SubImage.cpp

/******************************************************************************
    QtAV:  Multimedia framework based on Qt and LibASS
    Copyright (C) 2012-2016 Wang Bin <wbsecg1@gmail.com>

*   This file is part of QtAV (from 2016)

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
******************************************************************************/
#include "QtAV/SubImage.h"
#include <QtGui/QImage>

namespace QtAV {

SubImage::SubImage(int x, int y, int w, int h, int stride)
    : x(x)
    , y(y)
    , w(w)
    , h(h)
    , stride(stride)
{}

SubImageSet::SubImageSet(int width, int height, Format format)
    : fmt(format)
    , w(width)
    , h(height)
    , id(0)
{}


#define _r(c)  ((c)>>24)
#define _g(c)  (((c)>>16)&0xFF)
#define _b(c)  (((c)>>8)&0xFF)
#define _a(c)  ((c)&0xFF)

#define qRgba2(r, g, b, a) ((a << 24) | (r << 16) | (g  << 8) | b)
/*
 * ASS_Image: 1bit alpha per pixel + 1 rgb per image. less memory usage
 */
//0xAARRGGBB
#if (Q_BYTE_ORDER == Q_BIG_ENDIAN)
#define ARGB32_SET(C, R, G, B, A) \
    C[0] = (A); \
    C[1] = (R); \
    C[2] = (G); \
    C[3] = (B);
#define ARGB32_ADD(C, R, G, B, A) \
    C[0] += (A); \
    C[1] += (R); \
    C[2] += (G); \
    C[3] += (B);
#define ARGB32_A(C) (C[0])
#define ARGB32_R(C) (C[1])
#define ARGB32_G(C) (C[2])
#define ARGB32_B(C) (C[3])
#else
#define ARGB32_SET(C, R, G, B, A) \
    C[0] = (B); \
    C[1] = (G); \
    C[2] = (R); \
    C[3] = (A);
#define ARGB32_ADD(C, R, G, B, A) \
    C[0] += (B); \
    C[1] += (G); \
    C[2] += (R); \
    C[3] += (A);
#define ARGB32_A(C) (C[3])
#define ARGB32_R(C) (C[2])
#define ARGB32_G(C) (C[1])
#define ARGB32_B(C) (C[0])
#endif
#define USE_QRGBA 0
// C[i] = C'[i] = (k*c[i]+(255-k)*C[i])/255 = C[i] + k*(c[i]-C[i])/255, min(c[i],C[i]) <= C'[i] <= max(c[i],C[i])

// render 1 ass image into a 32bit QImage with alpha channel.
//use dstX, dstY instead of img->dst_x/y because image size is small then ass renderer size
void RenderASS(QImage *image, const SubImage& img, int dstX, int dstY)
{
    const quint8 a = 255 - _a(img.color);
    if (a == 0)
        return;
    const quint8 r = _r(img.color);
    const quint8 g = _g(img.color);
    const quint8 b = _b(img.color);
    const quint8 *src = (const quint8*)img.data.constData();
    // use QRgb to avoid endian issue
    QRgb *dst = (QRgb*)image->constBits() + dstY * image->width() + dstX;
    // k*src+(1-k)*dst
    for (int y = 0; y < img.h; ++y) {
        for (int x = 0; x < img.w; ++x) {
            const unsigned k = ((unsigned) src[x])*a/255;
#if USE_QRGBA
            const unsigned A = qAlpha(dst[x]);
#else
            quint8 *c = (quint8*)(&dst[x]);
            const unsigned A = ARGB32_A(c);
#endif
            if (A == 0) { // dst color can be ignored
#if USE_QRGBA
                 dst[x] = qRgba(r, g, b, k);
#else
                 ARGB32_SET(c, r, g, b, k);
#endif //USE_QRGBA
            } else if (k == 0) { //no change
                //dst[x] = qRgba(qRed(dst[x])), qGreen(dst[x]), qBlue(dst[x]), qAlpha(dst[x])) == dst[x];
            } else if (k == 255) {
#if USE_QRGBA
                dst[x] = qRgba(r, g, b, k);
#else
                ARGB32_SET(c, r, g, b, k);
#endif //USE_QRGBA
            } else {
                // c=k*dc/255=k*dc/256 * (1-1/256), -1<err(c) = k*dc/256^2<1, -1 is bad!
#if USE_QRGBA
                // no need to &0xff because always be 0~255
                dst[x] += qRgba2(k*(r-qRed(dst[x]))/255, k*(g-qGreen(dst[x]))/255, k*(b-qBlue(dst[x]))/255, k*(a-A)/255);
#else
                const unsigned R = ARGB32_R(c);
                const unsigned G = ARGB32_G(c);
                const unsigned B = ARGB32_B(c);
                ARGB32_ADD(c, r == R ? 0 : k*(r-R)/255, g == G ? 0 : k*(g-G)/255, b == B ? 0 : k*(b-B)/255, a == A ? 0 : k*(a-A)/255);
#endif
            }
        }
        src += img.stride;
        dst += image->width();
    }
}
} //namespace QtAV