OgreImageResampler.h

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/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2014 Torus Knot Software Ltd

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-----------------------------------------------------------------------------
*/
#ifndef OGREIMAGERESAMPLER_H
#define OGREIMAGERESAMPLER_H

#include <algorithm>

// this file is inlined into OgreImage.cpp!
// do not include anywhere else.
namespace Ogre {
// variable name hints:
// sx_48 = 16/48-bit fixed-point x-position in source
// stepx = difference between adjacent sx_48 values
// sx1 = lower-bound integer x-position in source
// sx2 = upper-bound integer x-position in source
// sxf = fractional weight between sx1 and sx2
// x,y,z = location of output pixel in destination

// nearest-neighbor resampler, does not convert formats.
// templated on bytes-per-pixel to allow compiler optimizations, such
// as simplifying memcpy() and replacing multiplies with bitshifts
template<unsigned int elemsize> struct NearestResampler {
    static void scale(const PixelBox& src, const PixelBox& dst) {
        // assert(src.format == dst.format);

        // srcdata stays at beginning, pdst is a moving pointer
        uchar* srcdata = (uchar*)src.getTopLeftFrontPixelPtr();
        uchar* pdst = (uchar*)dst.getTopLeftFrontPixelPtr();

        // sx_48,sy_48,sz_48 represent current position in source
        // using 16/48-bit fixed precision, incremented by steps
        uint64 stepx = ((uint64)src.getWidth() << 48) / dst.getWidth();
        uint64 stepy = ((uint64)src.getHeight() << 48) / dst.getHeight();
        uint64 stepz = ((uint64)src.getDepth() << 48) / dst.getDepth();

        // note: ((stepz>>1) - 1) is an extra half-step increment to adjust
        // for the center of the destination pixel, not the top-left corner
        uint64 sz_48 = (stepz >> 1) - 1;
        for (size_t z = dst.front; z < dst.back; z++, sz_48 += stepz) {
            size_t srczoff = (size_t)(sz_48 >> 48) * src.slicePitch;
            
            uint64 sy_48 = (stepy >> 1) - 1;
            for (size_t y = dst.top; y < dst.bottom; y++, sy_48 += stepy) {
                size_t srcyoff = (size_t)(sy_48 >> 48) * src.rowPitch;
            
                uint64 sx_48 = (stepx >> 1) - 1;
                for (size_t x = dst.left; x < dst.right; x++, sx_48 += stepx) {
                    uchar* psrc = srcdata +
                        elemsize*((size_t)(sx_48 >> 48) + srcyoff + srczoff);
                    memcpy(pdst, psrc, elemsize);
                    pdst += elemsize;
                }
                pdst += elemsize*dst.getRowSkip();
            }
            pdst += elemsize*dst.getSliceSkip();
        }
    }
};


// default floating-point linear resampler, does format conversion
struct LinearResampler {
    static void scale(const PixelBox& src, const PixelBox& dst) {
        size_t srcelemsize = PixelUtil::getNumElemBytes(src.format);
        size_t dstelemsize = PixelUtil::getNumElemBytes(dst.format);

        // srcdata stays at beginning, pdst is a moving pointer
        uchar* srcdata = (uchar*)src.getTopLeftFrontPixelPtr();
        uchar* pdst = (uchar*)dst.getTopLeftFrontPixelPtr();
        
        // sx_48,sy_48,sz_48 represent current position in source
        // using 16/48-bit fixed precision, incremented by steps
        uint64 stepx = ((uint64)src.getWidth() << 48) / dst.getWidth();
        uint64 stepy = ((uint64)src.getHeight() << 48) / dst.getHeight();
        uint64 stepz = ((uint64)src.getDepth() << 48) / dst.getDepth();
        
