I have these event listeners in my code
canvas.addEventListener('mousemove', onMouseMove, false);
canvas.addEventListener('mousedown', onMouseDown,false);
canvas.addEventListener('mouseup', onMouseUp, false);
These functions will help me to pan the canvas. I have declared a variable in the onLoad called pan, isDown, mousePostion and previous mouse positions. Then in the initialise function is set the pan,mousePos and premousepos to vectors containing 0,0
function draw() {
context.translate(pan.getX(), pan.getY());
topPerson.draw(context);
console.log(pan);
}
function onMouseDown(event) {
var x = event.offsetX;
var y = event.offsetY;
var mousePosition = new vector(event.offsetX, event.offsetY);
previousMousePosition = mousePosition;
isDown = true;
console.log(previousMousePosition);
console.log("onmousedown" + "X coords: " + x + ", Y coords: " + y);
}
function onMouseUp(event) {
isDown = false;
}
function onMouseMove(event) {
if (isDown) {
console.log(event.offsetX);
mousePosition = new vector(event.offsetX, event.offsetY);
newMousePosition = mousePosition;
console.log('mouseMove' + newMousePosition);
var panX = newMousePosition.getX() - previousMousePosition.getX();
var panY = newMousePosition.getY() - previousMousePosition.getY();
console.log('onMouseMove: ' + panX);
pan = new vector(panX, panY);
console.log('mouseMove' + pan);
}
}
But it is not registering the new pan Values so you could attempt to drag the canvas. I know my mouse dragging events work but is just doesnt pan.
Here's a simple (annotated) example of panning code
It works by accumulating the net amount the mouse has been dragged horizontally (and vertically) Then it redraws everything, but offset by those accumulated horizontal & vertical distances.
Example code and a Demo:
// canvas related variables
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
// account for scrolling
function reOffset(){
var BB=canvas.getBoundingClientRect();
offsetX=BB.left;
offsetY=BB.top;
}
var offsetX,offsetY;
reOffset();
window.onscroll=function(e){ reOffset(); }
window.onresize=function(e){ reOffset(); }
// mouse drag related variables
var isDown=false;
var startX,startY;
// the accumulated horizontal(X) & vertical(Y) panning the user has done in total
var netPanningX=0;
var netPanningY=0;
// just for demo: display the accumulated panning
var $results=$('#results');
// draw the numbered horizontal & vertical reference lines
for(var x=0;x<100;x++){ ctx.fillText(x,x*20,ch/2); }
for(var y=-50;y<50;y++){ ctx.fillText(y,cw/2,y*20); }
// listen for mouse events
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
$("#canvas").mouseout(function(e){handleMouseOut(e);});
function handleMouseDown(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// calc the starting mouse X,Y for the drag
startX=parseInt(e.clientX-offsetX);
startY=parseInt(e.clientY-offsetY);
// set the isDragging flag
isDown=true;
}
function handleMouseUp(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// clear the isDragging flag
isDown=false;
}
function handleMouseOut(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// clear the isDragging flag
isDown=false;
}
function handleMouseMove(e){
// only do this code if the mouse is being dragged
if(!isDown){return;}
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// get the current mouse position
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// dx & dy are the distance the mouse has moved since
// the last mousemove event
var dx=mouseX-startX;
var dy=mouseY-startY;
// reset the vars for next mousemove
startX=mouseX;
startY=mouseY;
// accumulate the net panning done
netPanningX+=dx;
netPanningY+=dy;
$results.text('Net change in panning: x:'+netPanningX+'px, y:'+netPanningY+'px');
// display the horizontal & vertical reference lines
// The horizontal line is offset leftward or rightward by netPanningX
// The vertical line is offset upward or downward by netPanningY
ctx.clearRect(0,0,cw,ch);
for(var x=-50;x<50;x++){ ctx.fillText(x,x*20+netPanningX,ch/2); }
for(var y=-50;y<50;y++){ ctx.fillText(y,cw/2,y*20+netPanningY); }
}
body{ background-color: ivory; }
#canvas{border:1px solid red; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<h4 id=results>Drag the mouse to see net panning in x,y directions</h4>
<canvas id="canvas" width=300 height=150></canvas>
To answer question
You have not provided some of the code. Specifically the vector object you are creating each event, could be there. (really you should not be creating a new object each time. Create once and update the values)
What I do see is that mouseMove events do not update the previous mouse position object so you will only get panning from the last mouse down. But you may want that. So without the code I don't know what is wrong as the code given is OK.
Below is how I do the whole shabang..
How to pan (and zoom).
Below is an example of panning and zooming with the mouse. Its a little more complex than standard pan and zooms, that is because I have added some smoothing to the pan and zoom to give it a better interactive feel.
