Javascript 通过HTML5画布上下文缩放并在给定图像上绘制网格
使用HTML5元素,我想加载一个图像文件(PNG、JPEG等),将其绘制到画布上,然后在图像顶部绘制一个网格 另外,我正在尝试为矩形设置一个矩形边距和一个完全透明的内容 我试图修改的示例可以找到 在我的小提琴上Javascript 通过HTML5画布上下文缩放并在给定图像上绘制网格,javascript,html,canvas,Javascript,Html,Canvas,使用HTML5元素,我想加载一个图像文件(PNG、JPEG等),将其绘制到画布上,然后在图像顶部绘制一个网格 另外,我正在尝试为矩形设置一个矩形边距和一个完全透明的内容 我试图修改的示例可以找到 在我的小提琴上 通过HTML5画布上下文缩放 正文{背景:#eee;边距:1em;文本对齐:居中;} 画布{显示:块;边距:1em自动;背景:#fff;边框:1px实心#ccc} 展示如何在HTML5画布上下文上使用转换方法来选择性地放大和缩小。拖动以平移。单击以在该位置缩放。按住Shift键并单击以
通过HTML5画布上下文缩放
正文{背景:#eee;边距:1em;文本对齐:居中;}
画布{显示:块;边距:1em自动;背景:#fff;边框:1px实心#ccc}
展示如何在HTML5画布上下文上使用转换方法来选择性地放大和缩小。拖动以平移。单击以在该位置缩放。按住Shift键并单击以缩小。在画布上向上/向下滑动鼠标滚轮,以放大/缩小该位置
通过以不同比例重新绘制画布,在缩放过程中笔划保持平滑。例如,放大耳环或前额上的圆圈以查看细节
对于(var i=0;iso),我设法编写了以下代码:
<!DOCTYPE html>
<!-- saved from url=(0048)http://phrogz.net/tmp/canvas_zoom_to_cursor.html -->
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Zooming via HTML5 Canvas Context</title>
</head><body style="-webkit-user-select: none;">
<canvas width="800" height="600"></canvas>
<script type="text/javascript" charset="utf-8">
var canvas = document.getElementsByTagName('canvas')[0];
canvas.width = 800; canvas.height = 600;
var gkhead = new Image;
var ball = new Image;
var square_size = 10;
window.onload = function(){
var ctx = canvas.getContext('2d');
trackTransforms(ctx);
function redraw(){
// Clear the entire canvas
var p1 = ctx.transformedPoint(0,0);
var p2 = ctx.transformedPoint(canvas.width,canvas.height);
ctx.clearRect(p1.x,p1.y,p2.x-p1.x,p2.y-p1.y);
ctx.drawImage(gkhead,50,50);//punct stanga sus imagine cu marton
//console.log(ctx);
color='ff0000';
w = gkhead.width;
//console.log(w);
h = gkhead.height;
//console.log(h);
var i = 0;
i = i + 1;
if(i==1)color='ff0000';
if(i==2)color='00ff00';
if(i==3){
color='0000ff';
i=0;
}
ctx.beginPath();
ctx.rect(50,50,gkhead.width,gkhead.height);
ctx.lineWidth = 1;
ctx.strokeStyle = "#" + color;
ctx.stroke();
var ind = 0;
for(var j = 0; j < gkhead.width - square_size; j = j + square_size){
ind++;
ctx.beginPath();
ctx.lineWidth = 1;
ctx.strokeStyle = 'black';
ctx.moveTo(50 + ( ind * square_size ), 50);
ctx.lineTo(50 + ( ind * square_size ), 50 + gkhead.height);
ctx.stroke();
}
var ind = 0;
for(var j = 0; j < gkhead.height - square_size; j = j + square_size){
ind++;
ctx.beginPath();
ctx.lineWidth = 1;
ctx.strokeStyle = 'black';
ctx.moveTo(50, 50 + ( ind * square_size ));
ctx.lineTo(50 + gkhead.width,50 + ( ind * square_size ));
ctx.stroke();
}
ctx.save();
ctx.translate(438.5,223);
ctx.strokeStyle = '#06c';
ctx.beginPath();
ctx.lineWidth = 0.05;
for (var i=0;i<60;++i){
ctx.rotate(6*i*Math.PI/180);
ctx.moveTo(9,0);
ctx.lineTo(10,0);
ctx.rotate(-6*i*Math.PI/180);
}
ctx.stroke();
ctx.restore();
}
redraw();
var lastX=canvas.width/2, lastY=canvas.height/2;
var dragStart,dragged;
canvas.addEventListener('mousedown',function(evt){
document.body.style.mozUserSelect = document.body.style.webkitUserSelect = document.body.style.userSelect = 'none';
lastX = evt.offsetX || (evt.pageX - canvas.offsetLeft);
lastY = evt.offsetY || (evt.pageY - canvas.offsetTop);
console.log(lastX + ' ' + lastY);
dragStart = ctx.transformedPoint(lastX,lastY);
dragged = false;
},false);
canvas.addEventListener('mousemove',function(evt){
lastX = evt.offsetX || (evt.pageX - canvas.offsetLeft);