        // note: ((stepz>>1) - 1) is an extra half-step increment to adjust
        // for the center of the destination pixel, not the top-left corner
        uint64 sz_48 = (stepz >> 1) - 1;
        for (size_t z = dst.front; z < dst.back; z++, sz_48+=stepz) {
            // temp is 16/16 bit fixed precision, used to adjust a source
            // coordinate (x, y, or z) backwards by half a pixel so that the
            // integer bits represent the first sample (eg, sx1) and the
            // fractional bits are the blend weight of the second sample
            unsigned int temp = static_cast<unsigned int>(sz_48 >> 32);

            temp = (temp > 0x8000)? temp - 0x8000 : 0;
            uint32 sz1 = temp >> 16;                 // src z, sample #1
            uint32 sz2 = std::min(sz1+1,src.getDepth()-1);// src z, sample #2
            float szf = (temp & 0xFFFF) / 65536.f; // weight of sample #2

            uint64 sy_48 = (stepy >> 1) - 1;
            for (size_t y = dst.top; y < dst.bottom; y++, sy_48+=stepy) {
                temp = static_cast<unsigned int>(sy_48 >> 32);
                temp = (temp > 0x8000)? temp - 0x8000 : 0;
                uint32 sy1 = temp >> 16;                    // src y #1
                uint32 sy2 = std::min(sy1+1,src.getHeight()-1);// src y #2
                float syf = (temp & 0xFFFF) / 65536.f; // weight of #2
                
                uint64 sx_48 = (stepx >> 1) - 1;
                for (size_t x = dst.left; x < dst.right; x++, sx_48+=stepx) {
                    temp = static_cast<unsigned int>(sx_48 >> 32);
                    temp = (temp > 0x8000)? temp - 0x8000 : 0;
                    uint32 sx1 = temp >> 16;                    // src x #1
                    uint32 sx2 = std::min(sx1+1,src.getWidth()-1);// src x #2
                    float sxf = (temp & 0xFFFF) / 65536.f; // weight of #2
                
                    ColourValue x1y1z1, x2y1z1, x1y2z1, x2y2z1;
                    ColourValue x1y1z2, x2y1z2, x1y2z2, x2y2z2;

#define UNPACK(dst,x,y,z) PixelUtil::unpackColour(&dst, src.format, \
    srcdata + srcelemsize*((x)+(y)*src.rowPitch+(z)*src.slicePitch))

                    UNPACK(x1y1z1,sx1,sy1,sz1); UNPACK(x2y1z1,sx2,sy1,sz1);
                    UNPACK(x1y2z1,sx1,sy2,sz1); UNPACK(x2y2z1,sx2,sy2,sz1);
                    UNPACK(x1y1z2,sx1,sy1,sz2); UNPACK(x2y1z2,sx2,sy1,sz2);
                    UNPACK(x1y2z2,sx1,sy2,sz2); UNPACK(x2y2z2,sx2,sy2,sz2);
#undef UNPACK

                    ColourValue accum =
                        x1y1z1 * ((1.0f - sxf)*(1.0f - syf)*(1.0f - szf)) +
                        x2y1z1 * (        sxf *(1.0f - syf)*(1.0f - szf)) +
                        x1y2z1 * ((1.0f - sxf)*        syf *(1.0f - szf)) +
                        x2y2z1 * (        sxf *        syf *(1.0f - szf)) +
                        x1y1z2 * ((1.0f - sxf)*(1.0f - syf)*        szf ) +
                        x2y1z2 * (        sxf *(1.0f - syf)*        szf ) +
                        x1y2z2 * ((1.0f - sxf)*        syf *        szf ) +
                        x2y2z2 * (        sxf *        syf *        szf );

                    PixelUtil::packColour(accum, dst.format, pdst);

                    pdst += dstelemsize;
                }
                pdst += dstelemsize*dst.getRowSkip();
            }
            pdst += dstelemsize*dst.getSliceSkip();
        }
    }
};


// float32 linear resampler, converts FLOAT32_RGB/FLOAT32_RGBA only.
// avoids overhead of pixel unpack/repack function calls
struct LinearResampler_Float32 {
    static void scale(const PixelBox& src, const PixelBox& dst) {
        size_t srcchannels = PixelUtil::getNumElemBytes(src.format) / sizeof(float);
        size_t dstchannels = PixelUtil::getNumElemBytes(dst.format) / sizeof(float);
        // assert(srcchannels == 3 || srcchannels == 4);
        // assert(dstchannels == 3 || dstchannels == 4);

        // srcdata stays at beginning, pdst is a moving pointer
        float* srcdata = (float*)src.getTopLeftFrontPixelPtr();
        float* pdst = (float*)dst.getTopLeftFrontPixelPtr();
        
        // sx_48,sy_48,sz_48 represent current position in source
        // using 16/48-bit fixed precision, incremented by steps
        uint64 stepx = ((uint64)src.getWidth() << 48) / dst.getWidth();
        uint64 stepy = ((uint64)src.getHeight() << 48) / dst.getHeight();
        uint64 stepz = ((uint64)src.getDepth() << 48) / dst.getDepth();
        
