/*
    This file is a part of the KDE project

    Copyright © 2006 Zack Rusin <zack@kde.org>
    Copyright © 2006-2007, 2008 Fredrik Höglund <fredrik@kde.org>

    The stack blur algorithm was invented by Mario Klingemann <mario@quasimondo.com>

    This implementation is based on the version in Anti-Grain Geometry Version 2.4,
    Copyright © 2002-2005 Maxim Shemanarev (http://www.antigrain.com)

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <QPainter>
#include <QImage>
#include <QColor>
#include <QDebug>

#include <cmath>
#include <string.h>

#include "imagefilter.h"

using namespace khtml;

static const quint32 stack_blur8_mul[255] = {
    512, 512, 456, 512, 328, 456, 335, 512, 405, 328, 271, 456, 388, 335, 292, 512,
    454, 405, 364, 328, 298, 271, 496, 456, 420, 388, 360, 335, 312, 292, 273, 512,
    482, 454, 428, 405, 383, 364, 345, 328, 312, 298, 284, 271, 259, 496, 475, 456,
    437, 420, 404, 388, 374, 360, 347, 335, 323, 312, 302, 292, 282, 273, 265, 512,
    497, 482, 468, 454, 441, 428, 417, 405, 394, 383, 373, 364, 354, 345, 337, 328,
    320, 312, 305, 298, 291, 284, 278, 271, 265, 259, 507, 496, 485, 475, 465, 456,
    446, 437, 428, 420, 412, 404, 396, 388, 381, 374, 367, 360, 354, 347, 341, 335,
    329, 323, 318, 312, 307, 302, 297, 292, 287, 282, 278, 273, 269, 265, 261, 512,
    505, 497, 489, 482, 475, 468, 461, 454, 447, 441, 435, 428, 422, 417, 411, 405,
    399, 394, 389, 383, 378, 373, 368, 364, 359, 354, 350, 345, 341, 337, 332, 328,
    324, 320, 316, 312, 309, 305, 301, 298, 294, 291, 287, 284, 281, 278, 274, 271,
    268, 265, 262, 259, 257, 507, 501, 496, 491, 485, 480, 475, 470, 465, 460, 456,
    451, 446, 442, 437, 433, 428, 424, 420, 416, 412, 408, 404, 400, 396, 392, 388,
    385, 381, 377, 374, 370, 367, 363, 360, 357, 354, 350, 347, 344, 341, 338, 335,
    332, 329, 326, 323, 320, 318, 315, 312, 310, 307, 304, 302, 299, 297, 294, 292,
    289, 287, 285, 282, 280, 278, 275, 273, 271, 269, 267, 265, 263, 261, 259
};

static const quint32 stack_blur8_shr[255] = {
    9, 11, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17,
    17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19,
    19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20,
    20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24
};

inline static void blurHorizontal(QImage &image, unsigned int *stack, int div, int radius)
{
    int stackindex;
    int stackstart;

    quint32 *const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel;

    int w = image.width();
    int h = image.height();
    int wm = w - 1;

    unsigned int mul_sum = stack_blur8_mul[radius];
    unsigned int shr_sum = stack_blur8_shr[radius];

    unsigned int sum, sum_in, sum_out;

    for (int y = 0; y < h; y++) {
        sum     = 0;
        sum_in  = 0;
        sum_out = 0;

        const int yw = y * w;
        pixel = pixels[yw];
        for (int i = 0; i <= radius; i++) {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++) {
            pixel = pixels[yw + qMin(i, wm)];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum    += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        stackindex = radius;
        for (int x = 0, i = yw; x < w; x++) {
            pixels[i++] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            stackstart = stackindex + div - radius;
            if (stackstart >= div) {
                stackstart -= div;
            }

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[yw + qMin(x + radius + 1, wm)];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum    += sum_in;

            if (++stackindex >= div) {
                stackindex = 0;
            }

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in  -= *stackpix;
        } // for (x = 0, ...)
    } // for (y = 0, ...)
}

inline static void blurVertical(QImage &image, unsigned int *stack, int div, int radius)
{
    int stackindex;
    int stackstart;

    quint32 *const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel;

    int w = image.width();
    int h = image.height();
    int hm = h - 1;

    int mul_sum = stack_blur8_mul[radius];
    int shr_sum = stack_blur8_shr[radius];

    unsigned int sum, sum_in, sum_out;

    for (int x = 0; x < w; x++) {
        sum     = 0;
        sum_in  = 0;
        sum_out = 0;

        pixel = pixels[x];
        for (int i = 0; i <= radius; i++) {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++) {
            pixel = pixels[qMin(i, hm) * w + x];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum    += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        stackindex = radius;
        for (int y = 0, i = x; y < h; y++, i += w) {
            pixels[i] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            stackstart = stackindex + div - radius;
            if (stackstart >= div) {
                stackstart -= div;
            }

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[qMin(y + radius + 1, hm) * w + x];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum    += sum_in;

            if (++stackindex >= div) {
                stackindex = 0;
            }

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in  -= *stackpix;
        } // for (y = 0, ...)
    } // for (x = 0, ...)
}

static void stackBlur(QImage &image, float radius)
{
    radius = qRound(radius);

    int div = int(radius * 2) + 1;
    unsigned int *stack  = new unsigned int[div];

    blurHorizontal(image, stack, div, radius);
    blurVertical(image, stack, div, radius);

    delete [] stack;
}

void ImageFilter::shadowBlur(QImage &image, float radius, const QColor &color)
{
    if (radius < 0) {
        return;
    }

    if (radius > 0) {
        stackBlur(image, radius);
    }

    // Correct the color and opacity of the shadow
    QPainter p(&image);
    p.setCompositionMode(QPainter::CompositionMode_SourceIn);
    p.fillRect(image.rect(), color);
}