lastY = evt.offsetY || (evt.pageY - canvas.offsetTop);
dragged = true;
if (dragStart){
var pt = ctx.transformedPoint(lastX,lastY);
ctx.translate(pt.x-dragStart.x,pt.y-dragStart.y);
redraw();
}
},false);
canvas.addEventListener('mouseup',function(evt){
dragStart = null;
if (!dragged) zoom(evt.shiftKey ? -1 : 1 );
},false);
var scaleFactor = 1.1;
var zoom = function(clicks){
var pt = ctx.transformedPoint(lastX,lastY);
ctx.translate(pt.x,pt.y);
var factor = Math.pow(scaleFactor,clicks);
ctx.scale(factor,factor);
ctx.translate(-pt.x,-pt.y);
redraw();
}
var handleScroll = function(evt){
var delta = evt.wheelDelta ? evt.wheelDelta/40 : evt.detail ? -evt.detail : 0;
if (delta) zoom(delta);
return evt.preventDefault() && false;
};
canvas.addEventListener('DOMMouseScroll',handleScroll,false);
canvas.addEventListener('mousewheel',handleScroll,false);
};
gkhead.src = 'http://www.william.ro/wp-content/uploads/2013/07/13.jpg';
//console.log(gkhead.width);
//console.log(gkhead);//img src
ball.src = 'http://phrogz.net/tmp/alphaball.png';
//console.log(ball);
// Adds ctx.getTransform() - returns an SVGMatrix
// Adds ctx.transformedPoint(x,y) - returns an SVGPoint
function trackTransforms(ctx){
var svg = document.createElementNS("http://www.w3.org/2000/svg",'svg');
var xform = svg.createSVGMatrix();
ctx.getTransform = function(){ return xform; };
var savedTransforms = [];
var save = ctx.save;
ctx.save = function(){
savedTransforms.push(xform.translate(0,0));
return save.call(ctx);
};
var restore = ctx.restore;
ctx.restore = function(){
xform = savedTransforms.pop();
return restore.call(ctx);
};
var scale = ctx.scale;
ctx.scale = function(sx,sy){
xform = xform.scaleNonUniform(sx,sy);
return scale.call(ctx,sx,sy);
};
var rotate = ctx.rotate;
ctx.rotate = function(radians){
xform = xform.rotate(radians*180/Math.PI);
return rotate.call(ctx,radians);
};
var translate = ctx.translate;
ctx.translate = function(dx,dy){
xform = xform.translate(dx,dy);
return translate.call(ctx,dx,dy);
};
var transform = ctx.transform;
ctx.transform = function(a,b,c,d,e,f){
var m2 = svg.createSVGMatrix();
m2.a=a; m2.b=b; m2.c=c; m2.d=d; m2.e=e; m2.f=f;
xform = xform.multiply(m2);
return transform.call(ctx,a,b,c,d,e,f);
};
var setTransform = ctx.setTransform;
ctx.setTransform = function(a,b,c,d,e,f){
xform.a = a;
xform.b = b;
xform.c = c;
xform.d = d;
xform.e = e;
xform.f = f;
return setTransform.call(ctx,a,b,c,d,e,f);
};
var pt = svg.createSVGPoint();
ctx.transformedPoint = function(x,y){
pt.x=x; pt.y=y;
return pt.matrixTransform(xform.inverse());
}
}
</script>
</body>
</html>
通过HTML5画布上下文缩放
var canvas=document.getElementsByTagName('canvas')[0];
canvas.width=800;canvas.height=600;
var gkhead=新图像;
var-ball=新图像;
var平方_大小=10;
window.onload=函数(){
var ctx=canvas.getContext('2d');
轨道变换(ctx);
函数重画(){
//清除整个画布
var p1=ctx.转换点(0,0);
var p2=ctx.transformedPoint(canvas.width、canvas.height);
clearRect(p1.x,p1.y,p2.x-p1.x,p2.y-p1.y);
ctx.drawImage(gkhead,50,50);//点状节
//控制台日志(ctx);
颜色='ff0000';
w=gk头宽;
//控制台日志(w);
h=GK头高度;
//控制台日志(h);
var i=0;
i=i+1;
如果(i==1)color='ff0000';
如果(i==2)color='00ff00';
如果(i==3){
颜色='0000ff';
i=0;
}
ctx.beginPath();
ctx.rect(50,50,gkhead.width,gkhead.height);
ctx.lineWidth=1;
ctx.strokeStyle=“#”+颜色;
ctx.stroke();
var-ind=0;
对于(变量j=0;j 对于(var i=0;我能给你发一张你到目前为止所做的事情的小册子吗?告诉我阻止你的是什么问题?