        // note: ((stepz>>1) - 1) is an extra half-step increment to adjust
        // for the center of the destination pixel, not the top-left corner
        uint64 sz_48 = (stepz >> 1) - 1;
        for (size_t z = dst.front; z < dst.back; z++, sz_48+=stepz) {
            // temp is 16/16 bit fixed precision, used to adjust a source
            // coordinate (x, y, or z) backwards by half a pixel so that the
            // integer bits represent the first sample (eg, sx1) and the
            // fractional bits are the blend weight of the second sample
            unsigned int temp = static_cast<unsigned int>(sz_48 >> 32);

            temp = (temp > 0x8000)? temp - 0x8000 : 0;
            uint32 sz1 = temp >> 16;                 // src z, sample #1
            uint32 sz2 = std::min(sz1+1,src.getDepth()-1);// src z, sample #2
            float szf = (temp & 0xFFFF) / 65536.f; // weight of sample #2

            uint64 sy_48 = (stepy >> 1) - 1;
            for (size_t y = dst.top; y < dst.bottom; y++, sy_48+=stepy) {
                temp = static_cast<unsigned int>(sy_48 >> 32);
                temp = (temp > 0x8000)? temp - 0x8000 : 0;
                uint32 sy1 = temp >> 16;                    // src y #1
                uint32 sy2 = std::min(sy1+1,src.getHeight()-1);// src y #2
                float syf = (temp & 0xFFFF) / 65536.f; // weight of #2
                
                uint64 sx_48 = (stepx >> 1) - 1;
                for (size_t x = dst.left; x < dst.right; x++, sx_48+=stepx) {
                    temp = static_cast<unsigned int>(sx_48 >> 32);
                    temp = (temp > 0x8000)? temp - 0x8000 : 0;
                    uint32 sx1 = temp >> 16;                    // src x #1
                    uint32 sx2 = std::min(sx1+1,src.getWidth()-1);// src x #2
                    float sxf = (temp & 0xFFFF) / 65536.f; // weight of #2
                    
                    // process R,G,B,A simultaneously for cache coherence?
                    float accum[4] = { 0.0f, 0.0f, 0.0f, 0.0f };

#define ACCUM3(x,y,z,factor) \
    { float f = factor; \
    size_t off = (x+y*src.rowPitch+z*src.slicePitch)*srcchannels; \
    accum[0]+=srcdata[off+0]*f; accum[1]+=srcdata[off+1]*f; \
    accum[2]+=srcdata[off+2]*f; }

#define ACCUM4(x,y,z,factor) \
    { float f = factor; \
    size_t off = (x+y*src.rowPitch+z*src.slicePitch)*srcchannels; \
    accum[0]+=srcdata[off+0]*f; accum[1]+=srcdata[off+1]*f; \
    accum[2]+=srcdata[off+2]*f; accum[3]+=srcdata[off+3]*f; }

                    if (srcchannels == 3 || dstchannels == 3) {
                        // RGB, no alpha
                        ACCUM3(sx1,sy1,sz1,(1.0f-sxf)*(1.0f-syf)*(1.0f-szf));
                        ACCUM3(sx2,sy1,sz1,      sxf *(1.0f-syf)*(1.0f-szf));
                        ACCUM3(sx1,sy2,sz1,(1.0f-sxf)*      syf *(1.0f-szf));
                        ACCUM3(sx2,sy2,sz1,      sxf *      syf *(1.0f-szf));
                        ACCUM3(sx1,sy1,sz2,(1.0f-sxf)*(1.0f-syf)*      szf );
                        ACCUM3(sx2,sy1,sz2,      sxf *(1.0f-syf)*      szf );
                        ACCUM3(sx1,sy2,sz2,(1.0f-sxf)*      syf *      szf );
                        ACCUM3(sx2,sy2,sz2,      sxf *      syf *      szf );
                        accum[3] = 1.0f;
                    } else {
                        // RGBA
                        ACCUM4(sx1,sy1,sz1,(1.0f-sxf)*(1.0f-syf)*(1.0f-szf));
                        ACCUM4(sx2,sy1,sz1,      sxf *(1.0f-syf)*(1.0f-szf));
                        ACCUM4(sx1,sy2,sz1,(1.0f-sxf)*      syf *(1.0f-szf));
                        ACCUM4(sx2,sy2,sz1,      sxf *      syf *(1.0f-szf));
                        ACCUM4(sx1,sy1,sz2,(1.0f-sxf)*(1.0f-syf)*      szf );
                        ACCUM4(sx2,sy1,sz2,      sxf *(1.0f-syf)*      szf );
                        ACCUM4(sx1,sy2,sz2,(1.0f-sxf)*      syf *      szf );
                        ACCUM4(sx2,sy2,sz2,      sxf *      syf *      szf );
                    }

