使用光标事件缩放图像的选定部分 [英] zooming a selected part of image with cursor event
本文介绍了使用光标事件缩放图像的选定部分的处理方法，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
我有这个jsfiddle: http://jsfiddle.net/seekpunk/JDU9f/1/
我想要的是当用户进行选择时将选定的部分放大.无论如何，有没有实现这一目标的东西?
这是到目前为止的代码:
var canvas = document.getElementById("MyCanvas");
var ctx = canvas.getContext('2d'),
w = canvas.width,
h = canvas.height,
x1,
y1,
isDown = false;
var img = new Image();
img.src = "http://www.stockfreeimages.com/static/homepage/female-chaffinch-free-stock-photo-106202.jpg";
canvas.onmousedown = function (e) {
var rect = canvas.getBoundingClientRect();
x1 = e.clientX - rect.left;
y1 = e.clientY - rect.top;
isDown = true;
}
canvas.onmouseup = function () {
isDown = false;
}
canvas.onmousemove = function (e) {
if (!isDown) return;
var rect = canvas.getBoundingClientRect(),
x2 = e.clientX - rect.left,
y2 = e.clientY - rect.top;
ctx.clearRect(0, 0, w, h);
ctx.drawImage(img, 0, 0, w, h);
ctx.strokeRect(x1, y1, x2 - x1, y2 - y1);
}
img.onload = function () {
ctx.drawImage(img, 0, 0, w, h);
};
我可以进行选择，但是如何仅缩放所选部分?像这个例子: http://canvasjs.com/docs/charts/basics-of-creating-html5-chart/zooming-panning/
解决方案
对于那些在不使用画布的情况下寻求缩放功能 的人来说，这是一个使用简单的<img />的万无一失的解决方案: /p>
$(window).on("load",function() {
//VARS===================================================
var zoom = {
zoomboxLeft:null, zoomboxTop:null, //zoombox
cursorStartX:null, cursorStartY:null, //cursor
imgStartLeft:null, imgStartTop:null, //image
minDragLeft:null,maxDragLeft:null, minDragTop:null,maxDragTop:null
};
//KEY-HANDLERS===========================================
$(document).keydown(function(e) {
if (e.which==32) {e.preventDefault(); if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").addClass("drag");}} //SPACE
});
$(document).keyup(function(e) {
if (e.which==32) {if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").removeClass("drag");}} //SPACE
});
//RESET IMAGE SIZE=======================================
$(".reset").on("click",function() {
var zoombox = "#"+$(this).parent().attr("id")+" .zoombox";
$(zoombox+" img").css({"left":0, "top":0, "width":$(zoombox).width(), "height":$(zoombox).height()});
}).click();
//ZOOM&DRAG-EVENTS=======================================
//MOUSEDOWN----------------------------------------------
$(".zoombox img").mousedown(function(e) {
e.preventDefault();
$(".zoombox img").addClass("moving");
var selector = $(this).next();
var zoombox = $(this).parent();
$(zoombox).addClass("active");
//store zoombox left&top
zoom.zoomboxLeft = $(zoombox).offset().left + parseInt($(zoombox).css("border-left-width").replace(/\D+/,""));
zoom.zoomboxTop = $(zoombox).offset().top + parseInt($(zoombox).css("border-top-width").replace(/\D+/,""));
//store starting positions of cursor (relative to zoombox)
zoom.cursorStartX = e.pageX - zoom.zoomboxLeft;
zoom.cursorStartY = e.pageY - zoom.zoomboxTop;
if ($(".zoombox img").hasClass("drag")) {
//store starting positions of image (relative to zoombox)
zoom.imgStartLeft = $(this).position().left;
zoom.imgStartTop = $(this).position().top;
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = $(zoombox).width() - $(this).width();
zoom.maxDragLeft = 0;
zoom.minDragTop = $(zoombox).height() - $(this).height();
zoom.maxDragTop = 0;
} else {
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = 0;
zoom.maxDragLeft = $(zoombox).width();
zoom.minDragTop = 0;
zoom.maxDragTop = $(zoombox).height();
//activate zoom-selector
$(selector).css({"display":"block", "width":0, "height":0, "left":zoom.cursorStartX, "top":zoom.cursorStartY});
}
});
//MOUSEMOVE----------------------------------------------
$(document).mousemove(function(e) {
if ($(".zoombox img").hasClass("moving")) {
if ($(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
//update image position (relative to zoombox)
$(img).css({
"left": zoom.imgStartLeft + (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX,
"top": zoom.imgStartTop + (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY
});
//prevent dragging in prohibited areas (relative to zoombox)
if ($(img).position().left <= zoom.minDragLeft) {$(img).css("left",zoom.minDragLeft);} else
if ($(img).position().left >= zoom.maxDragLeft) {$(img).css("left",zoom.maxDragLeft);}
