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/* ============================================================
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* This file is a part of digiKam project
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* http://www.digikam.org
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* Description : A Sharpen threaded image filter.
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* Copyright (C) 2005-2010 by Gilles Caulier <caulier dot gilles at gmail dot com>
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* Original Sharpen algorithm copyright 2002
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* by Daniel M. Duley <mosfet@kde.org> from KImageEffect API.
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* This program is free software; you can redistribute it
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* and/or modify it under the terms of the GNU General
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* Public License as published by the Free Software Foundation;
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* either version 2, or (at your option)
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* ============================================================ */
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#define SQ2PI 2.50662827463100024161235523934010416269302368164062
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#define Epsilon 1.0e-12
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#include "sharpenfilter.h"
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SharpenFilter::SharpenFilter(DImg* orgImage, QObject* parent, double radius, double sigma)
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: DImgThreadedFilter(orgImage, parent, "Sharpen")
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SharpenFilter::SharpenFilter(DImgThreadedFilter* parentFilter,
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const DImg& orgImage, const DImg& destImage,
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int progressBegin, int progressEnd, double radius, double sigma)
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: DImgThreadedFilter(parentFilter, orgImage, destImage, progressBegin, progressEnd,
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parentFilter->filterName() + ": Sharpen")
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// We need to provide support for orgImage == destImage.
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// The algorithm does not support this out of the box, so use a temporary.
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if (orgImage.bits() == destImage.bits())
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m_destImage = DImg(destImage.width(), destImage.height(), destImage.sixteenBit());
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if (orgImage.bits() == destImage.bits())
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memcpy(destImage.bits(), m_destImage.bits(), m_destImage.numBytes());
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void SharpenFilter::filterImage()
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sharpenImage(m_radius, m_sigma);
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/** Function to apply the sharpen filter on an image*/
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void SharpenFilter::sharpenImage(double radius, double sigma)
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if (m_orgImage.isNull())
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kWarning() << "No image data available!";
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m_destImage = m_orgImage;
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double alpha, normalize=0.0;
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register long i=0, u, v;
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int kernelWidth = getOptimalKernelWidth(radius, sigma);
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int halfKernelWidth = kernelWidth / 2;
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if((int)m_orgImage.width() < kernelWidth)
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kWarning() << "Image is smaller than radius!";
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double *kernel = new double[kernelWidth*kernelWidth];
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kWarning() << "Unable to allocate memory!";
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for(v = -halfKernelWidth; v <= halfKernelWidth; ++v)
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for(u = -halfKernelWidth; u <= halfKernelWidth; ++u)
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alpha = exp(-((double) u*u+v*v)/(2.0*sigma*sigma));
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kernel[i] = alpha/(2.0*M_PI*sigma*sigma);
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normalize += kernel[i];
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kernel[i/2] = (-2.0)*normalize;
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convolveImage(kernelWidth, kernel);
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bool SharpenFilter::convolveImage(const unsigned int order, const double* kernel)
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int mx, my, sx, sy, mcx, mcy, progress;
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double red, green, blue, alpha, normalize=0.0;
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long halfKernelWidth = kernelWidth / 2;
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if((kernelWidth % 2) == 0)
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kWarning() << "Kernel width must be an odd number!";
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double *normal_kernel = new double[kernelWidth*kernelWidth];
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kWarning() << "Unable to allocate memory!";
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for(i=0 ; i < (kernelWidth*kernelWidth) ; ++i)
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normalize += kernel[i];
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if(fabs(normalize) <= Epsilon)
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normalize = 1.0/normalize;
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for(i=0 ; i < (kernelWidth*kernelWidth) ; ++i)
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normal_kernel[i] = normalize*kernel[i];
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double maxClamp = m_destImage.sixteenBit() ? 16777215.0 : 65535.0;
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for(y=0 ; !m_cancel && (y < m_destImage.height()) ; ++y)
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// FIXME: this calculation seems to be useless, since we already do it in the following loop
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// sy = y-halfKernelWidth;
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for(x=0 ; !m_cancel && (x < m_destImage.width()) ; ++x)
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red = green = blue = alpha = 0;
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sy = y-halfKernelWidth;
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for(mcy=0 ; !m_cancel && (mcy < kernelWidth) ; ++mcy, ++sy)
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my = sy < 0 ? 0 : sy > (int)m_destImage.height()-1 ? m_destImage.height()-1 : sy;
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sx = x+(-halfKernelWidth);
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for(mcx=0 ; !m_cancel && (mcx < kernelWidth) ; ++mcx, ++sx)
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mx = sx < 0 ? 0 : sx > (int)m_destImage.width()-1 ? m_destImage.width()-1 : sx;
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color = m_orgImage.getPixelColor(mx, my);
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red += (*k)*(color.red() * 257.0);
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green += (*k)*(color.green() * 257.0);
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blue += (*k)*(color.blue() * 257.0);
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alpha += (*k)*(color.alpha() * 257.0);
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red = red < 0.0 ? 0.0 : red > maxClamp ? maxClamp : red+0.5;
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green = green < 0.0 ? 0.0 : green > maxClamp ? maxClamp : green+0.5;
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blue = blue < 0.0 ? 0.0 : blue > maxClamp ? maxClamp : blue+0.5;
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alpha = alpha < 0.0 ? 0.0 : alpha > maxClamp ? maxClamp : alpha+0.5;
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m_destImage.setPixelColor(x, y, DColor((int)(red / 257UL), (int)(green / 257UL),
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(int)(blue / 257UL), (int)(alpha / 257UL),
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m_destImage.sixteenBit()));
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progress = (int)(((double)y * 100.0) / m_destImage.height());
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if ( progress%5 == 0 )
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postProgress( progress );
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delete [] normal_kernel;
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int SharpenFilter::getOptimalKernelWidth(double radius, double sigma)
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double normalize, value;
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return((int)(2.0*ceil(radius)+1.0));
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for(kernelWidth=5; ;)
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for(u=(-kernelWidth/2) ; u <= (kernelWidth/2) ; ++u)
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normalize += exp(-((double) u*u)/(2.0*sigma*sigma))/(SQ2PI*sigma);
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value = exp(-((double) u*u)/(2.0*sigma*sigma))/(SQ2PI*sigma)/normalize;
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if((long)(65535*value) <= 0)
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return((int)kernelWidth-2);
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} // namespace Digikam