How it works.
The canvas uses a transformation matrix to transform points. What this does is maintain that matrix. I call the transformed space, real space. I also maintain an inverse matrix, that is used to convert from screen space into real space.
The core of the demo is around the object displayTransform it holds the matrix, all the individual values needed, and the functions update() call once a frame, setHome() get the screen space transform and applies it to the canvas. Used to clear the screen. And setTransform() this set the canvas to real space (the zoomed panned space)
To smooth out movements I have a mirror of the values x, y, ox, oy, scale, and rotate. ((ox,oy) are origin x and y) (and yes rotate works) each of these variable has a delta prefixed with d and a chaser prefixed with c. The chaser values chase the required values. You should not touch the chaser values. There are two values called drag and accel (short for acceleration) drag (not real simulated drag) is how quickly the deltas decay. Values for drag > 0.5 will result in a bouncy response. As you get toward one it will get more and more bouncy. At 1 the bound will not stop, above one and it's unusable. 'accel' is how quickly the transform responds to mouse movement. Low values are slow response, 0 is no response at all, and one is instant response. Play with the values to find what you like.
Example of the logic for chaser values
var x = 100; // the value to be chased
var dx = 0; // the delta x or the change in x per frame
var cx = 0; // the chaser value. This value chases x;
var drag = 0.1; // quick decay
var accel = 0.9; // quick follpw
// logic
dx += (x-cx)*accel; // get acceleration towards x
dx *= drag; // apply the drag
cx += dx; // change chaser by delta x.
Convert coords
No point having a zoom panned rotated canvas if you don't know where things are. To do this I keep an inverse matrix. It converts screen x and y into realspace x and y. For convenience I convert the mouse to real space every update. If you want the reverse realSpace to screen space. then its just
var x; // real x coord (position in the zoom panned rotate space)
var y; // real y coord
// "this" is displayTransform
x -= this.cx;
y -= this.cy;
// screenX and screen Y are the screen coordinates.
screenX = (x * this.matrix[0] + y * this.matrix[2])+this.cox;
screenY = (x * this.matrix[1] + y * this.matrix[3])+this.coy;
You can see it at the end of the mouse displayTransform.update where I use the inverse transform to convert the mouse screen coords to real coords. Then in the main update loop I use the mouse real coords to display the help text. I leave it up to the user of the code to create a function that will convert any screen coord. (easy just pinch the bit where the mouse is being converted).
Zoom
The zoom is done with the mouse wheel. This presents a bit of a problem and naturally you expect the zoom to be centered on the mouse. But the transform is actually relative to the top left of the screen. To fix this I also keep an origin x and y. This basically floats about until the wheel zoom is needed then it is set to the mouse real position, and the mouse distance from the top left is placed in the transform x and y position. Then just increase or decrease the scale to zoom in and out. I have left the origin and offset to float (not set the chase values) this works for the current drag and acceleration setting but if you notice that it's not working that well with other setting set the the cx, cy, cox, coy values as well. ( I have added a note in the code)
Pan
Pan is done with the left mouse button. Click and drag to pan. This is straight forward. I get the difference between the last mouse position and the new one screen space (the coords given by the mouse events) This gives me a mouse delta vector. I transform the delta mouse vector into real space and subtract that from the top left coords displayTransform.x and displayTransform.y. Thats it I let the chaser x and y smooth it all out.
The snippet just displays a large image that can be panned and zoomed. I check for the complete flag rather than use onload. While the image is loading the snippet will just display loading. The main loop is refreshed with requestAnimationFrame, first I update the displayTransform then the canvas is cleared in home space (screen space) and then the image is displayed in real space. As always I a fighting time so will return as time permits to add more comments, and maybe a function or two.
If you find the chase variables a little to much, you can just remove them and replace all the c prefixed vars with the unprefixed ones.
OK hope this helps. Not done yet as need to clean up but need to do some real work for a bit.
