如何在 Canvas 中拖动图像/对象? [英] How to drag images / objects within Canvas?
本文介绍了如何在 Canvas 中拖动图像/对象?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
1) 在 Canvas 上，我正在使用 drawSvg (canvg) 绘制 SVG 文件 (awesome_tiger.svg).
1) On Canvas I am drawing SVG file (awesome_tiger.svg) with drawSvg (canvg).
2) 在那个 SVG 文件上，我正在绘制图像*(green1.png and pink.png)*，其坐标来自 JSON.
2) On that SVG file I am plotting images*(green1.png and pink.png)* whose co-ordinates are getting from JSON.
var dataJSON = data || [];
var dataJSON2 = data2 || [];
3) 因此，我可以平移我正在使用 draw1(scaleValue) 绘制的完整绘图.
3) So on I am able to pan complete drawing which I am drawing with draw1(scaleValue).
4) 当我点击 green.png 和 pink.png 时，它们各自的工具提示可以查看在 tooltipFunc 函数中完成的操作.
4) When I click on green.png and pink.png then their respective tooltip is able to view that is done in tooltipFunc function.
5) 我想要做的是，当单击 green.png/pink.png 并拖动它时，我应该只能拖动这些图像而不是 Svg 文件.如果我点击 svg 文件并拖动它，那么正常的平移应该可以工作，默认情况下是有效的.
有人可以帮忙吗?
我的问题的其他参考:" 下面提到的这个主题的内容，我在 stackoverflow 链接上得到了这个.在此帮助下，任何人都可以帮助我解决我的项目需求问题吗?
"Others reference for my problem:" Content of this topic mention below, I got this on stackoverflow link. With the help of this can anyone help me with my project requirement problem?
以下是我的源代码:
JSON 数据:
data = [
{ "id" :["first"],
"x": ["195"],
"y": ["150"],
"tooltiptxt": ["Region 1"]
},
{
"id" :["second"],
"x": ["255"],
"y": ["180"],
"tooltiptxt": ["Region 2"]
},
{
"id" :["third"],
"x": ["200"],
"y": ["240"],
"tooltiptxt": ["Region 3"]
}
];
data2 = [
{ "id" :["first2"],
"x": ["225"],
"y": ["150"],
"tooltiptxt": ["Region 21"]
},
{
"id" :["second2"],
"x": ["275"],
"y": ["180"],
"tooltiptxt": ["Region 22"]
},
{
"id" :["third3"],
"x": ["300"],
"y": ["240"],
"tooltiptxt": ["Region 23"]
}
];
Javascript Code:
var dataJSON = data || [];
var dataJSON2 = data2 || [];
window.onload = function(){
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext('2d');
var tooltip = null,
timer;
//svg file and png files are collected in files.
var files = ["/static/images/awesome_tiger.svg", "/static/images/green1.png", "/static/images/pink.png"],
images = [],
numOfFiles = files.length,
count = numOfFiles;
/// function to load all images in one go
function loadImages() {
/// go through array of file names
for(var i = 0; i < numOfFiles; i++) {
/// create an image element
var img = document.createElement('img');
/// use common loader as we need to count files
img.onload = imageLoaded;
//img.onerror = ... handle errors
img.src = files[i];
/// push image onto array in the same order as file names
images.push(img);
}
}
loadImages();
function imageLoaded(e) {
/// for each successful load we count down
count--;
if (count === 1)
start(); //start when nothing more to count
}
function start() {
context.drawSvg(files[0], 0, 0, 400*scaleValue, 400*scaleValue);
for(var i = 0, pos; pos = dataJSON[i]; i++) {
/// as we know the alpha ball has index 1 we use that here for images
context.drawImage(images[1], pos.x, pos.y, 20/scaleValue, 20/scaleValue);
}
for(var i = 0, pos; pos = dataJSON2[i]; i++) {
context.drawImage(images[2], pos.x, pos.y, 20/scaleValue, 20/scaleValue);
}
}
//Drawing the svg file with drawSvg and images with drawImage(dataJSON and dataJSON2 are JSON through with will get the x an y co-ordinates for those images to draw)
function draw1(scaleValue){
context.save();
context.setTransform(1,0,0,1,0,0)
context.globalAlpha = 0.5;
