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Refactored LUTs to use typed arrays. Avoid reallocating window LUT.
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Relates to #34.
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@ivmartel
ivmartel committed Jul 8, 2013
1 parent 149fee7 commit a34bf43
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Showing 3 changed files with 82 additions and 122 deletions.
7 changes: 4 additions & 3 deletions src/dicom/dicomParser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -473,12 +473,13 @@ dwv.dicom.DicomParser.prototype.createImage = function()
image.setRescaleIntercept( parseFloat(this.dicomElements.RescaleIntercept.value[0]) );
}

// view
var view = new dwv.image.View(image);
// pixel representation
var isSigned = 0;
if( this.dicomElements.PixelRepresentation ) {
view.setIsSigned( this.dicomElements.PixelRepresentation.value[0] );
isSigned = this.dicomElements.PixelRepresentation.value[0];
}
// view
var view = new dwv.image.View(image, isSigned);
// window center and width
var windowPresets = [];
if( this.dicomElements.WindowCenter && this.dicomElements.WindowWidth ) {
Expand Down
181 changes: 74 additions & 107 deletions src/image/luts.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,116 +3,91 @@
*/
dwv.image = dwv.image || {};
/**
* @namespace Look Up Table (LUT) related.
* @namespace LookUp Table (LUT) related.
*/
dwv.image.lut = dwv.image.lut || {};

/**
* @class Rescale Lookup Table class.
* @class Rescale LUT class.
* @returns {Rescale}
*/
dwv.image.lut.Rescale = function(slope,intercept)
{
// default values if no presets
if(typeof(slope)==='undefined') slope = 1;
if(typeof(intercept)==='undefined') intercept = 0;
// Get the slope.
this.getSlope = function() { return slope; };
// Get the intercept.
this.getIntercept = function() { return intercept; };
// the internal array
var rescaleLut = [];
};

dwv.image.lut.Rescale.prototype.initialise = function(size)
{
if(typeof(size)==='undefined') size = 4096;
rescaleLut = new Array(size);
for(var i=0; i<size; ++i)
{
rescaleLut[i] = i * this.getSlope() + this.getIntercept();
}
};

dwv.image.lut.Rescale.prototype.getLength = function()
{
return rescaleLut.length;
};

dwv.image.lut.Rescale.prototype.getValue = function(offset)
{
return rescaleLut[offset];
dwv.image.lut.Rescale = function(slope_,intercept_)
{
// The internal array.
var rescaleLut_ = null;
// The rescale slope.
if(typeof(slope_) === 'undefined') slope_ = 1;
// The rescale intercept.
if(typeof(intercept_) === 'undefined') intercept_ = 0;

// Get the rescale slope.
this.getSlope = function() { return slope_; };
// Get the rescale intercept.
this.getIntercept = function() { return intercept_; };
// Initialise the LUT.
this.initialise = function(size)
{
if(typeof(size) === 'undefined') size = 4096;
rescaleLut_ = new Float32Array(size);
for(var i=0; i<size; ++i)
rescaleLut_[i] = i * slope_ + intercept_;
};
// Get the length of the LUT array.
this.getLength = function() { return rescaleLut_.length; };
// Get the value of the LUT at the given offset.
this.getValue = function(offset) { return rescaleLut_[offset]; };
};

/**
* @class Window Lookup Table class.
* @class Window LUT class.
* @returns {Window}
*/
dwv.image.lut.Window = function(center, width, rescaleLut, isSigned)
{
// default values if no presets
if(typeof(center)==='undefined') center = 100;
if(typeof(width)==='undefined') width = 200;
dwv.image.lut.Window = function(rescaleLut_, isSigned_)
{
// The internal array: Uint8ClampedArray clamps between 0 and 255.
var windowLut_ = new Uint8ClampedArray(rescaleLut_.getLength());
// The window center.
var center_ = null;
// The window width.
var width_ = null;

// Get the center.
this.getCenter = function() { return center; };
this.getCenter = function() { return center_; };
// Get the width.
this.getWidth = function() { return width; };
// Get the rescale LUT.
this.getRescaleLut = function() { return rescaleLut; };
// Get the signed flag
this.isSigned = function() { return isSigned; };
// the internal array
var windowLut = [];
};

dwv.image.lut.Window.prototype.initialise = function(size)
{
if(typeof(size)==='undefined') size = this.getRescaleLut().getLength();

var center = this.getCenter() - 0.5;
if( this.isSigned() ) center += size/2;
var width = this.getWidth() - 1;

var xMin = center - width / 2;
var xMax = center + width / 2;
var yMax = 255;
var yMin = 0;

windowLut = new Array(size);
var y = 0;
var value = 0;
for(var i=0; i<size; i++)
{
value = this.getRescaleLut().getValue(i);
if(value <= xMin)
{
windowLut[i] = yMin;
}
else if (value > xMax)
this.getWidth = function() { return width_; };
// Get the signed flag.
this.isSigned = function() { return isSigned_; };
// Set the window center and width.
this.setCenterAndWidth = function(center, width)
{
// store the window values
center_ = center;
width_ = width;
// pre calculate loop values
var size = windowLut_.length;
var center0 = isSigned_ ? center - 0.5 + size / 2 : center - 0.5;
var width0 = width - 1;
// Uint8ClampedArray clamps between 0 and 255
var dispval = 0;
for(var i=0; i<size; ++i)
{
windowLut[i] = yMax;
// from the DICOM specification (https://www.dabsoft.ch/dicom/3/C.11.2.1.2/)
// y = ((x - (c - 0.5)) / (w-1) + 0.5) * (ymax - ymin )+ ymin
dispval = ((rescaleLut_.getValue(i) - center0 ) / width0 + 0.5) * 255;
windowLut_[i]= parseInt(dispval, 10);
}
else
{
y = ( (value - center ) / width + 0.5 ) * (yMax-yMin) + yMin;
windowLut[i]= parseInt(y, 10);
}
}
};