<!DOCTYPE html>
<!-- saved from url=(0048)http://phrogz.net/tmp/canvas_zoom_to_cursor.html -->
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Zooming via HTML5 Canvas Context</title>
</head><body style="-webkit-user-select: none;">
<canvas width="800" height="600"></canvas>
<script type="text/javascript" charset="utf-8">
var canvas = document.getElementsByTagName('canvas')[0];
canvas.width = 800; canvas.height = 600;
var gkhead = new Image;
var ball = new Image;
var square_size = 10;
window.onload = function(){
var ctx = canvas.getContext('2d');
trackTransforms(ctx);
function redraw(){
// Clear the entire canvas
var p1 = ctx.transformedPoint(0,0);
var p2 = ctx.transformedPoint(canvas.width,canvas.height);
ctx.clearRect(p1.x,p1.y,p2.x-p1.x,p2.y-p1.y);
ctx.drawImage(gkhead,50,50);//punct stanga sus imagine cu marton
//console.log(ctx);
color='ff0000';
w = gkhead.width;
//console.log(w);
h = gkhead.height;
//console.log(h);
var i = 0;
i = i + 1;
if(i==1)color='ff0000';
if(i==2)color='00ff00';
if(i==3){
color='0000ff';
i=0;
}
ctx.beginPath();
ctx.rect(50,50,gkhead.width,gkhead.height);
ctx.lineWidth = 1;
ctx.strokeStyle = "#" + color;
ctx.stroke();
var ind = 0;
for(var j = 0; j < gkhead.width - square_size; j = j + square_size){
ind++;
ctx.beginPath();
ctx.lineWidth = 1;
ctx.strokeStyle = 'black';
ctx.moveTo(50 + ( ind * square_size ), 50);
ctx.lineTo(50 + ( ind * square_size ), 50 + gkhead.height);
ctx.stroke();
}
var ind = 0;
for(var j = 0; j < gkhead.height - square_size; j = j + square_size){
ind++;
ctx.beginPath();
ctx.lineWidth = 1;
ctx.strokeStyle = 'black';
ctx.moveTo(50, 50 + ( ind * square_size ));
ctx.lineTo(50 + gkhead.width,50 + ( ind * square_size ));
ctx.stroke();
}
ctx.save();
ctx.translate(438.5,223);
ctx.strokeStyle = '#06c';
ctx.beginPath();
ctx.lineWidth = 0.05;
for (var i=0;i<60;++i){
ctx.rotate(6*i*Math.PI/180);
ctx.moveTo(9,0);
ctx.lineTo(10,0);
ctx.rotate(-6*i*Math.PI/180);
}
ctx.stroke();
ctx.restore();
}
redraw();
var lastX=canvas.width/2, lastY=canvas.height/2;
var dragStart,dragged;
canvas.addEventListener('mousedown',function(evt){
document.body.style.mozUserSelect = document.body.style.webkitUserSelect = document.body.style.userSelect = 'none';
lastX = evt.offsetX || (evt.pageX - canvas.offsetLeft);
lastY = evt.offsetY || (evt.pageY - canvas.offsetTop);
console.log(lastX + ' ' + lastY);
dragStart = ctx.transformedPoint(lastX,lastY);
dragged = false;
},false);
canvas.addEventListener('mousemove',function(evt){
lastX = evt.offsetX || (evt.pageX - canvas.offsetLeft);
lastY = evt.offsetY || (evt.pageY - canvas.offsetTop);
dragged = true;
if (dragStart){
var pt = ctx.transformedPoint(lastX,lastY);
ctx.translate(pt.x-dragStart.x,pt.y-dragStart.y);
redraw();
}
},false);
canvas.addEventListener('mouseup',function(evt){
dragStart = null;
if (!dragged) zoom(evt.shiftKey ? -1 : 1 );
},false);
var scaleFactor = 1.1;
var zoom = function(clicks){
var pt = ctx.transformedPoint(lastX,lastY);
ctx.translate(pt.x,pt.y);
