在 html5 画布上拖动和调整图像大小

Question

I am building a HTML5 canvas image editor.我正在构建一个 HTML5 画布图像编辑器。 After uploading an image in to the canvas i need to Dragg and resize it over the canvas.将图像上传到画布后，我需要在画布上拖动并调整其大小。 I managed to upload an image and make it draggable on the canvas.我设法上传了一张图片并使其可在画布上拖动。 But i need to make it resizable also along the canvas.但我还需要让它沿着画布调整大小。 Thanks in advance.提前致谢。

var Img = new Image();
Img.src = file;
Img.onload = function () {
  context.drawImage(Img, 50, 0, 200, 200); 
}
mouseMove = function (event){
if (down) 
{
 context.clearRect(0,0,800,500);
 context.translate(0, -50); 
 context.drawImage(Img, (event.clientX - offsetX),
 (event.clientY - offsetY), 200, 200);
 context.translate(0, 50);
}
}
mouseUp = function () {
  down = false;
}
mouseDown = function () {
  down = true;
}
canvas.addEventListener('mousedown', mouseDown, false);
canvas.addEventListener('mouseup', mouseUp, false);
canvas.addEventListener('mousemove',mouseMove, false);

I tried with kinetics js but it is not suitable with canvas.我尝试过 kinetics js，但它不适合画布。

Answer 1

Here's example code to allow you to drag and resize an image using Canvas.这是允许您使用 Canvas 拖动和调整图像大小的示例代码。

Resizing调整大小

在此处输入图片说明

How to resize an image with 4 draggable anchors如何使用 4 个可拖动锚点调整图像大小

Draw a draggable anchor on each corner of an image.在图像的每个角上绘制一个可拖动的锚点。
If the user mousedown's one if the anchors, start dragging that anchor.如果用户鼠标按下的是锚点，则开始拖动该锚点。
In the mousemove handler, resize the image using the dragging anchor's position(Note below).在 mousemove 处理程序中，使用拖动锚点的位置调整图像大小（下面的注释）。
As the last act in mousemove, redraw the resized image and 4 new anchors.作为 mousemove 的最后一步，重新绘制调整大小的图像和 4 个新锚点。
On mouseup, stop the anchor's drag.在鼠标悬停时，停止锚点的拖动。

Note on the math used to resize the image:注意用于调整图像大小的数学：

The resized width is the difference between the mouseX position and the opposite corner's X.调整后的宽度是 mouseX 位置和对角 X 之间的差值。
The resized height is the difference between the mouseY position and the opposite corner's Y.调整后的高度是 mouseY 位置和对角 Y 之间的差值。

Dragging拖动

在此处输入图片说明

How to drag an image如何拖动图像

If the user mousedown's inside the image, save the mouses starting XY to begin dragging.如果用户在图像内按下鼠标，则保存从 XY 开始的鼠标以开始拖动。
In the mousemove handler, move the image by the current mouseXY minus the startingXY.在 mousemove 处理程序中，按当前鼠标 XY 减去起始 XY 移动图像。
Also in mousemove, reset the startingXY to the current mouseXY in preparation for continued dragging.同样在 mousemove 中，将起始 XY 重置为当前鼠标 XY 以准备继续拖动。
On mouseup, stop the image's drag.在鼠标悬停时，停止拖动图像。

Here is code and a Fiddle: http://jsfiddle.net/m1erickson/LAS8L/这是代码和小提琴： http : //jsfiddle.net/m1erickson/LAS8L/

<!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:10px;}
    #canvas{border:1px solid red;}
</style>
    
<script>
$(function(){

    var canvas=document.getElementById("canvas");
    var ctx=canvas.getContext("2d");

    var canvasOffset=$("#canvas").offset();
    var offsetX=canvasOffset.left;
    var offsetY=canvasOffset.top;

    var startX;
    var startY;
    var isDown=false;


    var pi2=Math.PI*2;
    var resizerRadius=8;
    var rr=resizerRadius*resizerRadius;
    var draggingResizer={x:0,y:0};
    var imageX=50;
    var imageY=50;
    var imageWidth,imageHeight,imageRight,imageBottom;
    var draggingImage=false;
    var startX;
    var startY;


   
    var img=new Image();
    img.onload=function(){
        imageWidth=img.width;
        imageHeight=img.height;
        imageRight=imageX+imageWidth;
        imageBottom=imageY+imageHeight
        draw(true,false);
    }
    img.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/facesSmall.png";


    function draw(withAnchors,withBorders){

        // clear the canvas
        ctx.clearRect(0,0,canvas.width,canvas.height);

        // draw the image
        ctx.drawImage(img,0,0,img.width,img.height,imageX,imageY,imageWidth,imageHeight);

