, true, true);
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create3DRect(ctx, 395, 175, 150, 60, true, true);
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create3DRect(ctx, 40, 250, 75, 30, false, false);
|
| 489 |
create3DRect(ctx, 130, 250, 150, 60, false, false);
|
| 490 |
create3DRect(ctx, 295, 250, 75, 30, true, false);
|
| 491 |
create3DRect(ctx, 395, 250, 150, 60, true, false);
|
| 492 |
setColor(ctx, "#000000");
|
| 493 |
color = parseColor(ctx.strokeStyle);
|
| 494 |
create3DRect(ctx, 40, 325, 75, 30, false, false);
|
| 495 |
create3DRect(ctx, 130, 325, 150, 60, false, false);
|
| 496 |
create3DRect(ctx, 295, 325, 75, 30, true, false);
|
| 497 |
create3DRect(ctx, 395, 325, 150, 60, true, false);
|
| 498 |
};
|
| 499 |
</script>
|
| 500 |
</head>
|
| 501 |
<body>
|
| 502 |
<canvas id="bogus" style="position:'absolute';">No HTML5 support in your browser!</canvas> |
| 503 |
</body>
|
| 504 |
</html>
|