var factor = Math.pow(scaleFactor,clicks);
ctx.scale(factor,factor);
ctx.translate(-pt.x,-pt.y);
redraw();
}
var handleScroll = function(evt){
var delta = evt.wheelDelta ? evt.wheelDelta/40 : evt.detail ? -evt.detail : 0;
if (delta) zoom(delta);
return evt.preventDefault() && false;
};
canvas.addEventListener('DOMMouseScroll',handleScroll,false);
canvas.addEventListener('mousewheel',handleScroll,false);
};
gkhead.src = 'http://www.william.ro/wp-content/uploads/2013/07/13.jpg';
//console.log(gkhead.width);
//console.log(gkhead);//img src
ball.src = 'http://phrogz.net/tmp/alphaball.png';
//console.log(ball);
// Adds ctx.getTransform() - returns an SVGMatrix
// Adds ctx.transformedPoint(x,y) - returns an SVGPoint
function trackTransforms(ctx){
var svg = document.createElementNS("http://www.w3.org/2000/svg",'svg');
var xform = svg.createSVGMatrix();
ctx.getTransform = function(){ return xform; };
var savedTransforms = [];
var save = ctx.save;
ctx.save = function(){
savedTransforms.push(xform.translate(0,0));
return save.call(ctx);
};
var restore = ctx.restore;
ctx.restore = function(){
xform = savedTransforms.pop();
return restore.call(ctx);
};
var scale = ctx.scale;
ctx.scale = function(sx,sy){
xform = xform.scaleNonUniform(sx,sy);
return scale.call(ctx,sx,sy);
};
var rotate = ctx.rotate;
ctx.rotate = function(radians){
xform = xform.rotate(radians*180/Math.PI);
return rotate.call(ctx,radians);
};
var translate = ctx.translate;
ctx.translate = function(dx,dy){
xform = xform.translate(dx,dy);
return translate.call(ctx,dx,dy);
};
var transform = ctx.transform;
ctx.transform = function(a,b,c,d,e,f){
var m2 = svg.createSVGMatrix();
m2.a=a; m2.b=b; m2.c=c; m2.d=d; m2.e=e; m2.f=f;
xform = xform.multiply(m2);
return transform.call(ctx,a,b,c,d,e,f);
};
var setTransform = ctx.setTransform;
ctx.setTransform = function(a,b,c,d,e,f){
xform.a = a;
xform.b = b;
xform.c = c;
xform.d = d;
xform.e = e;
xform.f = f;
return setTransform.call(ctx,a,b,c,d,e,f);
};
var pt = svg.createSVGPoint();
ctx.transformedPoint = function(x,y){
pt.x=x; pt.y=y;
return pt.matrixTransform(xform.inverse());
}
}
</script>
</body>
</html>
var canvas=document.getElementsByTagName('canvas')[0];
画布宽度=800;帆布高度=600;
var gkhead=新图像;
var-ball=新图像;
window.onload=函数(){
var ctx=canvas.getContext('2d');
轨道变换(ctx);
函数重画(){
//清除整个画布
var p1=ctx.转换点(0,0);
var p2=ctx.transformedPoint(canvas.width、canvas.height);
clearRect(p1.x,p1.y,p2.x-p1.x,p2.y-p1.y);
//或者:
//ctx.save();
//setTransform(1,0,0,1,0,0);
//clearRect(0,0,canvas.width,canvas.height);
//ctx.restore();
ctx.drawImage(gkhead,50,50);//点状节
控制台日志(ctx);
ctx.fillStyle=“#FF0000”;
ctx.fillRect(50,50,60,60);
ctx.beginPath();
ctx.lineWidth=10;//rama 10
ctx.moveTo(399250);
ctx.lineTo(474256);
ctx.stroke();
ctx.save();
ctx.translate(4,2);
ctx.beginPath();
ctx.lineWidth=1;//rama 1
ctx.moveTo(436253);
ctx.lineTo(437.5233);
ctx.stroke();
ctx.save();
ctx.translate(438.5223);
ctx.strokeStyle='#06c';
ctx.beginPath();
ctx.lineWidth=0.05;