var canvas = document.getElementById("canV");
var ctx = canvas.getContext("2d");
var mouse = {
x : 0,
y : 0,
w : 0,
alt : false,
shift : false,
ctrl : false,
buttonLastRaw : 0, // user modified value
buttonRaw : 0,
over : false,
buttons : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
};
function mouseMove(event) {
mouse.x = event.offsetX;
mouse.y = event.offsetY;
if (mouse.x === undefined) {
mouse.x = event.clientX;
mouse.y = event.clientY;
}
mouse.alt = event.altKey;
mouse.shift = event.shiftKey;
mouse.ctrl = event.ctrlKey;
if (event.type === "mousedown") {
event.preventDefault()
mouse.buttonRaw |= mouse.buttons[event.which-1];
} else if (event.type === "mouseup") {
mouse.buttonRaw &= mouse.buttons[event.which + 2];
} else if (event.type === "mouseout") {
mouse.buttonRaw = 0;
mouse.over = false;
} else if (event.type === "mouseover") {
mouse.over = true;
} else if (event.type === "mousewheel") {
event.preventDefault()
mouse.w = event.wheelDelta;
} else if (event.type === "DOMMouseScroll") { // FF you pedantic doffus
mouse.w = -event.detail;
}
}
function setupMouse(e) {
e.addEventListener('mousemove', mouseMove);
e.addEventListener('mousedown', mouseMove);
e.addEventListener('mouseup', mouseMove);
e.addEventListener('mouseout', mouseMove);
e.addEventListener('mouseover', mouseMove);
e.addEventListener('mousewheel', mouseMove);
e.addEventListener('DOMMouseScroll', mouseMove); // fire fox
e.addEventListener("contextmenu", function (e) {
e.preventDefault();
}, false);
}
setupMouse(canvas);
// terms.
// Real space, real, r (prefix) refers to the transformed canvas space.
// c (prefix), chase is the value that chases a requiered value
var displayTransform = {
x:0,
y:0,
ox:0,
oy:0,
scale:1,
rotate:0,
cx:0, // chase values Hold the actual display
cy:0,
cox:0,
coy:0,
cscale:1,
crotate:0,
dx:0, // deltat values
dy:0,
dox:0,
doy:0,
dscale:1,
drotate:0,
drag:0.1, // drag for movements
accel:0.7, // acceleration
matrix:[0,0,0,0,0,0], // main matrix
invMatrix:[0,0,0,0,0,0], // invers matrix;
mouseX:0,
mouseY:0,
ctx:ctx,
setTransform:function(){
var m = this.matrix;
var i = 0;
this.ctx.setTransform(m[i++],m[i++],m[i++],m[i++],m[i++],m[i++]);
},
setHome:function(){
this.ctx.setTransform(1,0,0,1,0,0);
},
update:function(){
// smooth all movement out. drag and accel control how this moves
// acceleration
this.dx += (this.x-this.cx)*this.accel;
this.dy += (this.y-this.cy)*this.accel;
this.dox += (this.ox-this.cox)*this.accel;
this.doy += (this.oy-this.coy)*this.accel;
this.dscale += (this.scale-this.cscale)*this.accel;
this.drotate += (this.rotate-this.crotate)*this.accel;
// drag
this.dx *= this.drag;
this.dy *= this.drag;
this.dox *= this.drag;
this.doy *= this.drag;
this.dscale *= this.drag;
this.drotate *= this.drag;
// set the chase values. Chase chases the requiered values
this.cx += this.dx;
this.cy += this.dy;
this.cox += this.dox;
this.coy += this.doy;
this.cscale += this.dscale;
this.crotate += this.drotate;
// create the display matrix
this.matrix[0] = Math.cos(this.crotate)*this.cscale;
this.matrix[1] = Math.sin(this.crotate)*this.cscale;
this.matrix[2] = - this.matrix[1];
this.matrix[3] = this.matrix[0];
// set the coords relative to the origin
this.matrix[4] = -(this.cx * this.matrix[0] + this.cy * this.matrix[2])+this.cox;
this.matrix[5] = -(this.cx * this.matrix[1] + this.cy * this.matrix[3])+this.coy;
// create invers matrix
var det = (this.matrix[0] * this.matrix[3] - this.matrix[1] * this.matrix[2]);
this.invMatrix[0] = this.matrix[3] / det;
this.invMatrix[1] = - this.matrix[1] / det;
this.invMatrix[2] = - this.matrix[2] / det;
this.invMatrix[3] = this.matrix[0] / det;
// check for mouse. Do controls and get real position of mouse.
