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

import {
	ClampToEdgeWrapping,
	DoubleSide,
	LinearFilter,
	Mesh,
	MeshBasicMaterial,
	PlaneGeometry,
	Texture,
	SRGBColorSpace
} from 'three';

/**
 * This class has been made to hold a slice of a volume data
 * @class
 * @see Volume
 */
class VolumeSlice {

	/**
 	 * @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
	 */
	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 Texture( this.canvas );
		canvasMap.minFilter = LinearFilter;
		canvasMap.generateMipmaps = false;
		canvasMap.wrapS = canvasMap.wrapT = ClampToEdgeWrapping;
		canvasMap.colorSpace = SRGBColorSpace;
		const material = new MeshBasicMaterial( { map: canvasMap, side: DoubleSide, transparent: true } );
		/**
		 * @member {Mesh} mesh The mesh ready to get used in the scene
		 */
		this.mesh = new 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
		 */


	}

	/**
	 * 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;

	}

	/**
	 * 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 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;

	}

}

export { VolumeSlice };