/*
Copyright 2006 Jerry Huxtable

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 org.meteoinfo.image.filter;

import java.awt.image.BufferedImage;

/**
 * A filter which simulates the appearance of looking through glass. A separate
 * grayscale displacement image is provided and pixels in the source image are
 * displaced according to the gradient of the displacement map.
 */
public class DisplaceFilter extends TransformFilter {

    private float amount = 1;
    private BufferedImage displacementMap = null;
    private int[] xmap, ymap;
    private int dw, dh;

    public DisplaceFilter() {
    }

    /**
     * Set the displacement map.
     *
     * @param displacementMap an image representing the displacment at each
     * point
     * @see #getDisplacementMap
     */
    public void setDisplacementMap(BufferedImage displacementMap) {
        this.displacementMap = displacementMap;
    }

    /**
     * Get the displacement map.
     *
     * @return an image representing the displacment at each point
     * @see #setDisplacementMap
     */
    public BufferedImage getDisplacementMap() {
        return displacementMap;
    }

    /**
     * Set the amount of distortion.
     *
     * @param amount the amount min-value 0 max-value 1
     * @see #getAmount
     */
    public void setAmount(float amount) {
        this.amount = amount;
    }

    /**
     * Get the amount of distortion.
     *
     * @return the amount
     * @see #setAmount
     */
    public float getAmount() {
        return amount;
    }

    public BufferedImage filter(BufferedImage src, BufferedImage dst) {
        int w = src.getWidth();
        int h = src.getHeight();

        BufferedImage dm = displacementMap != null ? displacementMap : src;

        dw = dm.getWidth();
        dh = dm.getHeight();

        int[] mapPixels = new int[dw * dh];
        getRGB(dm, 0, 0, dw, dh, mapPixels);
        xmap = new int[dw * dh];
        ymap = new int[dw * dh];

        int i = 0;
        for (int y = 0; y < dh; y++) {
            for (int x = 0; x < dw; x++) {
                int rgb = mapPixels[i];
                int r = (rgb >> 16) & 0xff;
                int g = (rgb >> 8) & 0xff;
                int b = rgb & 0xff;
                mapPixels[i] = (r + g + b) / 8; // An arbitrary scaling factor which gives a good range for "amount"
                i++;
            }
        }

        i = 0;
        for (int y = 0; y < dh; y++) {
            int j1 = ((y + dh - 1) % dh) * dw;
            int j2 = y * dw;
            int j3 = ((y + 1) % dh) * dw;
            for (int x = 0; x < dw; x++) {
                int k1 = (x + dw - 1) % dw;
                int k2 = x;
                int k3 = (x + 1) % dw;
                xmap[i] = mapPixels[k1 + j1] + mapPixels[k1 + j2] + mapPixels[k1 + j3] - mapPixels[k3 + j1] - mapPixels[k3 + j2] - mapPixels[k3 + j3];
                ymap[i] = mapPixels[k1 + j3] + mapPixels[k2 + j3] + mapPixels[k3 + j3] - mapPixels[k1 + j1] - mapPixels[k2 + j1] - mapPixels[k3 + j1];
                i++;
            }
        }
        mapPixels = null;
        dst = super.filter(src, dst);
        xmap = ymap = null;
        return dst;
    }

    protected void transformInverse(int x, int y, float[] out) {
        float xDisplacement, yDisplacement;
        float nx = x;
        float ny = y;
        int i = (y % dh) * dw + x % dw;
        out[0] = x + amount * xmap[i];
        out[1] = y + amount * ymap[i];
    }

    public String toString() {
        return "Distort/Displace...";
    }
}
