/*
 * Copyright (c) 2011-2016, 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.struct.pyramid;

import boofcv.core.image.ImageGenerator;
import boofcv.core.image.inst.FactoryImageGenerator;
import boofcv.struct.image.ImageGray;

/**
 * <p>
 * Base class for image pyramids.  Provides common functionality and data structures.  The scale
 * is defined in its children {@link PyramidDiscrete} and {@link PyramidFloat}.  This allows
 * it to be either integer or floating point and strongly typed.
 * </p>
 *
 * <p>
 * When updating the pyramid, if the top most layer is at the same resolution as the original image then a reference
 * can optionally be saved, avoiding an unnecessary image copy.  This is done by setting the saveOriginalReference
 * to true.
 * </p>
 *
 * @author Peter Abeles
 */
@SuppressWarnings({"unchecked"})
public abstract class ImagePyramidBase<T extends ImageGray>
	implements ImagePyramid<T>
{
	// shape of full resolution input image
	protected int bottomWidth;
	protected int bottomHeight;

	// The image at different resolutions.  Larger indexes for lower resolutions
	public T layers[];

	// if the top layer is full resolution, should a copy be made or a reference to the original be saved?i
	protected boolean saveOriginalReference;

	// creates new images
	protected ImageGenerator<T> generator;

	/**
	 * Specifies input image size and behavior of top most layer.
	 *
	 * @param imageType Type of image which is processed
	 * @param saveOriginalReference If a reference to the full resolution image should be saved instead of copied.
	 */
	public ImagePyramidBase( Class<T> imageType , boolean saveOriginalReference ) {
		this.generator = FactoryImageGenerator.create(imageType);
		this.saveOriginalReference = saveOriginalReference;
	}

	/**
	 * Initializes internal data structures based on the input image's size.  Should be called each time a new image
	 * is processed.
	 * @param width Image width
	 * @param height Image height
	 */
	@Override
	public void initialize(int width, int height) {
		// see if it has already been initialized
		if( bottomWidth == width && bottomHeight == height )
			return;

		this.bottomWidth = width;
		this.bottomHeight = height;
		layers = generator.createArray(getNumLayers());
		double scaleFactor = getScale(0);

		if (scaleFactor == 1) {
			if (!saveOriginalReference) {
				layers[0] = generator.createInstance(bottomWidth, bottomHeight);
			}
		} else {
			layers[0] = generator.createInstance((int)Math.ceil(bottomWidth / scaleFactor), (int)Math.ceil(bottomHeight / scaleFactor));
		}

		for (int i = 1; i < layers.length; i++) {
			scaleFactor = getScale(i);
			layers[i] = generator.createInstance((int)Math.ceil(bottomWidth / scaleFactor), (int)Math.ceil(bottomHeight / scaleFactor));
		}
	}

	/**
	 * Used to internally check that the provided scales are valid.
	 */
	protected void checkScales() {
		if( getScale(0) < 0 ) {
			throw new IllegalArgumentException("The first layer must be more than zero.");
		}

		double prevScale = 0;
		for( int i = 0; i < getNumLayers(); i++ ) {
			double s = getScale(i);
			if( s < prevScale )
				throw new IllegalArgumentException("Higher layers must be the same size or larger than previous layers.");
			prevScale = s;
		}
	}

	@Override
	public void setTo(ImagePyramid<T> input) {
		for( int i = 0; i < layers.length; i++ ) {
			getLayer(i).setTo(input.getLayer(i));
		}
	}

	@Override
	public T getLayer(int layerNum) {
		return layers[layerNum];
	}

	public void setFirstLayer(T image) {
		if( saveOriginalReference ) {
			layers[0] = image;
		} else {
			throw new IllegalArgumentException("Attempting to set the first layer when saveOriginalReference is false");
		}
	}

	@Override
	public int getWidth(int layer) {
		return layers[layer].width;
	}

	@Override
	public int getHeight(int layer) {
		return layers[layer].height;
	}

	@Override
	public Class<T> getImageType() {
		return generator.getType();
	}

	@Override
	public int getInputWidth() {
		return bottomWidth;
	}

	@Override
	public int getInputHeight() {
		return bottomHeight;
	}

	public boolean isSaveOriginalReference() {
		return saveOriginalReference;
	}
}