if(mouse !== undefined){ // if there is a mouse get the real cavas coordinates of the mouse
if(mouse.oldX !== undefined && (mouse.buttonRaw & 1)===1){ // check if panning (middle button)
var mdx = mouse.x-mouse.oldX; // get the mouse movement
var mdy = mouse.y-mouse.oldY;
// get the movement in real space
var mrx = (mdx * this.invMatrix[0] + mdy * this.invMatrix[2]);
var mry = (mdx * this.invMatrix[1] + mdy * this.invMatrix[3]);
this.x -= mrx;
this.y -= mry;
}
// do the zoom with mouse wheel
if(mouse.w !== undefined && mouse.w !== 0){
this.ox = mouse.x;
this.oy = mouse.y;
this.x = this.mouseX;
this.y = this.mouseY;
/* Special note from answer */
// comment out the following is you change drag and accel
// and the zoom does not feel right (lagging and not
// zooming around the mouse
/*
this.cox = mouse.x;
this.coy = mouse.y;
this.cx = this.mouseX;
this.cy = this.mouseY;
*/
if(mouse.w > 0){ // zoom in
this.scale *= 1.1;
mouse.w -= 20;
if(mouse.w < 0){
mouse.w = 0;
}
}
if(mouse.w < 0){ // zoom out
this.scale *= 1/1.1;
mouse.w += 20;
if(mouse.w > 0){
mouse.w = 0;
}
}
}
// get the real mouse position
var screenX = (mouse.x - this.cox);
var screenY = (mouse.y - this.coy);
this.mouseX = this.cx + (screenX * this.invMatrix[0] + screenY * this.invMatrix[2]);
this.mouseY = this.cy + (screenX * this.invMatrix[1] + screenY * this.invMatrix[3]);
mouse.rx = this.mouseX; // add the coordinates to the mouse. r is for real
mouse.ry = this.mouseY;
// save old mouse position
mouse.oldX = mouse.x;
mouse.oldY = mouse.y;
}
}
}
// image to show
var img = new Image();
img.src = "https://upload.wikimedia.org/wikipedia/commons/e/e5/Fiat_500_in_Emilia-Romagna.jpg"
// set up font
ctx.font = "14px verdana";
ctx.textAlign = "center";
ctx.textBaseline = "middle";
// timer for stuff
var timer =0;
function update(){
timer += 1; // update timere
// update the transform
displayTransform.update();
// set home transform to clear the screem
displayTransform.setHome();
ctx.clearRect(0,0,canvas.width,canvas.height);
// if the image loaded show it
if(img.complete){
displayTransform.setTransform();
ctx.drawImage(img,0,0);
ctx.fillStyle = "white";
if(Math.floor(timer/100)%2 === 0){
ctx.fillText("Left but to pan",mouse.rx,mouse.ry);
}else{
ctx.fillText("Wheel to zoom",mouse.rx,mouse.ry);
}
}else{
// waiting for image to load
displayTransform.setTransform();
ctx.fillText("Loading image...",100,100);
}
if(mouse.buttonRaw === 4){ // right click to return to homw
displayTransform.x = 0;
displayTransform.y = 0;
displayTransform.scale = 1;
displayTransform.rotate = 0;
displayTransform.ox = 0;
displayTransform.oy = 0;
}
// reaquest next frame
requestAnimationFrame(update);
}
update(); // start it happening
.canC { width:400px; height:400px;}
div {
font-size:x-small;
}
<div>Wait for image to load and use <b>left click</b> drag to pan, and <b>mouse wheel</b> to zoom in and out. <b>Right click</b> to return to home scale and pan. Image is 4000 by 2000 plus so give it time if you have a slow conection. Not the tha help text follows the mouse in real space. Image from wiki commons</div>
<canvas class="canC" id="canV" width=400 height=400></canvas>
Related
I want to use Draw with Mouse on the canvas. The code is as follows:
// Stores the initial position of the cursor
let coord = {x:0 , y:0};
// // set a flag
let paint = false;
// Updates the coordianates of the cursor when an event e is triggered
function getPosition(event){
coord.x = event.clientX - canvas.offsetLeft;
coord.y = event.clientY - canvas.offsetTop;
}
// The following functions toggle the flag to start and stop drawing
function startPainting(event){
if (mouseID.checked){
myCanvas.style.cursor = "url('/paint.cur'),auto"
paint = true;
getPosition(event);
}
}
function stopPainting(){
paint = false;
}
function sketch(event){
if (!paint) return;
ctx.beginPath();
ctx.lineWidth = mouseline.value;
// set to a round shape.
ctx.lineCap = "round";
ctx.strokeStyle = bcolor.value;
// The cursor to start drawing
ctx.moveTo(coord.x, coord.y);
// The position of the cursor gets updated when move the mouse around.
getPosition(event);
ctx.lineTo(coord.x , coord.y);
// Draws the line.
ctx.stroke();
}
The problem is when I run it on my desktop the mouse is fine but on another computer, the mouse gets a mismatched position with the drawing. Can anyone help me with the issue?
I have a simple function which the user can click and drag the camera. The camera moves with a slight smoothness, but i do not know a simple way to stop the camera once it has caught up to the mouse position.
I'm sure it's just a simple maths logic error, but currently the camera just keeps floating off forever.
