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BoofCV is an open source Java library for real-time computer vision and robotics applications.
There is a newer version: 1.1.7
/*
 * Copyright (c) 2011-2019, Peter Abeles. All Rights Reserved.
 *
 * This file is part of BoofCV (http://boofcv.org).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package boofcv.abst.feature.describe;

import boofcv.BoofDefaults;
import boofcv.alg.feature.describe.DescribePointSift;
import boofcv.alg.feature.detect.interest.SiftScaleSpace;
import boofcv.alg.feature.detect.interest.UnrollSiftScaleSpaceGradient;
import boofcv.core.image.GConvertImage;
import boofcv.struct.feature.TupleDesc_F64;
import boofcv.struct.image.GrayF32;
import boofcv.struct.image.ImageGray;
import boofcv.struct.image.ImageType;

/**
 * Allows you to use SIFT features independent of the SIFT detector.  A SIFT scale-space is computed with all octaves
 * and most of the scales saved.  When a few feature is requested it looks up the closest scale image and uses
 * that as the input image.
 *
 * @author Peter Abeles
 */
public class DescribeRegionPoint_SIFT >
	implements DescribeRegionPoint
{
	// expected type of input image.  All image types are converted to floats since that's what
	// the scale-space requires
	ImageType imageType;

	// precomputes the entire scale-space gradient for faster lookup later
	UnrollSiftScaleSpaceGradient scaleSpace;

	// computes the feature description
	DescribePointSift describe;

	// used as temporary storage for the input image if it needs to be converted
	GrayF32 imageFloat = new GrayF32(1,1);

	public DescribeRegionPoint_SIFT(SiftScaleSpace scaleSpace,
									DescribePointSift describe,
									Class imageType ) {
		this.scaleSpace = new UnrollSiftScaleSpaceGradient(scaleSpace);
		this.describe = describe;

		this.imageType = ImageType.single(imageType);
	}

	@Override
	public void setImage(T image) {
		GrayF32 input;
		if( image instanceof GrayF32) {
			input = (GrayF32)image;
		} else {
			imageFloat.reshape(image.width,image.height);
			GConvertImage.convert(image,imageFloat);
			input = imageFloat;
		}

		scaleSpace.setImage(input);
	}

	@Override
	public boolean process(double x, double y, double orientation, double radius, TupleDesc_F64 description) {

		// get the blur sigma for the radius
		double sigma = radius / BoofDefaults.SIFT_SCALE_TO_RADIUS;

		// find the image which the blur factor closest to this sigma
		UnrollSiftScaleSpaceGradient.ImageScale image = scaleSpace.lookup(sigma);

		// compute the descriptor
		describe.setImageGradient(image.derivX,image.derivY);
		describe.process(x/image.imageToInput,y/image.imageToInput,sigma/image.imageToInput,
				orientation,description);

		return true;
	}

	@Override
	public boolean requiresRadius() {
		return true;
	}

	@Override
	public boolean requiresOrientation() {
		return true;
	}

	@Override
	public ImageType getImageType() {
		return imageType;
	}

	@Override
	public double getCanonicalWidth() {
		return describe.getCanonicalRadius()*2;
	}

	@Override
	public TupleDesc_F64 createDescription() {
		return new TupleDesc_F64(describe.getDescriptorLength());
	}

	@Override
	public Class getDescriptionType() {
		return TupleDesc_F64.class;
	}
}