HTML
<!DOCTYPE html>
<html>
<head>
<title>canvas</title>
</head>
<body>
<image src="bd_logo1.png" width='50' height='50' />
<canvas id='drawing' width="800" height="800" style="border:1px solid #c3c3c3;">A drawing of something.</canvas>
<canvas id="drawing2" width="800" height="300"></canvas>
<script type="text/javascript" src="canvas.js" ></script>
</body>
</html>
JS
//15.1 basic usage
var = document.getElementById Drawing ( 'Drawing');
// IF (drawing.getContext) {
// var context = drawing.getContext ( '2D');
// var imgURI = drawing.toDataURL ( ' Image / PNG ');
// Image var = document.createElement (' IMG ');
//'s image.src = imgURI;
// document.body.appendChild (Image);
//}
//15.2 2D context
//15.2 .1 fills and strokes
// determine browser supports <canvas> element
IF (drawing.getContext) {
var = drawing.getContext context ( "2D");
context.strokeStyle = 'Red';
context.fillStyle = '# 0000FF ';
context.stroke ();
}
//15.2.2 draw the rectangle
if (drawing.getContext) {
drawing.getContext context = var ( '2D');
/ *
* The document Mozilla
* HTTP: //developer.mozilla.org/en/docs/Cavans_tutorial: Basic_usage
* /
// Draw a red rectangle
context.strokeStyle = '# FF0000 ';
context.strokeRect (10, 10, 50, 50);
// draw a translucent blue rectangle
context.strokeStyle =' RGBA (0,0,255,0.5) ';
context.strokeRect (30, 30, 50, 50);
// Clear small rectangle where two small rectangles overlap
context.clearRect (40, 40, 10, 10);
}
//15.2.3 drawing a path
// arc (x, y, radius , startAngle, endAngle , counterclocwise)
// in (x, y) to draw an arc of a circle, radius of curvature radius of the start and end angle (in radians) are startAngle and endAngle.
// denotes startAngle counterclockwise and counterclockwise whether endAngle calculating a value of false for clockwise
// arcTo (x1, y1, x2 , y2, radius) // drawn from an arc start point to (x2, y2) so far, and through a given radius radius (X1, Y1)
// the working bezierCurveTo ( c1x, c1y, c2x, c2y, x, y) // draw a start point from the curve, the (x, y) so far, and in (c1x, c1y) and (c2x, c2y) control point
// lineTo ( x, y) from the start point to draw a straight line, the (x, y) so far.
// moveTo (x, y) to move the cursor to the drawing (x, y), does not draw a line
// quedraticCurveTo (cx, cy, x , y) from the start point to draw a quadratic curve, the (x, y) So far, and in (cx, cy) as control points
// rect (x, y, width , height) from the point (x, y) starts to draw a rectangle, the width and height are the width and height specified,
IF (drawing. the getContext) {
var = drawing.getContext context ( "2D");
// start path
context.beginPath ();
// draw outer
context.arc (100, 100, 99, 0, Math.PI * 2, false) ;
// draw the circle
context.moveTo (194,100);
context.arc (100,100,94,0,2 * Math.PI, to false);
// draw minute
context.moveTo (100,100);
context.lineTo (100, 15);
// draw hour
context.moveTo (100,100);
context.lineTo (35,100);
// stroke path
context.strokeStyle = '# FF0000';
context. Stroke ();
}
//15.2.4 draw text
IF (drawing.getContext) {
var = drawing.getContext context ( "2D");
context.font = 'Arial Bold 14px';
context.textAlign = 'Center';
context = .textBaseLine 'Middle';
context.fillText ( '12 is', 100,20);
// start point aligned
context.textAlign = 'Start';
context.fillText ( '12 is', 100,40);
// end aligned with
context .textAlign = 'end';
context .fillText ( '12', 100,60) ;
}
//15.2.5 transform
// rotate (angle) image rotation angle in radians about the origin
scaled image // scale (scaleX, scaleY), multiplied by sacelX in the x direction, the y direction by multiplying scaleY, sacelX, scaleY default value is 1.0
// Translate (x, y) to move to the origin of the coordinate (X, y), just after the transformation, the coordinates before becomes a (X, y) point corresponds to translational transform
// transform (m1_1, m1_m2, m2_1.m2_2 , dx, dy ) directly modify the transformation matrix multiplied with the following matrix
// m1_1 m1_2 DX
// M2_1 M2_2 Dy
// 0 0. 1;
// The above is a rotary + translation matrix, in fact, is to rotate at the origin, then the above-described translation dx dy is a 3 * 3 matrix
// Y1 siNA DX
@ X1 Cosa Dy
@ 0 0. 1 this is probably somewhat forgotten matrix
// assumed that the x-axis x1: 100, y1: 0 rotated clockwise by 90 ° trigonometric seek X2, Y2
// = the Math.sqrt X2 (X1 * Y1 + 2 * 2) * Math.sqrt Cosa Y2 = (X1 + Y1 * 2 * 2) * siNA
// rotation 90 just x2 = 0 y2 = 100
// translation transform using the drawing
if (drawing.getContext) {
drawing.getContext context = var ( "2D");
context.translate (200,200); // use painted before the first translational avoiding, to distinguish. Translation is superimposed.