context.clearRect(0, 0, canvas.width, canvas.height);
context.restore();
context.save();
context.drawSvg(files[0], 0, 0, 400*scaleValue, 400*scaleValue)
context.scale(scaleValue, scaleValue);
for(var i = 0, pos; pos = dataJSON[i]; i++) {
/// as we know the alpha ball has index 1 we use that here for images
context.drawImage(images[1], pos.x, pos.y, 20/scaleValue, 20/scaleValue);
}
for(var i = 0, pos; pos = dataJSON2[i]; i++) {
/// as we know the alpha ball has index 1 we use that here for images
context.drawImage(images[2], pos.x, pos.y, 20/scaleValue, 20/scaleValue);
}
context.restore();
};
//Code for Zoom In and Zoom Out
var scaleValue = 1;
var scaleMultiplier = 0.8;
draw1(scaleValue);
var startDragOffset = {};
var mouseDown = false;
// add button event listeners
document.getElementById("plus").addEventListener("click", function(){
scaleValue /= scaleMultiplier;
draw1(scaleValue);
}, false);
document.getElementById("minus").addEventListener("click", function(){
scaleValue *= scaleMultiplier;
draw1(scaleValue);
}, false);
document.getElementById("original_size").addEventListener("click", function(){
scaleValue = 1;
draw1(scaleValue);
}, false);
//Code for panning on canvas
var isDown = false;
var startCoords = [];
var transX, transY;
var last = [0, 0];
canvas.onmousedown = function(e){
clearTooltip();
isDown = true;
startCoords = [
e.offsetX - last[0],
e.offsetY - last[1]
];
};
canvas.onmouseup = function(e){
isDown = false;
last = [
e.offsetX - startCoords[0], // set last coordinates
e.offsetY - startCoords[1]
];
};
canvas.onmousemove = function(e){
var x = e.offsetX;
var y = e.offsetY;
transX = parseInt(parseInt(x) - parseInt(startCoords[0]));
transY = parseInt(parseInt(y) - parseInt(startCoords[1]));
if(!isDown) return;
context.setTransform(1, 0, 0, 1, transX, transY);
draw1(scaleValue);
}
canvas.addEventListener('click', function(e) {
var x = e.offsetX;
var y = e.offsetY;
transX = parseInt(parseInt(x) - parseInt(startCoords[0]));
transY = parseInt(parseInt(y) - parseInt(startCoords[1]));
tooltipFunc(e, transX, transY);
}, false);
//tooptip function
function tooltipFunc(e, transX, transY){
//document.body.style.cursor = 'default';
var translationX, translationY;
var r = canvas.getBoundingClientRect(),
x = e.clientX - r.left,
y = e.clientY - r.top,
i = 0,
r,
inTooltip = false;
if((typeof startCoords[0] == 'undefined' || startCoords[0] === 'NaN') && (typeof startCoords[1] === 'undefined' || startCoords[1] === 'NaN')){
console.log('if');
for (; r = dataJSON[i]; i++) {
if (x >= parseInt(dataJSON[i].x[0] * scaleValue) + parseInt(scaleValue) && x <= parseInt(dataJSON[i].x[0] * scaleValue) + parseInt(20/scaleValue) && y >= parseInt(dataJSON[i].y[0] * scaleValue) && y <= parseInt(dataJSON[i].y[0] * scaleValue) + parseInt(20/scaleValue)) {
//clearTooltip();
showTooltip(e.clientX, e.clientY, i);
inTooltip = true;
}
}
}
else {
console.log('else');
for (var i = 0; r = dataJSON[i]; i++) {
console.log('else for');
if(x >= parseInt(parseInt(dataJSON[i].x[0] * scaleValue) + parseInt(scaleValue) + parseInt(transX)) && x <= parseInt(parseInt(dataJSON[i].x[0] * scaleValue) + parseInt(scaleValue) + parseInt(transX) + parseInt(20)) && y >= parseInt(parseInt(dataJSON[i].y[0] * scaleValue) + parseInt(scaleValue) + parseInt(transY)) && y <= parseInt(parseInt(dataJSON[i].y[0] * scaleValue) + parseInt(scaleValue) + parseInt(transY) + parseInt(20))) {
