基于HTML5的PACS--HTML5图像处理(7)实现客户端JS调整窗宽窗位

 1 //线性的window-leveling算法
 2 min = (2*windowCenter - windowWidth)/2.0 - 0.5;  
 3 max = (2*windowCenter + windowWidth)/2.0 - 0.5;
 4 for (var i = 0; i != nNumPixels; i++){
 5     showPixelValue = (pixelHuValue[i] - min)*255.0/(double)(max - min);
 6 } 
 7 //非线性的gamma算法
 8 min = (2*windowCenter - windowWidth)/2.0 - 0.5;  
 9 max = (2*windowCenter + windowWidth)/2.0 - 0.5;
10 for (var i = 0; i != nNumPixels; i++){
11     showPixelValue = 255.0 * Math.pow(pixelHuValue/(max-min), 1.0/gamma);
12 } 

  1 /**
  2  * @author http://www.cnblogs.com/poxiao
  3  * pixelBuffer代表是从后台获取到的像素信息数组，代码只列出了单色灰度图像的情况，
  4  * 如果是三色的RGB图像自己稍微改动下代码即可。篇幅有限不在叙述。
  5  **/
  6 var pixelBuffer;
  7 //width 代表图像的宽度，即DICOM中的标签(0028,0011)Columns
  8 var width;
  9 //height 代表图像的高度，即DICOM中的标签(0028,0010)Rows
 10 var height;
 11 /**
 12  * @windowCenter 代表当前要显示的窗位
 13  * @windowWidth 代表当前要显示的窗宽
 14  * @bitsStored (0028,0101) 根据每个像素的存储位数生成查找表大小
 15  * @rescaleSlope (0028,1053)用于计算HU值
 16  * @rescaleIntercept  (0028,1052)用于计算HU值
 17  * **/
 18 function createImageCanvas(windowCenter,windowWidth,bitsStored,rescaleSlope,rescaleIntercept){
 19     var lookupObject=new LookupTable();
 20     lookupObject.setData(windowCenter,windowWidth,bitsStored,rescaleSlope,rescaleIntercept);
 21     lookupObject.calculateHULookup();
 22     lookupObject.calculateLookup();
 23     
 24     var imageCanvas=document.createElement(‘canvas‘);
 25     imageCanvas.width = width;
 26     imageCanvas.height =height;
 27     imageCanvas.style.width = width;
 28     imageCanvas.style.height = height;
 29     var tmpCxt = imageCanvas.getContext(‘2d‘);
 30     var imageData = tmpCxt.getImageData(0,0,width,height);
 31     var n=0;
 32     for(var yPix=0; yPix<height; yPix++)
 33     {
 34         for(var xPix=0; xPix<width;xPix++)
 35         {
 36             var offset = (yPix * width + xPix) * 4;
 37             var pixelValue=lookupObject.lookup[pixelBuffer[n]];
 38             imageData.data[offset]=    pixelValue;
 39             imageData.data[offset+1]=pixelValue;
 40             imageData.data[offset+2]=pixelValue;
 41             imageData.data[offset+3]=255;
 42             n++;
 43         }
 44     }
 45     tmpCxt.putImageData(imageData, 0,0);
 46     
 47     return imageCanvas;
 48 };
 49 /**
 50  * 像素查找表，主要要先根据rescaleSlope和rescaleIntercept进行Hounsfield值的转换
 51  * HU[i] = pixel_val[i]*rescaleSlope+ rescaleIntercept
 52  */
 53 function LookupTable()
 54 {
 55     this.bitsStored;
 56     this.rescaleSlope;
 57     this.rescaleIntercept;
 58     this.windowCenter;
 59     this.windowWidth;
 60     
 61     this.huLookup;
 62     this.lookup;
 63 }
 64 
 65 LookupTable.prototype.setData=function(wc,ww,bs,rs,ri)
 66 {    
 67     this.windowCenter=wc;
 68     this.windowWidth=ww;
 69     this.bitsStored=bs;
 70     this.rescaleSlope=rs;
 71     this.rescaleIntercept=ri;
 72 };
 73 
 74 LookupTable.prototype.setWindowingdata=function(wc,ww)
 75 {
 76     this.windowCenter=wc;
 77     this.windowWidth=ww;
 78 };
 79 
 80 LookupTable.prototype.calculateHULookup=function()
 81 {
 82     var size=1<<this.bitsStored;
 83     this.huLookup = new Array(size);
 84     for(var inputValue=0;inputValue<size;inputValue++)
 85     {
 86         if(this.rescaleSlope == undefined && this.rescaleIntercept == undefined) {
 87             this.huLookup[inputValue] = inputValue;
 88         } else {       
 89             this.huLookup[inputValue] = inputValue * this.rescaleSlope + this.rescaleIntercept;
 90         }
 91     }
 92 };
 93 /**
 94  * 窗宽窗位的调整线性的Window-leveling算法
 95  * 非线性的gamma算法,稍微修改下：
 96  *  var y=255.0 * Math.pow(this.huLookup[inputValue]/this.windowWidth, 1.0/gamma);
 97  * **/
 98 LookupTable.prototype.calculateLookup=function()
 99 {    
100     var size=1<<this.bitsStored;
101     var min=this.windowCenter-0.5-(this.windowWidth-1)/2;
102     var max=this.windowCenter-0.5+(this.windowWidth-1)/2;
103     this.lookup=new Array(size);
104     for(var inputValue=0;inputValue<size;inputValue++)
105     {
106         if(this.huLookup[inputValue]<=min){
107             this.lookup[inputValue]=0 ;
108         }else if (this.huLookup[inputValue]>max){
109             this.lookup[inputValue]=255;
110         }else{                
111             var y=((this.huLookup[inputValue]-(this.windowCenter-0.5))/(this.windowWidth-1)+0.5)*255;
112             this.lookup[inputValue]= parseInt(y);
113         }
114     }
115 };