                    memcpy(pdst, accum, sizeof(float)*dstchannels);

#undef ACCUM3
#undef ACCUM4

                    pdst += dstchannels;
                }
                pdst += dstchannels*dst.getRowSkip();
            }
            pdst += dstchannels*dst.getSliceSkip();
        }
    }
};



// byte linear resampler, does not do any format conversions.
// only handles pixel formats that use 1 byte per color channel.
// 2D only; punts 3D pixelboxes to default LinearResampler (slow).
// templated on bytes-per-pixel to allow compiler optimizations, such
// as unrolling loops and replacing multiplies with bitshifts
template<unsigned int channels> struct LinearResampler_Byte {
    static void scale(const PixelBox& src, const PixelBox& dst) {
        // assert(src.format == dst.format);

        // only optimized for 2D
        if (src.getDepth() > 1 || dst.getDepth() > 1) {
            LinearResampler::scale(src, dst);
            return;
        }

        // srcdata stays at beginning of slice, pdst is a moving pointer
        uchar* srcdata = (uchar*)src.getTopLeftFrontPixelPtr();
        uchar* pdst = (uchar*)dst.getTopLeftFrontPixelPtr();

        // sx_48,sy_48 represent current position in source
        // using 16/48-bit fixed precision, incremented by steps
        uint64 stepx = ((uint64)src.getWidth() << 48) / dst.getWidth();
        uint64 stepy = ((uint64)src.getHeight() << 48) / dst.getHeight();
        
        uint64 sy_48 = (stepy >> 1) - 1;
        for (size_t y = dst.top; y < dst.bottom; y++, sy_48+=stepy) {
            // bottom 28 bits of temp are 16/12 bit fixed precision, used to
            // adjust a source coordinate backwards by half a pixel so that the
            // integer bits represent the first sample (eg, sx1) and the
            // fractional bits are the blend weight of the second sample
            unsigned int temp = static_cast<unsigned int>(sy_48 >> 36);
            temp = (temp > 0x800)? temp - 0x800: 0;
            unsigned int syf = temp & 0xFFF;
            uint32 sy1 = temp >> 12;
            uint32 sy2 = std::min(sy1+1, src.bottom-src.top-1);
            size_t syoff1 = sy1 * src.rowPitch;
            size_t syoff2 = sy2 * src.rowPitch;

            uint64 sx_48 = (stepx >> 1) - 1;
            for (size_t x = dst.left; x < dst.right; x++, sx_48+=stepx) {
                temp = static_cast<unsigned int>(sx_48 >> 36);
                temp = (temp > 0x800)? temp - 0x800 : 0;
                unsigned int sxf = temp & 0xFFF;
                uint32 sx1 = temp >> 12;
                uint32 sx2 = std::min(sx1+1, src.right-src.left-1);

                unsigned int sxfsyf = sxf*syf;
                for (unsigned int k = 0; k < channels; k++) {
                    unsigned int accum =
                        srcdata[(sx1 + syoff1)*channels+k]*(0x1000000-(sxf<<12)-(syf<<12)+sxfsyf) +
                        srcdata[(sx2 + syoff1)*channels+k]*((sxf<<12)-sxfsyf) +
                        srcdata[(sx1 + syoff2)*channels+k]*((syf<<12)-sxfsyf) +
                        srcdata[(sx2 + syoff2)*channels+k]*sxfsyf;
                    // accum is computed using 8/24-bit fixed-point math
                    // (maximum is 0xFF000000; rounding will not cause overflow)
                    *pdst++ = static_cast<uchar>((accum + 0x800000) >> 24);
                }
            }
            pdst += channels*dst.getRowSkip();
        }
    }
};
}

#endif