This is my function:
function drag(evt,el){
clearInterval(timer);
if(evt.button == 2){ //right click and drag
mousePos = {};
mousePos.x = evt.offsetX / scale;
mousePos.y = evt.offsetY / scale;
function update(e){
var difx = mousePos.x - (e.offsetX/scale),
dify = mousePos.y - (e.offsetY/scale);
var targetX = camera.x + difx;
var targetY = camera.y + dify;
//update for next mouse movement
mousePos.x = e.offsetX / scale;
mousePos.y = e.offsetY / scale;
function smooth(){ // the problems lay here
if(camera.x != targetX){
camera.x += (difx * lerp);
}
if(camera.y != targetY){
camera.y += (dify * lerp);
}
}
timer = setInterval(smooth,16);
}
function clear(){
el.removeEventListener('mousemove', update, false);
this.removeEventListener('mouseup', clear, false);
}
el.addEventListener('mousemove',update,false);
document.body.addEventListener('mouseup',clear,false);
}}
I have the code in action here http://jsfiddle.net/bbb9q2c3/ if you click and drag then let go the box will keep moving because my current code does not seem to detect when the camera has reached it's target.
What can i do to solve this issue?
I fiddled with this a bit.
Here's what I changed:
In the draw function I removed translate, so that the camera coordinates match mouse coordinates. So camera with (0,0) is at the top left and not middle.
Use threshold to check if camera is near the mouse ath.abs(dify) > 1.
Added clearInterval to update function. It is less responsive now, so you may want to fiddle with that.
Set square to the middle position in the initialization.
I'm drawing an image onto a canvas using drawImage. It's a PNG that is surrounded by transparent pixels, like this:
How can I add a solid-colored border to the visible part of that image on the canvas? To clarify: I don't want a rectangle that surrounds the image's bounding box. The border should go around the grass patch.
I did consider using shadows, but I don't really want a glowing border, I want a solid one.
A bit late, but just draw the image offset which is much faster than analyzing the edges:
var ctx = canvas.getContext('2d'),
img = new Image;
img.onload = draw;
img.src = "http://i.stack.imgur.com/UFBxY.png";
function draw() {
var dArr = [-1,-1, 0,-1, 1,-1, -1,0, 1,0, -1,1, 0,1, 1,1], // offset array
s = 2, // thickness scale
i = 0, // iterator
x = 5, // final position
y = 5;
// draw images at offsets from the array scaled by s
for(; i < dArr.length; i += 2)
ctx.drawImage(img, x + dArr[i]*s, y + dArr[i+1]*s);
// fill with color
ctx.globalCompositeOperation = "source-in";
ctx.fillStyle = "red";
ctx.fillRect(0,0,canvas.width, canvas.height);
// draw original image in normal mode
ctx.globalCompositeOperation = "source-over";
ctx.drawImage(img, x, y);
}
<canvas id=canvas width=500 height=500></canvas>
==> ==>
First, attributions:
As #Philipp says, you'll need to analyze pixel data to get your outline border.
You can use the "Marching Squares" algorithm to determine which transparent pixels border the non-transparent grass pixels. You can read more about the Marching Squares algorithm here: http://en.wikipedia.org/wiki/Marching_squares
Michael Bostock has a very nice plugin version of Marching Squares in his d3 data visualization application (IMHO, d3 is the best open-source data visualization program available). Here's a link to the plugin: https://github.com/d3/d3-plugins/tree/master/geom/contour
You can outline the border of your grass image like this:
Draw your image on the canvas
Grab the image's pixel data using .getImageData
Configure the plug-in to look for transparent pixels bordering opaque pixels
// This is used by the marching ants algorithm
// to determine the outline of the non-transparent
// pixels on the image using pixel data
var defineNonTransparent=function(x,y){
var a=data[(y*cw+x)*4+3];
return(a>20);
}
Call the plugin which returns a set of points which outline the border of your image.
// call the marching ants algorithm
// to get the outline path of the image
// (outline=outside path of transparent pixels
points=geom.contour(defineNonTransparent);
Use the set of points to draw a path around your image.