        // optionally draw the draggable anchors
        if(withAnchors){
            drawDragAnchor(imageX,imageY);
            drawDragAnchor(imageRight,imageY);
            drawDragAnchor(imageRight,imageBottom);
            drawDragAnchor(imageX,imageBottom);
        }
        
        // optionally draw the connecting anchor lines
        if(withBorders){
            ctx.beginPath();
            ctx.moveTo(imageX,imageY);
            ctx.lineTo(imageRight,imageY);
            ctx.lineTo(imageRight,imageBottom);
            ctx.lineTo(imageX,imageBottom);
            ctx.closePath();
            ctx.stroke();
        }

    }

    function drawDragAnchor(x,y){
        ctx.beginPath();
        ctx.arc(x,y,resizerRadius,0,pi2,false);
        ctx.closePath();
        ctx.fill();
    }

    function anchorHitTest(x,y){

        var dx,dy;

        // top-left
        dx=x-imageX;
        dy=y-imageY;
        if(dx*dx+dy*dy<=rr){ return(0); }
        // top-right
        dx=x-imageRight;
        dy=y-imageY;
        if(dx*dx+dy*dy<=rr){ return(1); }
        // bottom-right
        dx=x-imageRight;
        dy=y-imageBottom;
        if(dx*dx+dy*dy<=rr){ return(2); }
        // bottom-left
        dx=x-imageX;
        dy=y-imageBottom;
        if(dx*dx+dy*dy<=rr){ return(3); }
        return(-1);

    }


    function hitImage(x,y){
        return(x>imageX && x<imageX+imageWidth && y>imageY && y<imageY+imageHeight);
    }


    function handleMouseDown(e){
      startX=parseInt(e.clientX-offsetX);
      startY=parseInt(e.clientY-offsetY);
      draggingResizer=anchorHitTest(startX,startY);
      draggingImage= draggingResizer<0 && hitImage(startX,startY);
    }

    function handleMouseUp(e){
      draggingResizer=-1;
      draggingImage=false;
      draw(true,false);
    }

    function handleMouseOut(e){
      handleMouseUp(e);
    }

    function handleMouseMove(e){
      
      if(draggingResizer>-1){
      
          mouseX=parseInt(e.clientX-offsetX);
          mouseY=parseInt(e.clientY-offsetY);

          // resize the image
          switch(draggingResizer){
              case 0: //top-left
                  imageX=mouseX;
                  imageWidth=imageRight-mouseX;
                  imageY=mouseY;
                  imageHeight=imageBottom-mouseY;
                  break;
              case 1: //top-right
                  imageY=mouseY;
                  imageWidth=mouseX-imageX;
                  imageHeight=imageBottom-mouseY;
                  break;
              case 2: //bottom-right
                  imageWidth=mouseX-imageX;
                  imageHeight=mouseY-imageY;
                  break;
              case 3: //bottom-left
                  imageX=mouseX;
                  imageWidth=imageRight-mouseX;
                  imageHeight=mouseY-imageY;
                  break;
          }

          // enforce minimum dimensions of 25x25
          if(imageWidth<25){imageWidth=25;}
          if(imageHeight<25){imageHeight=25;}

          // set the image right and bottom
          imageRight=imageX+imageWidth;
          imageBottom=imageY+imageHeight;
          
          // redraw the image with resizing anchors
          draw(true,true);
      
      }else if(draggingImage){
      
          imageClick=false;
          
          mouseX=parseInt(e.clientX-offsetX);
          mouseY=parseInt(e.clientY-offsetY);
          
          // move the image by the amount of the latest drag
          var dx=mouseX-startX;
          var dy=mouseY-startY;
          imageX+=dx;
          imageY+=dy;
          imageRight+=dx;
          imageBottom+=dy;
          // reset the startXY for next time
          startX=mouseX;
          startY=mouseY;
          
          // redraw the image with border
          draw(false,true);
          
      }
      
      
    }


    $("#canvas").mousedown(function(e){handleMouseDown(e);});
    $("#canvas").mousemove(function(e){handleMouseMove(e);});
    $("#canvas").mouseup(function(e){handleMouseUp(e);});
    $("#canvas").mouseout(function(e){handleMouseOut(e);});

       
}); // end $(function(){});
</script>

</head>

<body>
    <p>Resize the image using the 4 draggable corner anchors</p>
    <p>You can also drag the image</p>
    <canvas id="canvas" width=350 height=350></canvas>
</body>
</html>

在 html5 画布上拖动和调整图像大小

问题描述

1 个解决方案

解决方案1
30 已采纳 2013-09-30 19:05:02

在 html5 画布上拖动和调整图像大小

问题描述

1 个解决方案

解决方案1 30 已采纳 2013-09-30 19:05:02

解决方案1
30 已采纳 2013-09-30 19:05:02