context.moveTo (0,0);
// start path
context.beginPath ();
// Painter cylindrical
context.arc (100,100,99,0,2 * Math.PI, false) ; // location of the center is actually 200 + 100
within // Draw a circle
context .moveTo (194,100); // brush starting point for translational direction x 6 units
context.arc (100,100,94,0,2 * Math.PI, false) ; // center unchanged, drawing concentric circles, radius and narrow brush 6 position coincide.
// conversion origin
context.translate (100,100); // center position becomes 200 + 100 + 100 = 400
// rotating hands
context.rotate (1); // rotation of 90 degrees, behind the painting coordinate unfinished normal after rotating 90
// draw minute
context.moveTo (0,0); // here lineTo (0,0) actually go to the absolute origin of 300, 300
context.lineTo (0, -85);
// draw hour
context.lineTo (-65,0);
// stroke path
context.stroke ();
//context.restore (); then save the results and return disposed forward
}
//15.2.6 drawn image
var Image = the document.images [0];
//context.drawImage(image,10,10); // draw a picture to which actual position is then rotated by 90 and 310, 310 because of the above rotated 90
context.drawImage (image, 10,10,50,50); // specified WH
//context.drawImage () source image up to nine parameters to be rendered, the source image coordinates x, y coordinates of the source image, the source image width, the height of the source image, the target image of a target image x y, the width of the target image, the target image height
//15.2.7 shadow
var drawing2 = document.getElementById ( 'drawing2');
var = context2 drawing2.getContext ( '2D') ;
// set the shadow
context2.shadowOffsetX =. 5;
context2.shadowOffsetY =. 5;
context2.shadowBlur =. 4;
context2.shadowColor = 'RGBA (0,0,0,0.5)';
// draw a blue rectangle
context2.fillStyle = 'rgba (0,0,255,1)' ;
// draw a red rectangle
= context2.fillStyle '# FF0000';
context2.fillRect (10,10,50,50);
// Image.width=50;
context2.fillRect (30,30,50,50);
//15.2.8 gradient
var gradient1 = context2.createLinearGradient (50,50,70,70);
gradient1.addColorStop (0, 'White');
gradient1.addColorStop ( . 1, 'Black');
var = gradient2 context2.createRadialGradient (125,125,10,125,125,30); // gradient concentrically outwardly
gradient2.addColorStop (0, 'White');
gradient2.addColorStop (. 1, 'Black');
// draw a rectangle gradient
context2.fillStyle = gradient1;
context2.fillRect (50,50,50,50);
context2.fillStyle = gradient2;
context2.fillRect (100,100,50,50);
//context2.stroke ();
/ /15.2.9 mode
var Image = the document.images [0];
// image.height = 50;
context2.createPattern pattern = var (Image, 'REPEAT'); // REPEAT REPEAT REPEAT-X-Y-NO REPEAT
context2.fillStyle = pattern;
context2.fillRect (200,200,150,150);
//15.2.10 using image data
var imageData = context2.getImageData (100,100,50,50); // coordinate position acquired region width and length of the data
var = data imageData.data;
var = Red data [0], data = Green [. 1], data = Blue [2 ], Alpha = data [. 3];
data [0] = 255; // set the image data
imageData.data = data;
context2.putImageData (the imageData, 0,0); // write the image data to the position
//15.2.11 synthesis
context2.globaAlpha = 0.5;