Here's annotated code and a Demo:
// Marching Squares Edge Detection
// this is a "marching ants" algorithm used to calc the outline path
(function() {
// d3-plugin for calculating outline paths
// License: https://github.com/d3/d3-plugins/blob/master/LICENSE
//
// Copyright (c) 2012-2014, Michael Bostock
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//* Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//* Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//* The name Michael Bostock may not be used to endorse or promote products
// derived from this software without specific prior written permission.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MICHAEL BOSTOCK BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
geom = {};
geom.contour = function(grid, start) {
var s = start || d3_geom_contourStart(grid), // starting point
c = [], // contour polygon
x = s[0], // current x position
y = s[1], // current y position
dx = 0, // next x direction
dy = 0, // next y direction
pdx = NaN, // previous x direction
pdy = NaN, // previous y direction
i = 0;
do {
// determine marching squares index
i = 0;
if (grid(x-1, y-1)) i += 1;
if (grid(x, y-1)) i += 2;
if (grid(x-1, y )) i += 4;
if (grid(x, y )) i += 8;
// determine next direction
if (i === 6) {
dx = pdy === -1 ? -1 : 1;
dy = 0;
} else if (i === 9) {
dx = 0;
dy = pdx === 1 ? -1 : 1;
} else {
dx = d3_geom_contourDx[i];
dy = d3_geom_contourDy[i];
}
// update contour polygon
if (dx != pdx && dy != pdy) {
c.push([x, y]);
pdx = dx;
pdy = dy;
}
x += dx;
y += dy;
} while (s[0] != x || s[1] != y);
return c;
};
// lookup tables for marching directions
var d3_geom_contourDx = [1, 0, 1, 1,-1, 0,-1, 1,0, 0,0,0,-1, 0,-1,NaN],
d3_geom_contourDy = [0,-1, 0, 0, 0,-1, 0, 0,1,-1,1,1, 0,-1, 0,NaN];
function d3_geom_contourStart(grid) {
var x = 0,
y = 0;
// search for a starting point; begin at origin
// and proceed along outward-expanding diagonals
while (true) {
if (grid(x,y)) {
return [x,y];
}
if (x === 0) {
x = y + 1;
y = 0;
} else {
x = x - 1;
y = y + 1;
}
}
}
})();
//////////////////////////////////////////
// canvas related variables
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
// checkbox to show/hide the original image
var $showImage=$("#showImage");
$showImage.prop('checked', true);
// checkbox to show/hide the path outline
var $showOutline=$("#showOutline");
$showOutline.prop('checked', true);
// an array of points that defines the outline path
var points;
// pixel data of this image for the defineNonTransparent
// function to use
var imgData,data;
// This is used by the marching ants algorithm
// to determine the outline of the non-transparent
// pixels on the image
var defineNonTransparent=function(x,y){
var a=data[(y*cw+x)*4+3];
return(a>20);
}
// load the image
var img=new Image();
img.crossOrigin="anonymous";
img.onload=function(){
// draw the image
// (this time to grab the image's pixel data
ctx.drawImage(img,canvas.width/2-img.width/2,canvas.height/2-img.height/2);
// grab the image's pixel data
imgData=ctx.getImageData(0,0,canvas.width,canvas.height);
data=imgData.data;
// call the marching ants algorithm
// to get the outline path of the image
// (outline=outside path of transparent pixels
points=geom.contour(defineNonTransparent);
ctx.strokeStyle="red";
ctx.lineWidth=2;
$showImage.change(function(){ redraw(); });
$showOutline.change(function(){ redraw(); });
redraw();
}
img.src="http://i.imgur.com/QcxIJxa.png";
// redraw the canvas
// user determines if original-image or outline path or both are visible
function redraw(){
// clear the canvas
ctx.clearRect(0,0,canvas.width,canvas.height);
// draw the image
if($showImage.is(':checked')){
ctx.drawImage(img,canvas.width/2-img.width/2,canvas.height/2-img.height/2);
}
// draw the path (consisting of connected points)
if($showOutline.is(':checked')){
// draw outline path
ctx.beginPath();
ctx.moveTo(points[0][0],points[0][4]);
for(var i=1;i<points.length;i++){
var point=points[i];
ctx.lineTo(point[0],point[1]);
}
ctx.closePath();
ctx.stroke();
}
}
body{ background-color: ivory; }
canvas{border:1px solid red;}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<input type="checkbox" id="showImage" />Show Image<br>
<input type="checkbox" id="showOutline" />Show Outline Path<br>
<canvas id="canvas" width=300 height=450></canvas>
I was looking for a way to do this and it seems there are only laborious solutions.
I came up with a little workaround using shadows and a loop to display them all around the image:
// Shadow color and blur
// To get a blurry effect use rgba() with a low opacity as it will be overlaid
context.shadowColor = "red";
context.shadowBlur = 0;
// X offset loop
for(var x = -2; x <= 2; x++){
// Y offset loop
for(var y = -2; y <= 2; y++){
// Set shadow offset
context.shadowOffsetX = x;
context.shadowOffsetY = y;
// Draw image with shadow
context.drawImage(img, left, top, width, height);
}
}
I'd like to make an app where a ball moves at the angle your mouse hits it. So if you swipe your mouse down from top left quadrant at 30 degrees (I guess that would be 180-30 = angle of 150 degrees), it will knock the ball that way. I've been drawing my lines as such:
function drawAngles () {
var d = 50; //start line at (10, 20), move 50px away at angle of 30 degrees
var angle = 80 * Math.PI/180;
ctx.beginPath();
ctx.moveTo(300,0);
ctx.lineTo(300,600); //x, y
ctx.moveTo(0,300);
ctx.lineTo(600,300);
ctx.moveTo(300,300);
ctx.lineTo(600,100);
ctx.arc(300,300,300,0,2*Math.PI);
ctx.stroke();
}
But this doesn't give me an idea of what the angles are.
