package com.lamfire.utils;

import java.awt.image.BufferedImage;

public class ImageScale {

    private int width;
    private int height;
    private int scaleWidth;
    double      support = (double) 3.0;
    double      PI      = (double) 3.14159265358978;
    double[]    contrib;
    double[]    normContrib;
    double[]    tmpContrib;
    int         startContrib, stopContrib;
    int         nDots;
    int         nHalfDots;

    /**
     * Start: Use Lanczos filter to replace the original algorithm for image scaling. Lanczos improves quality of the
     * scaled image
     */
    public BufferedImage zoomOut(BufferedImage srcBufferImage, int w, int h) {
        width = srcBufferImage.getWidth();
        height = srcBufferImage.getHeight();
        scaleWidth = w;

        if (determineResultSize(w, h) == 1) {
            return srcBufferImage;
        }
        calContrib();
        BufferedImage pbOut = gorizontalFiltering(srcBufferImage, w);
        BufferedImage pbFinalOut = verticalFiltering(pbOut, h);
        return pbFinalOut;
    }

    /**
     * ����ͼ��ߴ�
     */
    private int determineResultSize(int w, int h) {
        double scaleH, scaleV;
        scaleH = (double) w / (double) width;
        scaleV = (double) h / (double) height;
        // ��Ҫ�ж�һ��scaleH��scaleV�������Ŵ����
        if (scaleH >= 1.0 && scaleV >= 1.0) {
            return 1;
        }
        return 0;

    } // end of DetermineResultSize()

    private double lanczos(int i, int inWidth, int outWidth, double Support) {
        double x;

        x = (double) i * (double) outWidth / (double) inWidth;

        return Math.sin(x * PI) / (x * PI) * Math.sin(x * PI / Support) / (x * PI / Support);

    } // end of Lanczos()

    //
    // Assumption: same horizontal and vertical scaling factor
    //
    private void calContrib() {
        nHalfDots = (int) ((double) width * support / (double) scaleWidth);
        nDots = nHalfDots * 2 + 1;
        try {
            contrib = new double[nDots];
            normContrib = new double[nDots];
            tmpContrib = new double[nDots];
        } catch (Exception e) {
            System.out.println("init contrib,normContrib,tmpContrib" + e);
        }

        int center = nHalfDots;
        contrib[center] = 1.0;

        double weight = 0.0;
        int i = 0;
        for (i = 1; i <= center; i++) {
            contrib[center + i] = lanczos(i, width, scaleWidth, support);
            weight += contrib[center + i];
        }

        for (i = center - 1; i >= 0; i--) {
            contrib[i] = contrib[center * 2 - i];
        }

        weight = weight * 2 + 1.0;

        for (i = 0; i <= center; i++) {
            normContrib[i] = contrib[i] / weight;
        }

        for (i = center + 1; i < nDots; i++) {
            normContrib[i] = normContrib[center * 2 - i];
        }
    } // end of CalContrib()

    // �����Ե
    private void calTempContrib(int start, int stop) {
        double weight = 0;

        int i = 0;
        for (i = start; i <= stop; i++) {
            weight += contrib[i];
        }

        for (i = start; i <= stop; i++) {
            tmpContrib[i] = contrib[i] / weight;
        }

    } // end of CalTempContrib()

    private int getRedValue(int rgbValue) {
        int temp = rgbValue & 0x00ff0000;
        return temp >> 16;
    }

    private int getGreenValue(int rgbValue) {
        int temp = rgbValue & 0x0000ff00;
        return temp >> 8;
    }

    private int getBlueValue(int rgbValue) {
        return rgbValue & 0x000000ff;
    }

    private int comRGB(int redValue, int greenValue, int blueValue) {

        return (redValue << 16) + (greenValue << 8) + blueValue;
    }

    // ��ˮƽ�˲�
    private int horizontalFilter(BufferedImage bufImg, int startX, int stopX, int start, int stop, int y,
                                 double[] pContrib) {
        double valueRed = 0.0;
        double valueGreen = 0.0;
        double valueBlue = 0.0;
        int valueRGB = 0;
        int i, j;

        for (i = startX, j = start; i <= stopX; i++, j++) {
            valueRGB = bufImg.getRGB(i, y);

            valueRed += getRedValue(valueRGB) * pContrib[j];
            valueGreen += getGreenValue(valueRGB) * pContrib[j];
            valueBlue += getBlueValue(valueRGB) * pContrib[j];
        }

        valueRGB = comRGB(clip((int) valueRed), clip((int) valueGreen), clip((int) valueBlue));
        return valueRGB;

