three.js/examples/js/misc/VolumeSlice.js

( function () {

	/**
 * This class has been made to hold a slice of a volume data
 * @class
 * @param   {Volume} volume    The associated volume
 * @param   {number}       [index=0] The index of the slice
 * @param   {string}       [axis='z']      For now only 'x', 'y' or 'z' but later it will change to a normal vector
 * @see Volume
 */
	class VolumeSlice {

		constructor( volume, index, axis ) {

			const slice = this;
			/**
     * @member {Volume} volume The associated volume
     */
			this.volume = volume;
			/**
     * @member {Number} index The index of the slice, if changed, will automatically call updateGeometry at the next repaint
     */
			index = index || 0;
			Object.defineProperty( this, 'index', {
				get: function () {

					return index;

				},
				set: function ( value ) {

					index = value;
					slice.geometryNeedsUpdate = true;
					return index;

				}
			} );
			/**
     * @member {String} axis The normal axis
     */
			this.axis = axis || 'z';

			/**
     * @member {HTMLCanvasElement} canvas The final canvas used for the texture
     */
			/**
     * @member {CanvasRenderingContext2D} ctx Context of the canvas
     */
			this.canvas = document.createElement( 'canvas' );
			/**
     * @member {HTMLCanvasElement} canvasBuffer The intermediary canvas used to paint the data
     */
			/**
     * @member {CanvasRenderingContext2D} ctxBuffer Context of the canvas buffer
     */
			this.canvasBuffer = document.createElement( 'canvas' );
			this.updateGeometry();
			const canvasMap = new THREE.Texture( this.canvas );
			canvasMap.minFilter = THREE.LinearFilter;
			canvasMap.wrapS = canvasMap.wrapT = THREE.ClampToEdgeWrapping;
			const material = new THREE.MeshBasicMaterial( {
				map: canvasMap,
				side: THREE.DoubleSide,
				transparent: true
			} );
			/**
     * @member {Mesh} mesh The mesh ready to get used in the scene
     */
			this.mesh = new THREE.Mesh( this.geometry, material );
			this.mesh.matrixAutoUpdate = false;
			/**
     * @member {Boolean} geometryNeedsUpdate If set to true, updateGeometry will be triggered at the next repaint
     */
			this.geometryNeedsUpdate = true;
			this.repaint();

			/**
     * @member {Number} iLength Width of slice in the original coordinate system, corresponds to the width of the buffer canvas
     */

			/**
     * @member {Number} jLength Height of slice in the original coordinate system, corresponds to the height of the buffer canvas
     */

			/**
     * @member {Function} sliceAccess Function that allow the slice to access right data
     * @see Volume.extractPerpendicularPlane
     * @param {Number} i The first coordinate
     * @param {Number} j The second coordinate
     * @returns {Number} the index corresponding to the voxel in volume.data of the given position in the slice
     */

		}

		/**
   * @member {Function} repaint Refresh the texture and the geometry if geometryNeedsUpdate is set to true
   * @memberof VolumeSlice
   */
		repaint() {

			if ( this.geometryNeedsUpdate ) {

				this.updateGeometry();

			}

			const iLength = this.iLength,
				jLength = this.jLength,
				sliceAccess = this.sliceAccess,
				volume = this.volume,
				canvas = this.canvasBuffer,
				ctx = this.ctxBuffer;

			// get the imageData and pixel array from the canvas
			const imgData = ctx.getImageData( 0, 0, iLength, jLength );
			const data = imgData.data;
			const volumeData = volume.data;
			const upperThreshold = volume.upperThreshold;
			const lowerThreshold = volume.lowerThreshold;
			const windowLow = volume.windowLow;
			const windowHigh = volume.windowHigh;

			// manipulate some pixel elements
			let pixelCount = 0;
			if ( volume.dataType === 'label' ) {

				//this part is currently useless but will be used when colortables will be handled
				for ( let j = 0; j < jLength; j ++ ) {

					for ( let i = 0; i < iLength; i ++ ) {

						let label = volumeData[ sliceAccess( i, j ) ];
						label = label >= this.colorMap.length ? label % this.colorMap.length + 1 : label;
						const color = this.colorMap[ label ];
						data[ 4 * pixelCount ] = color >> 24 & 0xff;
						data[ 4 * pixelCount + 1 ] = color >> 16 & 0xff;
						data[ 4 * pixelCount + 2 ] = color >> 8 & 0xff;
						data[ 4 * pixelCount + 3 ] = color & 0xff;
						pixelCount ++;

					}

				}

			} else {

				for ( let j = 0; j < jLength; j ++ ) {

					for ( let i = 0; i < iLength; i ++ ) {

						let value = volumeData[ sliceAccess( i, j ) ];
						let alpha = 0xff;
						//apply threshold
						alpha = upperThreshold >= value ? lowerThreshold <= value ? alpha : 0 : 0;
						//apply window level
						value = Math.floor( 255 * ( value - windowLow ) / ( windowHigh - windowLow ) );
						value = value > 255 ? 255 : value < 0 ? 0 : value | 0;
						data[ 4 * pixelCount ] = value;
						data[ 4 * pixelCount + 1 ] = value;
						data[ 4 * pixelCount + 2 ] = value;
						data[ 4 * pixelCount + 3 ] = alpha;
						pixelCount ++;

					}

				}

			}

			ctx.putImageData( imgData, 0, 0 );
			this.ctx.drawImage( canvas, 0, 0, iLength, jLength, 0, 0, this.canvas.width, this.canvas.height );
			this.mesh.material.map.needsUpdate = true;

		}

		/**
   * @member {Function} Refresh the geometry according to axis and index
   * @see Volume.extractPerpendicularPlane
   * @memberof VolumeSlice
   */
		updateGeometry() {

			const extracted = this.volume.extractPerpendicularPlane( this.axis, this.index );
			this.sliceAccess = extracted.sliceAccess;
			this.jLength = extracted.jLength;
			this.iLength = extracted.iLength;
			this.matrix = extracted.matrix;
			this.canvas.width = extracted.planeWidth;
			this.canvas.height = extracted.planeHeight;
			this.canvasBuffer.width = this.iLength;
			this.canvasBuffer.height = this.jLength;
			this.ctx = this.canvas.getContext( '2d' );
			this.ctxBuffer = this.canvasBuffer.getContext( '2d' );
			if ( this.geometry ) this.geometry.dispose(); // dispose existing geometry

			this.geometry = new THREE.PlaneGeometry( extracted.planeWidth, extracted.planeHeight );
			if ( this.mesh ) {

				this.mesh.geometry = this.geometry;
				//reset mesh matrix
				this.mesh.matrix.identity();
				this.mesh.applyMatrix4( this.matrix );

			}

			this.geometryNeedsUpdate = false;

		}

	}

	THREE.VolumeSlice = VolumeSlice;

} )();