clearTooltip();
showTooltip(e.clientX, e.clientY, i);
inTooltip = true;
}
}
for (var i = 0; r = dataJSON2[i]; i++) {
console.log('else for');
if(x >= parseInt(parseInt(dataJSON2[i].x[0] * scaleValue) + parseInt(scaleValue) + parseInt(transX)) && x <= parseInt(parseInt(dataJSON2[i].x[0] * scaleValue) + parseInt(scaleValue) + parseInt(transX) + parseInt(20)) && y >= parseInt(parseInt(dataJSON2[i].y[0] * scaleValue) + parseInt(scaleValue) + parseInt(transY)) && y <= parseInt(parseInt(dataJSON2[i].y[0] * scaleValue) + parseInt(scaleValue) + parseInt(transY) + parseInt(20))) {
clearTooltip();
showTooltip2(e.clientX, e.clientY, i);
inTooltip = true;
}
}
}
}
}
我的问题的其他参考:
<html>
<head>
<title>Test Page</title>
<script type="text/javascript" src="jquery.js"></script>
</head>
<body>
<canvas id="c" width = "500" height = "500" ></canvas>
<script type="text/javascript">
var canvas = $("#c");
var c = canvas[0].getContext("2d");
//var path = "http://wonderfl.net/images/icon/e/ec/ec3c/ec3c37ba9594a7b47f1126b2561efd35df2251bfm";
var path = "blue.jpg";
var path2 = "purple.jpg";
var image1 = new DragImage(path, 200, 100);
var image2 = new DragImage(path2, 300, 100);
var loop = setInterval(function() {
c.fillStyle = "gray";
c.fillRect(0, 0, 500, 500);
image1.update();
image2.update();
}, 30);
var mouseX = 0,
mouseY = 0;
var mousePressed = false;
var dragging = false;
canvas.mousemove(function(e) {
mouseX = e.offsetX;
mouseY = e.offsetY;
})
$(document).mousedown(function() {
mousePressed = true;
}).mouseup(function() {
mousePressed = false;
dragging = false;
});
function DragImage(src, x, y) {
var that = this;
var startX = 0,
startY = 0;
var drag = false;
this.x = x;
this.y = y;
var img = new Image();
img.src = src;
this.update = function() {
if (mousePressed ) {
var left = that.x;
var right = that.x + img.width;
var top = that.y;
var bottom = that.y + img.height;
if (!drag) {
startX = mouseX - that.x;
startY = mouseY - that.y;
}
if (mouseX < right && mouseX > left && mouseY < bottom && mouseY > top) {
if (!dragging){
dragging = true;
drag = true;
}
}
} else {
drag = false;
}
if (drag) {
that.x = mouseX - startX;
that.y = mouseY - startY;
}
c.drawImage(img, that.x, that.y);
}
}
</script>
</body>
</html>
推荐答案
希望我能理解你的问题...！
Hopefully I understand your question...!
以下是平移画布和在画布上拖动对象的方法
这说明了任何拖动或平移之前的画布:
This illustrates the canvas before any dragging or panning:
注意绿色矩形位于老虎的左眼上方.
Notice the green rect is over the tiger's left eye.
这说明了将绿色矩形拖到右眼后的画布:
This illustrates the canvas after the green rect has been dragged to the right eye:
这说明了平移后的画布.
This illustrates the canvas after panning.
老虎和所有矩形都将同时平移.
Both the tiger and all rects will pan simultaneously.
大部分重要代码都在 mousedown 和 mousemove 事件处理程序中
Most of the important code is in the mousedown and mousemove event handlers
鼠标按下时:
- 如果鼠标超过 1 个以上的彩色图像，则拖动图像.
- 如果鼠标未悬停在任何彩色图像上，则平移画布.
这是鼠标按下代码:
function handleMouseDown(e){
// get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// set the starting drag position
// this is needed in mousemove to determine how far we have dragged
lastX=mouseX;
lastY=mouseY;
// test if we're over any of the images
// if yes, put those image(s) in an array called dragging
dragging=imagesHitTests(mouseX,mouseY);
// set the dragging flag
isDown=true;
}
鼠标移动时:
- 确定我们是在拖动还是平移.
- 如果 dragging[] 数组不为空，我们正在拖动.
- 如果 dragging[] 数组为空，我们正在平移.
- 拖动时，根据我们拖动的量更改每个拖动图像的 XY.
- 平移时，根据我们拖动的数量更改老虎的位置.
