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This article is about how to use html5 canvas to make graffiti drawing boards. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Empty the drawing board

Line width: 1

three

five

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eleven

Color: black

Blue

Red

Green

Yellow

Gray

HTML code

We need a canvas element for painting and some drop-down boxes for the selection operation:

JAVASCRIPT

Our graffiti artboard js script has three main functions:

InitThis (): this method is used to initialize the required mouse events.

Draw (): this method draws a line each time the left mouse button is pressed.

ClearArea (): this method is used to empty all lines on the artboard.

Var mousePressed = false

Var lastX, lastY

Var ctx

Function InitThis () {

Ctx = document.getElementById ('myCanvas'). GetContext ("2d")

$('# myCanvas') .mousedown (function (e) {

MousePressed = true

Draw (e.pageX-$(this). Offset (). Left, e.pageY-$(this). Offset (). Top, false)

})

$('# myCanvas') .mousemove (function (e) {

If (mousePressed) {

Draw (e.pageX-$(this). Offset (). Left, e.pageY-$(this). Offset (). Top, true)

}

})

$('# myCanvas') .mouseup (function (e) {

MousePressed = false

})

$('# myCanvas') .mouseleave (function (e) {

MousePressed = false

})

}

Function Draw (x, y, isDown) {

If (isDown) {

Ctx.beginPath ()

Ctx.strokeStyle = $('# selColor') .val ()

Ctx.lineWidth = $('# selWidth') .val ()

Ctx.lineJoin = "round"

Ctx.moveTo (lastX, lastY)

Ctx.lineTo (x, y)

Ctx.closePath ()

Ctx.stroke ()

}

LastX = x; lastY = y

}

Function clearArea () {

/ / Use the identity matrix while clearing the canvas

Ctx.setTransform (1,0,0,1,0,0)

Ctx.clearRect (0,0, ctx.canvas.width, ctx.canvas.height)

}

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