if ($(img).position().top <= zoom.minDragTop) {$(img).css("top",zoom.minDragTop);} else
if ($(img).position().top >= zoom.maxDragTop) {$(img).css("top",zoom.maxDragTop);}
} else {
//calculate selector width and height (relative to zoombox)
var width = (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX;
var height = (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY;
//prevent dragging in prohibited areas (relative to zoombox)
if (e.pageX-zoom.zoomboxLeft <= zoom.minDragLeft) {width = zoom.minDragLeft - zoom.cursorStartX;} else
if (e.pageX-zoom.zoomboxLeft >= zoom.maxDragLeft) {width = zoom.maxDragLeft - zoom.cursorStartX;}
if (e.pageY-zoom.zoomboxTop <= zoom.minDragTop) {height = zoom.minDragTop - zoom.cursorStartY;} else
if (e.pageY-zoom.zoomboxTop >= zoom.maxDragTop) {height = zoom.maxDragTop - zoom.cursorStartY;}
//update zoom-selector
var selector = $(".zoombox.active .selector")[0];
$(selector).css({"width":Math.abs(width), "height":Math.abs(height)});
if (width<0) {$(selector).css("left",zoom.cursorStartX-Math.abs(width));}
if (height<0) {$(selector).css("top",zoom.cursorStartY-Math.abs(height));}
}
}
});
//MOUSEUP------------------------------------------------
$(document).mouseup(function() {
if ($(".zoombox img").hasClass("moving")) {
if (!$(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
var selector = $(".zoombox.active .selector")[0];
if ($(selector).width()>0 && $(selector).height()>0) {
//resize zoom-selector and image
var magnification = ($(selector).width()<$(selector).height() ? $(selector).parent().width()/$(selector).width() : $(selector).parent().height()/$(selector).height()); //go for the highest magnification
var hFactor = $(img).width() / ($(selector).position().left-$(img).position().left);
var vFactor = $(img).height() / ($(selector).position().top-$(img).position().top);
$(selector).css({"width":$(selector).width()*magnification, "height":$(selector).height()*magnification});
$(img).css({"width":$(img).width()*magnification, "height":$(img).height()*magnification});
//correct for misalignment during magnification, caused by size-factor
$(img).css({
"left": $(selector).position().left - ($(img).width()/hFactor),
"top": $(selector).position().top - ($(img).height()/vFactor)
});
//reposition zoom-selector and image (relative to zoombox)
var selectorLeft = ($(selector).parent().width()/2) - ($(selector).width()/2);
var selectorTop = ($(selector).parent().height()/2) - ($(selector).height()/2);
var selectorDeltaLeft = selectorLeft - $(selector).position().left;
var selectorDeltaTop = selectorTop - $(selector).position().top;
$(selector).css({"left":selectorLeft, "top":selectorTop});
$(img).css({"left":"+="+selectorDeltaLeft, "top":"+="+selectorDeltaTop});
}
//deactivate zoom-selector
$(selector).css({"display":"none", "width":0, "height":0, "left":0, "top":0});
} else {$(".zoombox img").removeClass("drag");}
$(".zoombox img").removeClass("moving");
$(".zoombox.active").removeClass("active");
}
});
});
/*CONTAINER-------------------*/
#container {
width: 234px;
height: 199px;
margin-left: auto;
margin-right: auto;
}
/*ZOOMBOX=====================*/
/*IMAGE-----------------------*/
.zoombox {
position:relative;
width: 100%;
height: 100%;
border: 2px solid #AAAAAA;
background-color: #666666;
overflow: hidden;
}
.zoombox img {position:relative;}
.zoombox img.drag {cursor:move;}
.zoombox .selector {
display: none;
position: absolute;
border: 1px solid #999999;
background-color: rgba(255,255,255, 0.3);
}
/*CONTROL---------------------*/
.reset {float:left;}
.info {float:right;}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="container">
<!--ZOOMBOX-->
<div class="zoombox">
<img src="http://www.w3schools.com/colors/img_colormap.gif" />
<div class="selector"></div>
</div>
<input type="button" class="reset" value="Reset" /><span class="info">Press SPACE to drag</span>
</div>
jsfiddle: http://jsfiddle.net/2nt8k8e6/
-
container元素可以是任何内容，只需将.zoombox放在您的网页上，它就可以正常工作. - 您甚至应该可以将多个
.zoombox放在同一容器元素中并排放置.我还没有测试过.
并不太复杂，没有很多注释，但是变量名非常不言自明，使代码易于阅读，并且可以查找所有jquery函数.
该代码本质上分为三个处理程序:.mousedown()，.mousemove()，.mouseup().
-在mousedown中，某些值存储在变量中(例如选择器的起始坐标)，这些变量在mousemove和mouseup中用作参考.