Then I move the ball at that angle (for now, I'm animating it without mouse interaction)
function getAngleX (x) {
return x = x + (50 * Math.cos(Math.PI/6));
}
function getAngleY(y) {
return y = y + (50 * Math.sin(Math.PI/6));
}
//just animate this box to move at an angle from center down at 30 degrees
$(".anotherBox").mouseenter(function(e) {
pos = $(this).position();
box2X = pos.left;
box2Y = pos.top;
$(this).animate({
//top : $(window).outerHeight(),
top : getAngleY(box2Y)+"px",
left: getAngleX(box2X)+"px",
}, "slow");
});
So how can I draw a line at a specified angle? I'd like to make sure my ball is following along that path.
You can use different approaches to achieve this but if you want to use the same basis to move and draw then this approach may suit well.
First we use a function to get step values for x and y based on the angle (in radians):
function getSteps(angle) {
var cos = Math.cos(angle),
sin = Math.sin(angle);
return {
x: cos -sin,
y: sin + cos
}
}
Then using these steps values we can scale them to get an end point, or scale them gradually to animate an object along the line. A simple loop could look like this (just for example):
function loop() {
var x = i * step.x, // scale using i
y = i * step.y;
ctx.fillRect(200 + x, 200 + y, 2, 2); // add to origin start point 200, 200
i += 1; // increase i
if (i < length) requestAnimationFrame(loop);
}
Live demo
If you just want to draw a line at a certain angle you can do the following instead:
function lineAtAngle(x1, y1, length, angle) {
ctx.moveTo(x1, y1);
ctx.lineTo(x1 + length * Math.cos(angle), y1 + length * Math.sin(angle));
}
then stroke it.
Hope this helps!
If i guess right, i think you want the mouse act like a baseball bat, and you need to measure the current mouse angle, that is to store previous mouse position and do some math.
You have also to keep track if you allready handled current collision, to avoid the ball being 'sticky' and follow the mouse.
http://jsfiddle.net/gamealchemist/z3U8g/
var ctx = cv.getContext('2d');
var ball = {
x:200, y:200,
r : 30,
vx : 0.4, vy:0.4
}
// when mouse moved that distance, ball speed norm will be 1
var speedNorm = 10;
var collisionOnGoing = false;
function collide() {
var dist = sq(ball.x - mx) + sq (ball.y-my);
// too far from ball ?
if (dist > sq(ball.r)) {
collisionOnGoing = false;
return;
}
// return if collision allready handled
if (collisionOnGoing) return;
var mouseDist =Math.sqrt( sq(mx-lastmx) + sq(my-lastmy) );
// no collision if mouse too slow
if (mouseDist<speedNorm/5) return;
// launch the ball in current direction
// with a speed relative to the mouse speed.
var mouseAngle = Math.atan2(my-lastmy, mx-lastmx);
ball.vx= (mouseDist / speedNorm ) * Math.cos(mouseAngle);
ball.vy= (mouseDist / speedNorm ) * Math.sin(mouseAngle);
collisionOnGoing = true;
}
function animate() {
requestAnimationFrame(animate);
ctx.clearRect(0,0,400,400);
// collide ball with mouse
collide();
// draw ball
ctx.beginPath();
ctx.arc(ball.x, ball.y, ball.r, 0, 6.3);
ctx.fill();
ctx.closePath();
// move
ball.x+=ball.vx;
ball.y+=ball.vy;
// collide with screen
if (ball.x>400) ball.vx=-Math.abs(ball.vx);
if (ball.x<0) ball.vx=Math.abs(ball.vx);
if (ball.y>400) ball.vy=-Math.abs(ball.vy);
if (ball.y<0) ball.vy=Math.abs(ball.vy);
}
animate();
// --- Mouse handling ---
addEventListener('mousemove', mouseMove);
var mx=-1, my=-1, lastmx=-1, lastmy=-1;
var cvRect = cv.getBoundingClientRect();
var cvLeft = cvRect.left;
var cvTop = cvRect.top;
function mouseMove(e) {
lastmx = mx; lastmy=my;
mx=e.clientX - cvLeft;
my=e.clientY - cvTop;
}
function sq(x) { return x*x; }
I want to visualize a huge diagram that is drawn in a HTML5 canvas. As depicted below, let’s imagine the world map, it’s impossible to visualize it all at the same time with a “decent” detail. Therefore, in my canvas I would like to be able to pan over it using the mouse to see the other countries that are not visible.