这是鼠标移动代码:
function handleMouseMove(e){
// if we're not dragging, exit
if(!isDown){return;}
//get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// calc how much the mouse has moved since we were last here
var dx=mouseX-lastX;
var dy=mouseY-lastY;
// set the lastXY for next time we're here
lastX=mouseX;
lastY=mouseY;
// handle drags/pans
if(dragging.length>0){
// we're dragging images
// move all affected images by how much the mouse has moved
for(var i=0;i<dragging.length;i++){
img=images[dragging[i]];
img.x+=dx;
img.y+=dy;
}
}else{
// we're panning the tiger
// set the panXY by how much the mouse has moved
panX+=dx;
panY+=dy;
}
draw();
}
这里的代码用于确定哪些彩色图像位于鼠标下方——并将被拖动.
鼠标下的任何彩色图像都被添加到一个名为拖动"的数组中.
Any color-image under the mouse is added to an array called "dragging".
这个 dragging[] 数组用于 mousemove 来拖动适当的彩色图像.
This dragging[] array is used in mousemove to drag the appropriate color-image(s).
// create an array of any "hit" colored-images
function imagesHitTests(x,y){
// adjust for panning
x-=panX;
y-=panY;
// create var to hold any hits
var hits=[];
// hit-test each image
// add hits to hits[]
for(var i=0;i<images.length;i++){
var img=images[i];
if(x>img.x && x<img.x+img.width && y>img.y && y<img.y+img.height){
hits.push(i);
}
}
return(hits);
}
这是完整的代码和小提琴:http://jsfiddle.net/m1erickson/pbRq2/
Here is complete code and a Fiddle: http://jsfiddle.net/m1erickson/pbRq2/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; padding:20px;}
#canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
ctx.strokeStyle="red";
ctx.lineWidth=5;
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var lastX=0;
var lastY=0;
var panX=0;
var panY=0;
var dragging=[];
var isDown=false;
// create green & pink "images" (we just use rects instead of images)
var images=[];
images.push({x:200,y:150,width:25,height:25,color:"green"});
images.push({x:80,y:235,width:25,height:25,color:"pink"});
// load the tiger image
var tiger=new Image();
tiger.onload=function(){
draw();
}
tiger.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/tiger.png";
function draw(){
ctx.clearRect(0,0,canvas.width,canvas.height);
// draw tiger
ctx.globalAlpha=0.25;
ctx.drawImage(tiger,panX,panY,tiger.width,tiger.height);
// draw color images
ctx.globalAlpha=1.00;
for(var i=0;i<images.length;i++){
var img=images[i];
ctx.beginPath();
ctx.rect(img.x+panX,img.y+panY,img.width,img.height);
ctx.fillStyle=img.color;
ctx.fill();
ctx.stroke();
}
}
// create an array of any "hit" colored-images
function imagesHitTests(x,y){
// adjust for panning
x-=panX;
y-=panY;
// create var to hold any hits
var hits=[];
// hit-test each image
// add hits to hits[]
for(var i=0;i<images.length;i++){
var img=images[i];
if(x>img.x && x<img.x+img.width && y>img.y && y<img.y+img.height){
hits.push(i);
}
}
return(hits);
}
function handleMouseDown(e){
// get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// set the starting drag position
lastX=mouseX;
lastY=mouseY;
// test if we're over any of the images
dragging=imagesHitTests(mouseX,mouseY);
// set the dragging flag
isDown=true;
}
function handleMouseUp(e){
// clear the dragging flag
isDown=false;
}
function handleMouseMove(e){
// if we're not dragging, exit
if(!isDown){return;}
//get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// calc how much the mouse has moved since we were last here
var dx=mouseX-lastX;
var dy=mouseY-lastY;
// set the lastXY for next time we're here
lastX=mouseX;
lastY=mouseY;
// handle drags/pans
if(dragging.length>0){
// we're dragging images
// move all affected images by how much the mouse has moved
for(var i=0;i<dragging.length;i++){
img=images[dragging[i]];
img.x+=dx;
img.y+=dy;
}
}else{
// we're panning the tiger
// set the panXY by how much the mouse has moved
panX+=dx;
panY+=dy;
}
draw();
}
// use jQuery to handle mouse events
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>
这篇关于如何在 Canvas 中拖动图像/对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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