dwv.image.lut.Window.prototype.getLength = function()
{
return windowLut.length;
};
};
// Get the length of the LUT array.
this.getLength = function() { return windowLut_.length; };
// Get the value of the LUT at the given offset.
this.getValue = function(offset)
{
var shift = isSigned_ ? windowLut_.length / 2 : 0;
return windowLut_[offset+shift];
};

dwv.image.lut.Window.prototype.getValue = function(offset)
{
var shift = 0;
if( this.isSigned() ) shift = windowLut.length/2;
return windowLut[offset+shift];
};


/**
* Lookup tables for image color display.
*/
Expand All @@ -122,9 +97,8 @@ dwv.image.lut.range_max = 256;
dwv.image.lut.buildLut = function(func)
{
var lut = [];
for( var i=0; i<dwv.image.lut.range_max; ++i ) {
for( var i=0; i<dwv.image.lut.range_max; ++i )
lut.push(func(i));
}
return lut;
};

Expand All @@ -135,35 +109,31 @@ dwv.image.lut.max = function(i)

dwv.image.lut.maxFirstThird = function(i)
{
if( i < dwv.image.lut.range_max/3 ) {
if( i < dwv.image.lut.range_max/3 )
return dwv.image.lut.range_max-1;
}
return 0;
};

dwv.image.lut.maxSecondThird = function(i)
{
var third = dwv.image.lut.range_max/3;
if( i >= third && i < 2*third ) {
if( i >= third && i < 2*third )
return dwv.image.lut.range_max-1;
}
return 0;
};

dwv.image.lut.maxThirdThird = function(i)
{
if( i >= 2*dwv.image.lut.range_max/3 ) {
if( i >= 2*dwv.image.lut.range_max/3 )
return dwv.image.lut.range_max-1;
}
return 0;
};

dwv.image.lut.toMaxFirstThird = function(i)
{
var val = i * 3;
if( val > dwv.image.lut.range_max-1 ) {
if( val > dwv.image.lut.range_max-1 )
return dwv.image.lut.range_max-1;
}
return val;
};

Expand All @@ -173,9 +143,8 @@ dwv.image.lut.toMaxSecondThird = function(i)
var val = 0;
if( i >= third ) {
val = (i-third) * 3;
if( val > dwv.image.lut.range_max-1 ) {
if( val > dwv.image.lut.range_max-1 )
return dwv.image.lut.range_max-1;
}
}
return val;
};
Expand All @@ -186,9 +155,8 @@ dwv.image.lut.toMaxThirdThird = function(i)
var val = 0;
if( i >= 2*third ) {
val = (i-2*third) * 3;
if( val > dwv.image.lut.range_max-1 ) {
if( val > dwv.image.lut.range_max-1 )
return dwv.image.lut.range_max-1;
}
}
return val;
};
Expand Down Expand Up @@ -249,4 +217,3 @@ dwv.image.lut.test = {
"green": dwv.image.lut.buildLut(dwv.image.lut.id),
"blue": dwv.image.lut.buildLut(dwv.image.lut.id)
};*/

16 changes: 4 additions & 12 deletions src/image/view.js
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Original file line number Diff line number Diff line change
Expand Up @@ -9,20 +9,18 @@ dwv.image = dwv.image || {};
* Need to set the window lookup table once created
* (either directly or with helper methods).
*/
dwv.image.View = function(image)
dwv.image.View = function(image, isSigned)
{
// rescale lookup table
var rescaleLut = new dwv.image.lut.Rescale(
image.getRescaleSlope(), image.getRescaleIntercept() );
rescaleLut.initialise();
// window lookup table
var windowLut = null;
var windowLut = new dwv.image.lut.Window(rescaleLut, isSigned);
// window presets
var windowPresets = null;
// color map
var colorMap = dwv.image.lut.plain;
// is signed flag
var isSigned = 0;
// current position
var currentPosition = {"i":0,"j":0,"k":0};

Expand Down Expand Up @@ -60,8 +58,6 @@ dwv.image.View = function(image)
};
// Is the data signed data.
this.isSigned = function() { return isSigned; };
// Set the signed data flag.
this.setIsSigned = function(value) { isSigned = value; };
// Get the current position.
this.getCurrentPosition = function() { return currentPosition; };
// Set the current position. Returns false if not in bounds.
Expand Down Expand Up @@ -95,12 +91,8 @@ dwv.image.View = function(image)
*/
dwv.image.View.prototype.setWindowLevel = function( center, width )
{
var lut = new dwv.image.lut.Window(center, width, this.getRescaleLut(), this.isSigned());
lut.initialise();
this.setWindowLut( lut );
this.fireEvent({"type": "wlchange",
"wc": lut.getCenter(),
"ww": lut.getWidth() });
this.getWindowLut().setCenterAndWidth(center, width);
this.fireEvent({"type": "wlchange", "wc": center, "ww": width });
};

/**
Expand Down

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