    } // end of HorizontalFilter()

    // ͼƬˮƽ�˲�
    private BufferedImage gorizontalFiltering(BufferedImage bufImage, int iOutW) {
        int dwInW = bufImage.getWidth();
        int dwInH = bufImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iOutW, dwInH, BufferedImage.TYPE_INT_RGB);

        for (int x = 0; x < iOutW; x++) {

            int startX;
            int start;
            int X = (int) (((double) x) * ((double) dwInW) / ((double) iOutW) + 0.5);
            int y = 0;

            startX = X - nHalfDots;
            if (startX < 0) {
                startX = 0;
                start = nHalfDots - X;
            } else {
                start = 0;
            }

            int stop;
            int stopX = X + nHalfDots;
            if (stopX > (dwInW - 1)) {
                stopX = dwInW - 1;
                stop = nHalfDots + (dwInW - 1 - X);
            } else {
                stop = nHalfDots * 2;
            }

            if (start > 0 || stop < nDots - 1) {
                calTempContrib(start, stop);
                for (y = 0; y < dwInH; y++) {
                    value = horizontalFilter(bufImage, startX, stopX, start, stop, y, tmpContrib);
                    pbOut.setRGB(x, y, value);
                }
            } else {
                for (y = 0; y < dwInH; y++) {
                    value = horizontalFilter(bufImage, startX, stopX, start, stop, y, normContrib);
                    pbOut.setRGB(x, y, value);
                }
            }
        }

        return pbOut;

    } // end of HorizontalFiltering()

    private int verticalFilter(BufferedImage pbInImage, int startY, int stopY, int start, int stop, int x,
                               double[] pContrib) {
        double valueRed = 0.0;
        double valueGreen = 0.0;
        double valueBlue = 0.0;
        int valueRGB = 0;
        int i, j;

        for (i = startY, j = start; i <= stopY; i++, j++) {
            valueRGB = pbInImage.getRGB(x, i);

            valueRed += getRedValue(valueRGB) * pContrib[j];
            valueGreen += getGreenValue(valueRGB) * pContrib[j];
            valueBlue += getBlueValue(valueRGB) * pContrib[j];
            // System.out.println(valueRed+"->"+Clip((int)valueRed)+"<-");
            //
            // System.out.println(valueGreen+"->"+Clip((int)valueGreen)+"<-");
            // System.out.println(valueBlue+"->"+Clip((int)valueBlue)+"<-"+"-->");
        }

        valueRGB = comRGB(clip((int) valueRed), clip((int) valueGreen), clip((int) valueBlue));
        // System.out.println(valueRGB);
        return valueRGB;

    } // end of VerticalFilter()

    private BufferedImage verticalFiltering(BufferedImage pbImage, int iOutH) {
        int iW = pbImage.getWidth();
        int iH = pbImage.getHeight();
        int value = 0;
        BufferedImage pbOut = new BufferedImage(iW, iOutH, BufferedImage.TYPE_INT_RGB);

        for (int y = 0; y < iOutH; y++) {

            int startY;
            int start;
            int Y = (int) (((double) y) * ((double) iH) / ((double) iOutH) + 0.5);

            startY = Y - nHalfDots;
            if (startY < 0) {
                startY = 0;
                start = nHalfDots - Y;
            } else {
                start = 0;
            }

            int stop;
            int stopY = Y + nHalfDots;
            if (stopY > (int) (iH - 1)) {
                stopY = iH - 1;
                stop = nHalfDots + (iH - 1 - Y);
            } else {
                stop = nHalfDots * 2;
            }

            if (start > 0 || stop < nDots - 1) {
                calTempContrib(start, stop);
                for (int x = 0; x < iW; x++) {
                    value = verticalFilter(pbImage, startY, stopY, start, stop, x, tmpContrib);
                    pbOut.setRGB(x, y, value);
                }
            } else {
                for (int x = 0; x < iW; x++) {
                    value = verticalFilter(pbImage, startY, stopY, start, stop, x, normContrib);
                    pbOut.setRGB(x, y, value);
                }
            }

        }

        return pbOut;

    } // end of VerticalFiltering()

    int clip(int x) {
        if (x < 0) return 0;
        if (x > 255) return 255;
        return x;
    }

    /**
     * End: Use Lanczos filter to replace the original algorithm for image scaling. Lanczos improves quality of the
     * scaled image
     */
}