Does anyone know how to implement this sort of panning in a HTML5 canvas? Another feature would be the zoom in and out.
I've seen a few examples but I couldn't get them working nor they seam to address my question.
Thanks in advance!
To achieve a panning functionality with a peep-hole it's simply a matter of two draw operations, one full and one clipped.
To get this result you can do the following (see full code here):
Setup variables:
var ctx = canvas.getContext('2d'),
ix = 0, iy = 0, /// image position
offsetX = 0, offsetY = 0, /// current offsets
deltaX, deltaY, /// deltas from mouse down
mouseDown = false, /// in mouse drag
img = null, /// background
rect, /// rect position
rectW = 200, rectH = 150; /// size of highlight area
Set up the main functions that you use to set size according to window size (including on resize):
/// calc canvas w/h in relation to window as well as
/// setting rectangle in center with the pre-defined
/// width and height
function setSize() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
rect = [canvas.width * 0.5 - rectW * 0.5,
canvas.height * 0.5 - rectH * 0.5,
rectW, rectH]
update();
}
/// window resize so recalc canvas and rect
window.onresize = setSize;
The main function in this is the draw function. Here we draw the image on the position calculated by mouse moving (see next section).
First step to get that washed-out look is to set alpha down to about 0.2 (you could also draw a transparent rectangle on top but this is more efficient).
Then draw the complete image.
Reset alpha
Draw the peep-hole using clipping with corrected offsets for the source.
-
/// main draw
function update() {
if (img === null) return;
/// limit x/y as drawImage cannot draw with negative
/// offsets for clipping
if (ix + offsetX > rect[0]) ix = rect[0] - offsetX;
if (iy + offsetY > rect[1]) iy = rect[1] - offsetY;
/// clear background to clear off garbage
ctx.clearRect(0, 0, canvas.width, canvas.height);
/// make everything transparent
ctx.globalAlpha = 0.2;
/// draw complete background
ctx.drawImage(img, ix + offsetX, iy + offsetY);
/// reset alpha as we need opacity for next draw
ctx.globalAlpha = 1;
/// draw a clipped version of the background and
/// adjust for offset and image position
ctx.drawImage(img, -ix - offsetX + rect[0], /// sx
-iy - offsetY + rect[1], /// sy
rect[2], rect[3], /// sw/h
/// destination
rect[0], rect[1], rect[2], rect[3]);
/// make a nice sharp border by offsetting it half pixel
ctx.strokeRect(rect[0] + 0.5, rect[1] + 0.5, rect[2], rect[3]);
}
Now it's a matter of handling mouse down, move and up and calculate the offsets -
In the mouse down we store current mouse positions that we'll use for calculating deltas on mouse move:
canvas.onmousedown = function(e) {
/// don't do anything until we have an image
if (img === null) return;
/// correct mouse pos
var coords = getPos(e),
x = coords[0],
y = coords[1];
/// store current position to calc deltas
deltaX = x;
deltaY = y;
/// here we go..
mouseDown = true;
}
Here we use the deltas to avoid image jumping setting the corner to mouse position. The deltas are transferred as offsets to the update function:
canvas.onmousemove = function(e) {
/// in a drag?
if (mouseDown === true) {
var coords = getPos(e),
x = coords[0],
y = coords[1];
/// offset = current - original position
offsetX = x - deltaX;
offsetY = y - deltaY;
/// redraw what we have so far
update();
}
}
And finally on mouse up we make the offsets a permanent part of the image position:
document.onmouseup = function(e) {
/// was in a drag?
if (mouseDown === true) {
/// not any more!!!
mouseDown = false;
/// make image pos. permanent
ix += offsetX;
iy += offsetY;
/// so we need to reset offsets as well
offsetX = offsetY = 0;
}
}
For zooming the canvas I believe this is already answered in this post - you should be able to merge this with the answer given here:
Zoom Canvas to Mouse Cursor
To do something like you have requested, it is just a case of having 2 canvases, each with different z-index. one canvas smaller than the other and position set to the x and y of the mouse.
Then you just display on the small canvas the correct image based on the position of the x and y on the small canvas in relation to the larger canvas.
However your question is asking for a specific solution, which unless someone has done and they are willing to just dump their code, you're going to find it hard to get a complete answer. I hope it goes well though.