如果您想确切了解正在发生的事情，请看一下代码，正如我所说的那样，并不太困难.
I have this jsfiddle : http://jsfiddle.net/seekpunk/JDU9f/1/
what I want is when the user do a selection the selected part is zoomed in .Is there anyway to achieve this ?
this is the code so far :
var canvas = document.getElementById("MyCanvas");
var ctx = canvas.getContext('2d'),
w = canvas.width,
h = canvas.height,
x1,
y1,
isDown = false;
var img = new Image();
img.src = "http://www.stockfreeimages.com/static/homepage/female-chaffinch-free-stock-photo-106202.jpg";
canvas.onmousedown = function (e) {
var rect = canvas.getBoundingClientRect();
x1 = e.clientX - rect.left;
y1 = e.clientY - rect.top;
isDown = true;
}
canvas.onmouseup = function () {
isDown = false;
}
canvas.onmousemove = function (e) {
if (!isDown) return;
var rect = canvas.getBoundingClientRect(),
x2 = e.clientX - rect.left,
y2 = e.clientY - rect.top;
ctx.clearRect(0, 0, w, h);
ctx.drawImage(img, 0, 0, w, h);
ctx.strokeRect(x1, y1, x2 - x1, y2 - y1);
}
img.onload = function () {
ctx.drawImage(img, 0, 0, w, h);
};
I can make the selection but how can i zoom the selected part only ? like this example : http://canvasjs.com/docs/charts/basics-of-creating-html5-chart/zooming-panning/
解决方案
For those looking for zooming functionality without the use of a canvas, here's a pretty foolproof solution using a simple <img />:
$(window).on("load",function() {
//VARS===================================================
var zoom = {
zoomboxLeft:null, zoomboxTop:null, //zoombox
cursorStartX:null, cursorStartY:null, //cursor
imgStartLeft:null, imgStartTop:null, //image
minDragLeft:null,maxDragLeft:null, minDragTop:null,maxDragTop:null
};
//KEY-HANDLERS===========================================
$(document).keydown(function(e) {
if (e.which==32) {e.preventDefault(); if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").addClass("drag");}} //SPACE
});
$(document).keyup(function(e) {
if (e.which==32) {if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").removeClass("drag");}} //SPACE
});
//RESET IMAGE SIZE=======================================
$(".reset").on("click",function() {
var zoombox = "#"+$(this).parent().attr("id")+" .zoombox";
$(zoombox+" img").css({"left":0, "top":0, "width":$(zoombox).width(), "height":$(zoombox).height()});
}).click();
//ZOOM&DRAG-EVENTS=======================================
//MOUSEDOWN----------------------------------------------
$(".zoombox img").mousedown(function(e) {
e.preventDefault();
$(".zoombox img").addClass("moving");
var selector = $(this).next();
var zoombox = $(this).parent();
$(zoombox).addClass("active");
//store zoombox left&top
zoom.zoomboxLeft = $(zoombox).offset().left + parseInt($(zoombox).css("border-left-width").replace(/\D+/,""));
zoom.zoomboxTop = $(zoombox).offset().top + parseInt($(zoombox).css("border-top-width").replace(/\D+/,""));
//store starting positions of cursor (relative to zoombox)
zoom.cursorStartX = e.pageX - zoom.zoomboxLeft;
zoom.cursorStartY = e.pageY - zoom.zoomboxTop;
if ($(".zoombox img").hasClass("drag")) {
//store starting positions of image (relative to zoombox)
zoom.imgStartLeft = $(this).position().left;
zoom.imgStartTop = $(this).position().top;
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = $(zoombox).width() - $(this).width();
zoom.maxDragLeft = 0;
zoom.minDragTop = $(zoombox).height() - $(this).height();
zoom.maxDragTop = 0;
} else {
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = 0;
zoom.maxDragLeft = $(zoombox).width();
zoom.minDragTop = 0;
zoom.maxDragTop = $(zoombox).height();
//activate zoom-selector
$(selector).css({"display":"block", "width":0, "height":0, "left":zoom.cursorStartX, "top":zoom.cursorStartY});
}
});
//MOUSEMOVE----------------------------------------------
$(document).mousemove(function(e) {
if ($(".zoombox img").hasClass("moving")) {
if ($(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
//update image position (relative to zoombox)
$(img).css({
"left": zoom.imgStartLeft + (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX,
"top": zoom.imgStartTop + (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY
});
//prevent dragging in prohibited areas (relative to zoombox)
if ($(img).position().left <= zoom.minDragLeft) {$(img).css("left",zoom.minDragLeft);} else
if ($(img).position().left >= zoom.maxDragLeft) {$(img).css("left",zoom.maxDragLeft);}
if ($(img).position().top <= zoom.minDragTop) {$(img).css("top",zoom.minDragTop);} else
if ($(img).position().top >= zoom.maxDragTop) {$(img).css("top",zoom.maxDragTop);}
} else {
//calculate selector width and height (relative to zoombox)
var width = (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX;
var height = (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY;
//prevent dragging in prohibited areas (relative to zoombox)
if (e.pageX-zoom.zoomboxLeft <= zoom.minDragLeft) {width = zoom.minDragLeft - zoom.cursorStartX;} else
if (e.pageX-zoom.zoomboxLeft >= zoom.maxDragLeft) {width = zoom.maxDragLeft - zoom.cursorStartX;}
if (e.pageY-zoom.zoomboxTop <= zoom.minDragTop) {height = zoom.minDragTop - zoom.cursorStartY;} else
if (e.pageY-zoom.zoomboxTop >= zoom.maxDragTop) {height = zoom.maxDragTop - zoom.cursorStartY;}
//update zoom-selector
var selector = $(".zoombox.active .selector")[0];
$(selector).css({"width":Math.abs(width), "height":Math.abs(height)});
if (width<0) {$(selector).css("left",zoom.cursorStartX-Math.abs(width));}
if (height<0) {$(selector).css("top",zoom.cursorStartY-Math.abs(height));}
}
}
});
//MOUSEUP------------------------------------------------
$(document).mouseup(function() {
if ($(".zoombox img").hasClass("moving")) {
if (!$(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
var selector = $(".zoombox.active .selector")[0];
if ($(selector).width()>0 && $(selector).height()>0) {
//resize zoom-selector and image
var magnification = ($(selector).width()<$(selector).height() ? $(selector).parent().width()/$(selector).width() : $(selector).parent().height()/$(selector).height()); //go for the highest magnification
var hFactor = $(img).width() / ($(selector).position().left-$(img).position().left);
var vFactor = $(img).height() / ($(selector).position().top-$(img).position().top);
$(selector).css({"width":$(selector).width()*magnification, "height":$(selector).height()*magnification});
$(img).css({"width":$(img).width()*magnification, "height":$(img).height()*magnification});
//correct for misalignment during magnification, caused by size-factor
$(img).css({
"left": $(selector).position().left - ($(img).width()/hFactor),
"top": $(selector).position().top - ($(img).height()/vFactor)
});
//reposition zoom-selector and image (relative to zoombox)
var selectorLeft = ($(selector).parent().width()/2) - ($(selector).width()/2);
var selectorTop = ($(selector).parent().height()/2) - ($(selector).height()/2);
var selectorDeltaLeft = selectorLeft - $(selector).position().left;
var selectorDeltaTop = selectorTop - $(selector).position().top;
$(selector).css({"left":selectorLeft, "top":selectorTop});
$(img).css({"left":"+="+selectorDeltaLeft, "top":"+="+selectorDeltaTop});
}
//deactivate zoom-selector
$(selector).css({"display":"none", "width":0, "height":0, "left":0, "top":0});
} else {$(".zoombox img").removeClass("drag");}
$(".zoombox img").removeClass("moving");
$(".zoombox.active").removeClass("active");
}
});
});
/*CONTAINER-------------------*/
#container {
width: 234px;
height: 199px;
margin-left: auto;
margin-right: auto;
}
/*ZOOMBOX=====================*/
/*IMAGE-----------------------*/
.zoombox {
position:relative;
width: 100%;
height: 100%;
border: 2px solid #AAAAAA;
background-color: #666666;
overflow: hidden;
}
.zoombox img {position:relative;}
.zoombox img.drag {cursor:move;}
.zoombox .selector {
display: none;
position: absolute;
border: 1px solid #999999;
background-color: rgba(255,255,255, 0.3);
}
/*CONTROL---------------------*/
.reset {float:left;}
.info {float:right;}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="container">
<!--ZOOMBOX-->
<div class="zoombox">
<img src="http://www.w3schools.com/colors/img_colormap.gif" />
<div class="selector"></div>
</div>
<input type="button" class="reset" value="Reset" /><span class="info">Press SPACE to drag</span>
</div>
jsfiddle: http://jsfiddle.net/2nt8k8e6/
- The
containerelement can be anything, just place the.zoomboxon your webpage and it should work. - You should even be able to put multiple
.zoomboxes next to each other in the same container-element. I haven't tested it though.
It's not too complicated, there's not a whole lot of comments, but the variable names are pretty self-explanatory and make the code easy enough to read, and all the jquery-functions can be looked up.
The code is essentially divided into three handlers: .mousedown(), .mousemove(), .mouseup().
- In mousedown some values are stored into variables (like the start-coordinates for the selector), which are used in mousemove and mouseup as a reference.
If you want to know exactly what's happening, just have a look at the code, as I said it's not too difficult.
这篇关于使用光标事件缩放图像的选定部分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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